Cyber-tourism

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There are so many places one might wish to visit for their scenery and physical geography, yet only limited resources and, of course, time.  The availability of high-resolution satellite images, together with free data that show variations in topographic elevation newly released from the Shuttle Radar Topography Mission, enables realistic simulations of just about anywhere.  William Bowen of the California State University has exploited this opportunity to give all-comers a view of most parts of the land surface, as if they were looking obliquely downwards from a high-altitude aircraft – geogdata.csun.edu/world_atlas/index.html

Mineral wealth

Although there are many glossy books about museum quality mineral specimens, as well as being expensive they often only cover a selection of those minerals known to science.  One of the beauties of the web is that a site can cram in as many pictures and ancillary data as its server permits, and anyone can browse what is on offer.  One such site has been set up by consulting geologist David Barthelmy, which not only illustrates more than 2000 different minerals (half the site’s content of 4300) but allows users to examine their molecular structure interactively – webmineral.com

After the tsunamis

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The main aftermath of Boxing Day is of course the millions of survivors, deeply traumatised, without their homes and possessions, short of food and clean water, and threatened by a host of diseases.  Second comes the spontaneous generosity of millions of ordinary, but more fortunate people, who within days deeply embarrassed mean-spirited politicians across the globe.  Then there are the aid agencies who responded to the unprecedented magnitude and breadth of the disaster.  How successful they will have been remains to be seen in the months ahead.  Finally, in the public arena, the media has effectively dropped the topic, and the death toll seems to have been capped at “more than 150 000”.  It will have been far, far greater than that, judging by the proportion of those reported missing to those whose death is confirmed, particularly for foreign tourists in the affected areas.  There comes a point, when the actual number becomes meaningless because of its size, as in the case of the Holocaust; 6 million Jews, maybe 20 million Russians.  There is of course an irresistible case for concentrating on the living and the future.  That is within the geoscientific sphere. 

That a tsunamis warning system failed to be established for the Indian Ocean when it was mooted can only be condemned in retrospect.  It is dreadful to contemplate the fact that Boxing Day did a lot of the work needed for risk assessment. It left kilometres-wide scars along all the affected coastlines, which geoscientists are already looking at to assess the mechanisms that either enhanced the power of the waves or, in a few cases, diminished them.  Geophysicists knew beforehand that submarine earthquakes of high magnitude affecting the Indian Ocean will likely occur only along the Sunda arc, so any future tsunamis will revisit the places already devastated this time.  There are environmental lessons too.  Coastlines stripped of their original mangrove swamps, for developments such as prawn farming, lost any protection.  Oddly, many environmentalists are decrying the destruction of habitats and pressuring for rehabilitation.  But this was a purely natural disaster, which over millennia will have happened again and again, before being restored to a temporary ecological balance.

So, it seems likely that measures to predict future Indian Ocean tsunamis will be put in place, with Thailand as the most likely centre.  Yet, seismologists fear that since the Sunda subduction system has failed once, after more than a century of muted activity, there may soon be further high-magnitude earthquakes.  Let us hope not.  As well as more rapid assessment of seismic magnitude, a warning system requires sea-floor pressure sensors to detect any major disturbance of ocean water, and careful modelling of how that is distributed by bathymetry.  Many fear that warnings that are not followed by actual events will induce the “crying wolf” response, and caution care in making warning.  The head of the Thai Meteorological service issued warnings following the announcement by the Pacific Tsunamis Warning Centre that a tsunamis had been unleashed in 1999.  Although it hit New Guinea and killed several thousand people there, it had no effect on Thailand, so he was dismissed.  He has campaigned for an Indian Ocean warning system since then, and has recently been reinstated.  When millions have been directly affected, and memory of the events of 26/12 will last for decades, it seems unlikely that “crying wolf” will result in much public outcry.

Warning system or not, the most pressing needs are for effective and swift communications in hazardous times, and for widespread education about what the hazards are and what to do when they are imminent.  Throughout the Pacific basin, even school children know what to do – head for high ground, especially if the sea goes down suddenly.  There have been fascinating reports of how the culture of ancient tribal people of the Andamans, probably living there for 20 thousand years or more, saved people.  A little girl saw ants swarming away from the sea on the fateful morning, and shouted to everyone to go inland.  That response may have been inculcated by previous tsunamis.  Communications across the affected region were indeed very poor in this case, largely because geoscientists who understood the risk when the magnitude and location of the earthquake became known did not know whom to contact in the Indian Ocean.  The answer is surely whoever issues weather forecasts, for most rural people have radios and listen to weather forecasts every day.

Sources:  Nature, 6, 20 and 27 January 2005 (see especially Schiermeier, Q. 2005.  On the trail of destruction. Nature, v. 433, p. 350-354.  This gives an outstanding, brief discussion of the processes involved in the disaster); New Scientist, 8 and 15 January 2005; Science, 14 January 2005 all contain substantial reports and some editorials.

A list of web links to maps, satellite images and other data relating to the Indian Ocean tsunamis has been assembled by David Stevens of the UN Office for Outer Space Affairs in Vienna.  After Friday 4th February, this can be accessed through UNOOSA’s  web page at www.oosa.unvienna.org/SAP/stdm.

World Conference on Disaster Reduction: words or action?

From 17 to 21 January 2005, delegates representing 168 states met to discuss measures to mitigate the effects of major disasters that have natural causes in Kobe, Japan.  The conference declaration designates 10 years for resolving the issues around predicting, warning of and responding to such events (the Hyogo Framework for Action 2005-2015).  A New Scientist editorial (Words will never save us.  New Scientist, 29 January 2005, p. 3) expressed caution about the fine words, because the actions needed are, in many fields, not well established.  Kobe did indeed concretise the intergovernmental pledge to establish not only an Indian Ocean tsunamis warning network, but one that will eventually cover all maritime countries.  It also highlighted the success of the Drought Early Warning service, that has a strong focus on Africa.  Yet time and again, the UN, EU and well heeled governments have been alerted to this long-lived kind of disaster, only to fail to respond in a way that truly mitigates the affects.  Drought-stricken people are kept barely alive by food aid, only to await the next failure of rains without the infrastructure to assist themselves.  New Scientist highlights the common factor in failing to survive natural calamities – poverty.  One thing characterised the response to Boxing Day: ordinary people everywhere took decisive action to help, financially and practically, thereby embarrassing and shaming their own governments, the “great and good” multinational institutions, and many an attendee at conference such as Kobe.

Wanna see an earthquake?

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Most of us have grown used to thinking that earthquakes have an epicentre at some fixed point beneath the surface. That is not at all true, as the event that set the Boxing Day 2004 tsunamis in motion as been shown to have been a lengthy rip that propagated from Sumatra NNE to the Nicobar Islands, over a period of about an hour.  Even quite small earthquakes are distributed and often migrate along a fault line.  Christine arson of the University of Colorado has captured what is effectively a movie of a magnitude 8.3 event off the island of Hokkaido, Japan, which can be viewed at spot.colorado.edu/~kristine/tokachi_rupture.gif. The data that she used comes from a network of  a thousand highly sensitive GPS receivers set up throughout Japan.  Instead of acceleration, measured by conventional seismometers, GPS records actual position in x, y, z coordinates.  That enable the actual motions to be imaged as in  the movie.

Evidence goes against end-Permian impact

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In December 2004 EPN commented on what appears to be a serious challenge to claims of geochemical evidence that would support a major impact associated with the largest of all mass extinctions in the Phanerozoic, that at the close of the Permian Period and the Palaeozoic Era, around 251 Ma ago.  Newly published analyses from two other well-constrained P-Tr boundary sites found no signs of the elements that would be expected from a major collision with a metal or silicate-rich asteroid (Koeberl, C. et al. 2004.  Geochemistry of the end-Permian extinction event in Austria and Italy: No evidence for an extraterrestrial component.  Geology, v. 32, p. 1053-1056).  Koeberl of the University of Vienna and colleagues from the US and UK focussed on platinum-group elements (PGEs), and osmium and helium isotopes. Both sites are stratigraphically similar and dominated by carbonate sediments, with evidence from one site for deepening water that laid down organic-rich marls.  Sure enough, there is a “spike” in iridium at the level of these marls, which had been documented at the Austrian site in 1989, and there is another 50 m higher in the sequence.  The new work confirmed both, and also found the marl-related “spike” in Italy. But the reason why iridium has been used to suggest extraterrestrial impacts is because, of all the PGEs, it is the easiest to analyse at very low concentrations. That can give rise to “false positives”, for there are purely terrestrial processes that can concentrate PGEs.  An unambiguous arbiter between these processes and impacts lies in the isotopic composition of the metal osmium.  Rocks of the Earth’s crust have high rhenium (Re) and low osmium (Os) contents, whereas in meteorites the Re/Os ratio is very much smaller.  The unstable isotope 187Re decays to produce a daughter 187Os that adds to the common 188Os isotope. Consequently, terrestrial rocks acquire high 187Os/!88Os rapidly after they crystallise from magmas and that “signature” is imparted to the entire surface environment through weathering and solution. On the other hand, meteorites have low 187Os/!88Os ratios, so the two influences on the geochemical record can be distinguished – if you have good enough analytical facilities.  The two iridium spikes fail that test, as regards an impact origin.  It seems likely that they originated through precipitation of PGEs from sea water under reducing conditions on the deep sea floor.  The helium isotope data carry the same negative message; they are typically terrestrial.

Impact-induced extinctions, particularly ones that wipe out a sizeable proportion of all organisms, are likely to be unremittingly sudden – direct effects being felt within hours over the whole planet, and secondary effects such as “nuclear winter” and acid rainfall over a matter of a few years or decades. Radiometric dating is incapable of resolving such short periods, and at the age of the P-Tr boundary probably not even several hundred millennia. Faunal sequences can give a better indication of abruptness. To most intents the marine record at the time does look as if extinction was very sharp, but it does not indicate anything by way of clear evidence for an impact, such as glass spherules, shocked quart grains and other tell-tale signs.  The continental record is pretty sparse, so has not figured much in the debate.  However, the Karoo basin of South Africa contains thick continental sediments that span the boundary, and is famous for its primitive reptile fauna, some of which became extinct around the time of the P-Tr event.  Incidentally, this die-off created the genetic conditions for the adaptive radiation in the Mesozoic that led not only to the dinosaurs but also the mammals and birds.  Charting the timing of the Karoo extinctions has proved difficult, although it appears not to have been sudden in a stratigraphic sense.  New age data has emerged from studies of palaeomagnetic field reversals in the sediments, together with variations in carbon isotopes, that allow timing to be better assessed through comparison with magnetic and carbon records from other sections (Ward, P.D. et al. 2005.  Abrupt and gradual extinction among Late Permian land vertebrates in the Karoo Basin, South Africa.  Science [soon to be published, currently available on Sciencexpress at www.sciencemag.org/sciencexpress/recent.shtml]).  The signs are that the proto-reptiles died off over tens to hundreds of thousand years due to some protracted crisis, probably connected with the giant continental flood basalt eruptions that formed the Siberian Traps. Those lavas overlap the timing of the P-Tr boundary, and would certainly have added sufficient CO2 to give substantial global warming and also massive emissions of SO2 that would have created chemically hazardous conditions on a global scale.

New predators on the Mesozoic block

Most people have been led to believe that, although the earliest mammals appeared in the Triassic fossil record, throughout the Mesozoic they were tiny and meekly scurried and skulked while the dinosaurs reigned supreme over land, sea and air.  They had to wait for the K-T extinction to develop their full ecological potential.  That is now a myth, for Chinese strata (yet again) have revealed much larger mammals than ever thought possible, and some of them ate dinosaurs (Hu, Y. et al. 2005.  Large Mesozoic mammals fed on young dinosaurs.  Nature, v. 433, p. 149-152).  One indisputable mammal skeleton contained the bones of young dinosaurs in its body cavity.  In fact so many that one wonders if it met its end through greed.

Interbreeding: louse study leads to head scratching

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A challenging question about the origin of fully modern humans is whether or not Homo sapiens interbred with archaic species, such as the Neanderthals or H. erectus.  That modern humans occupied the same territory as both, at the same time, is well established for Europe and Asia.  The likely time for the first major migration of moderns from Africa is about 70 to 100 thousand years ago, and archaic humans did not become extinct in Eurasia until 30 ka at the earliest.  Genetic material from extinct humans is rare and difficult to analyse because of degradation.  A couple of mtDNA samples from Neanderthal remains give results that are sufficiently different from ours to rule out retention in modern human populations of the genetic outcome of any interbreeding between ancestral moderns and the population to which the two Neanderthals belonged.  Yet it does not rule out such interactions with other archaic groups.  We have no idea of the genetic diversity of Neanderthals, whose lineage probably split from that of our own (through that of H. heidelburgensis) as long ago as 700 ka.  If they lived in isolated bands of a small population, that diversity could have become substantial over such a long time.    So far, no genetic material has been recovered from H. erectus remains.  Another approach to the matter has emerged from a genetic study of human head and body lice – Pediculus humanus (Reed DL. et al. 2004.  Genetic analysis of lice supports direct contact between modern and archaic humans. Public Library of Science Biology, v. 2, e340 – through www.plos.org). The louse Pediculus humanus is unique to humans, and genetic comparison with that which infests chimpanzees suggests that these two species diverged at about the same time as the split that led to modern humans and chimps, at about 5.6 Ma. That is remarkably similar to molecular timing that uses primate DNA.  The interesting feature of the louse genetic analyses by the team from the Universities of Florida, Utah and Glasgow is that there are differences between the lice that leap on us.  There are two strains which originated before 1 Ma ago, according to the molecular clock.  One has a global distribution, and infests both head and body, whereas the other is exclusively a head louse and only occurs in the Americas.

Around 1 Ma there seems also to have been a major divergence among early humans between a strand of H. erectus, which survived until as recently as 20 ka in Asia, and one that led to European Neanderthals and the modern humans who began to migrate from Africa to Eurasia around 100 ka.  The unique occurrence of the head-only louse in the Americas (along with the other strain) suggests that the modern humans who crossed the Bering Straits to colonise the Americas came into direct physical contact with beings who carried that particular strain, en route.  The likely candidates would have been Asian H. erectus.  Contact had to be direct, because, unlike the flea, the louse cannot leap, and it can only survive on humans.  The lack of the New World Pediculus humanus in Eurasia suggests two things: if moderns were “in touch” with archaics, the latter carried the other variant (Neanderthals?); the present Asian population (and that of New Guinea and Australia) possibly did not have close contact with archaics who were alive at the time of colonisation (were there by then very few?).  All very interesting, but it does not resolve the question of interbreeding; intimate contact could have been through fighting, trading or interbreeding.  There is another, very different human-only louse, Pthirus pubis, which infests pubic hair only, and about which there is very little genetic information, so far…

Mars, planet of 2004

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As 2004 was but a few days old, there was much cheering at NASA’s Jet Propulsion Laboratory as the two Mars landers touched down safely and unleashed the two Rovers to deploy their instruments.  Celebrations at ESA were not so universal, as the Beagle-2 miniature geochemistry laboratory vanished without trace.  Beagle could in principle have proved the existence or otherwise of Martian life, had it survived and landed on suitable ground.  Still, ESA’s Mars Express orbiter was safe and promised oodles of highly detailed pictures and other data.  What followed was an embarrassment of riches from both the US and EU missions, more or less throughout the year.  Then ESA had real cause for partying as 2005 opened, as its Huygens probe landed on the largest and most enigmatic moon in the solar system, Saturn’s Titan, but that is a story that will run this year, and it was carried courtesy of NASA’s Cassini mission.  New Scientist featured an excellent summary of the achievements on Mars in its 15th January 2005 issue (Chandler, D.L. 2005.  Distant shores.  New Scientist 15 January 2005, p. 30-39).  Everything has worked better than expected, Rovers Spirit and Discovery having the benefit of sand blasts that cleared the dust off their solar cells.  They are still functioning, though not exactly prancing – it has taken a year for them to travel just over 5 km between them.  But the treasures they have unfolded have delighted lots of geologists.  There is ample evidence at least for the former influence of liquid water at the surface, which has both weathered the Martian surface to produce iron minerals that witness both water and highly acid conditions and also laid down sediments in layer after layer.  Some hint at the former existence of a large shallow, salty sea where Discovery landed.  Mars Express’s imaging devices have produced high-resolution pictures that confirm the influence of water’s sculpting, seemingly late in its history, and the presence of recent glacial deposits.  The orbiter also carries a deeply penetrating radar device (MARSIS) capable of finding water up to a kilometre beneath the surface, though it has yet to be deployed.  Perhaps the most intriguing find is that Mars’ atmosphere has more methane in it than seems possible, unless something is continually emitting it.  That “something” could be volcanism (2004 also revealed signs of previously unknown, recent eruptions), methane may be leaking from sub-surface gas-hydrates similar to those beneath Earth’s sea floor, it could be emitted by icy material from comet debris, and maybe it signifies some primitive, methanogen life forms that are respiring.  The last needs to be tied down very rigorously before scientists get over excited.  Even if it matches up with signs of emitted water vapour, which it does, that could still be an abiogenic phenomenon.  There can be little doubt that Mars is proving irresistible as a political draw, riding on its kudos to hammer out the old message that “Man Must Go  There!”. But consider this: had today’s robotic technology and analytical miniaturisation been possible 35 years ago we would know vastly more than we do about the evolution of our neighbour the Moon.  Instead of carrying astronauts and their weighty life support systems, the Apollo missions would have brought back an equivalent mass of lunar rock.  The same goes for Mars, surely, on the old basis of getting “more bangs for your buck”.  But that is a scientific outlook, and maybe the bucks can only be raised by the romantic notion of some brave souls treading where Edgar Rice Burrough’s John Carter once rode astride his banth.  But of course, robotic science can also ride on that “vision”, for what could be more catastrophic to whichever US president succeeds in making George W. Bush’s dream come true to find that it is not safe enough out there, and the astronauts do not come back.

Plotting meteorite falls

Museums host collections of thousands of meteorites donated by collectors over more than a century.  Although they are the source of much of our understanding about the timing and processes involved in the origin of the solar system and of the Earth itself, the collections are biased towards those that are most easily spotted on the ground.  Metallic meteorites show up much more readily than do those made of silicate minerals, which resemble ordinary terrestrial rocks in colour and density.  Only when collectors pore over very uniform, light coloured surfaces, such as ice caps, deserts and bare limestone plateaux, can they be assured of a truly representative selection of types.   Also, many meteorite samples are weathered and contaminated with earthly materials, because they have lain around on the ground for a long time.  Improved precision and detection limits of the chemical analytical tools that meteorite specialists use demand fresh material, as do researchers interested in organic materials carried from space – the embarrassment of having an announcement of a fossil bacterium in a meteorite and then finding that it is some common bug from soil is career threatening.  Most important are trying to overcome the compositional bias and to see from which part of the sky different kinds of meteorite come.  Phil Bland of Imperial College, London is trying to solve all problems at a stroke.  His idea is to set up a network of wide-angle sky cameras to record meteor trails, so that computer analysis of the film will triangulate the point of impact and also work out the precise orbit of the offending body.  The ideal place – easy to get to, safe, flat, dry unvegetated and dominated by pale rock – is the infamous Nullarbor (“No Tree”) Plain of SW Australia, which is one of the most featureless places on Earth.  Bland already has one sky camera in place that has sensors that only turn it on if the sky is clear, and an internet connection that e-mails him if something as malfunctioned.  In one year it spotted 12 trails bright enough to have resulted in meteorites falling to the surface.  With three cameras, he hopes that results will be sufficiently accurate to narrow search areas to a square kilometre.  If funded, the extended project will even incorporate e-mail alerts to teams of local collectors, whenever a trail exceeds a certain brightness.  They should then be able to pristine recover material in a few days.

Source:  Muir, H. 2004.  Catch a falling star.  New Scientist, 25 December 2004, p. 45-47.

And was there a mighty wind?

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Readers will be familiar with the to-ing and fro-ing that surrounds the idea of Neoproterozoic Snowball Earth episodes from earlier issues of EPN.  The leading proponent and sturdy defender of the hypothesis, Paul Hoffman of Harvard University, re-enters the fray as co-author of a paper that builds on the idea that following global glaciation the climate became not only very warm but also violent (Allen, P.A. & Hoffman, P.F. 2005.  Extreme winds and waves in the aftermath of a Neoproterozoic glaciation.  Nature, v. 433, p. 123-127).  They document evidence from “cap carbonates” in northern Canada and Spitzbergen that succeed diamictites of “Marinoan” (~635 Ma) age, in the form of large-scale sedimentary structures.  Many of these are submarine ripples with amplitudes up to 40 cm, and forms that suggest they were produced by sea-bed motion due to surface waves, down to 200-400 m, far deeper than modern storm-wave base.  Central to their argument is hydrodynamic modelling of wind speeds that might have produced such large ripples, and their specific shapes – steep sided.  Being based on experiment and observation of modern sea-bed processes, the theory seems quite rigorous.  It retrodicts wave periods that are somewhat longer than those commonly seen in modern ocean storms.  From that they derive sustained wind speeds that exceed 70 km per hour across open oceans, extraordinary by modern ocean wind standards.

Another year passed

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Because of the horrific events at the end of 2004, this is not a time to celebrate geoscientific achievements during the year that has passed.

The horror of Boxing Day

Unlike the collapse of Manhattan’s Twin Towers on 11 September 2001 the world’s cameras were unable to focus on the minutiae of terrible events around the rim of the northern Indian Ocean.  They did not catch the sudden dawning of fear, but the tsunamis of 26 December 2004 were witnessed by millions of coast dwellers in Indonesia, SW Thailand, Sri Lanka, eastern India and as far away as Somalia, Tanzania and Kenya.  At the time of writing the death toll had reached 150 thousand, but it will rise inexorably, and countless people’s lives will be blighted for years to come.  The world did change on Boxing Day 2004 in a way that dwarfs the events of “9/11”.  The majority of those swept in minutes into a debris-loaded sea were among the poorest of their communities, and the dead are dominated by children and old people who simply did not have the strength to save themselves.  News came first from popular tourist resorts dotted on palm-fringed beaches, through cell phones and from hastily shot videos of what must at first have seemed a curiosity.  Before great waves appeared, the sea drew back to leave fish flapping on beaches, which local children rushed to gather as an unexpected benefice.  Ocean waves driven by great seismic events have immense wavelengths, so previously unseen sea floor lingered for 10 to 20 minutes before devastating surges suddenly rose above the horizon..

Off the western coast of Sumatra, a subduction-zone thrust displaced the sea floor by several metres, into which an unimaginable tonnage of ocean rushed.  Its rebound set in motion the most devastating natural phenomena, yet on the open ocean their passage would have been imperceptible because of their broad wavelength.  Unlike wind-waves, tsunamis travel extremely fast, around 400 km per hour; they are seismic disturbances affecting the entire water body.  The further they travel the greater the volume they affect, so they dissipate with distance.  Two days after the initial shock, sea-level rose perceptibly in California, half a world away.  When tsunamis meet shallows, the frictional effect causes the wave to slow, rise and steepen.  The wave breaks far offshore in shallow water, resulting in a surge that rises inexorably on land.  It rips up sea-floor materials, including boulders where they are present.  Damage and deaths result mainly from the backwash that can rip debris and victims several kilometres out to sea, until the next tsunami arrives, and in this case there were at least three.  We have all seen the aftermath, like nuclear devastation but not sterile.  Debris, rotting flesh and sewage breed disease, and as many may die from cholera, insect-borne disease and exposure as perished on Boxing Day morning.

The magnitude of the Sumatran sea-quake was 9.0 on the Richter Scale.  That is a logarithmic measure of the ground displacement, so that for every increase of 1.0 in magnitude ground motion increases by 10 times.  However, it is the energy released that damages and the corresponding increase is 32 times.  The Sumatran sea-quake was the largest recorded since that off Alaska in 1964 (magnitude 9.2) and the fourth largest in a century.  Tsunamis generated off Alaska reached a height of over 60 metres close to the epicentre, but they travelled parallel to the coast of the Americas and caused only 130 deaths.  Those of 26 December 2004 hit land head on, and there are large, densely populated coastal tracts around the Indian Ocean that are below 10 m above mean sea level.  Buildings, particularly for poor people, are fragile and lightweight, so the devastation was almost total, unlike the effects of on-land earthquakes.  In their case, single-storey dwellings that are little more than wood and grass structures cause less deaths than in areas with multi-storey dwellings made of stone or concrete, and the effects are localised.

The US National Oceanographic and Atmospheric Administration (NOAA) is responsible for tsunamis warnings for the eastern Pacific (http://wcatwc.gov/), which are issued in the same way as extreme weather warnings.  Other organisations maintain a permanent watch and warning service for the entire Pacific basin, which is surrounded by the majority of the world’s large earthquake zones, mainly connected to subduction, and is the most prone to tsunamis.  Using bathymetry and landmasses, it is possible to model in detail the wavefronts of tsunamis and their travel times for any circum-Pacific earthquake.  So adequate warning is possible for most coastal areas following a major earthquake.  The Indian Ocean has only one major, tectonically dangerous plate margin, where the Indian Plate drives beneath Eurasia to form the Sunda Trench off the Indonesian archipelago.  Although discussed as recently as mid-2004, no tsunami-warning service is in place for the Indian Ocean.  One reason given for this lack of foresight is that the north-western part of the Sunda Arc has had little major seismicity for more than 150 years.  Therein lay the danger; subduction was locked and a major earthquake grew more likely the longer the quiescence lasted.   All the world’s seismic observatories recorded the massive disturbance and the exact location of the Sumatran event within minutes of its occurrence, but no warnings were issued.  The tsunamis arrived in Sri Lanka and India over 4 hours later, though within less than half an hour in Thailand and Sumatra, which were most devastated.  For the millions whose lives have ended or are in ruins, the greatest advance in the geosciences, plate tectonics, utterly failed them.

What is to be done?

Many geoscientists take pride (and a fair amount of public funding) in focusing their research on dangerous natural phenomena, supposedly aimed at giving warnings or mitigating their effects.   Take any natural calamity, whether it be earthquake or tsunami, volcanic eruption, mudslide, flood or even something so simple as helping provide clean water for the victims of drought or displacement by conflict.  Now list the lives saved by the direct efforts of geoscientists against the torrent of their publications and attendances at conferences.  Is there any cause for pride in the instrumentation, the theory and the field experience?  Or should we reflect on the hubris of scientific endeavour in the aftermath of such awful events?  Two days after the disaster struck I put together detailed topographic elevation data (from the Shuttle Radar Topography Mission – SRTM) for the coastlines that surround the Indian Ocean.  I had had them for 6 months, but did nothing except make some pretty maps for a conference presentation.  I had known what potential they have for predicting areas of flooding, and more important where refuges from inundation might be, but I found “better” things to do.  All coastal areas below 15 m elevation are at risk, and a great many correlate with the tsunamis’ worst effects.  What we could have done and what we did do generally emerge only in retrospect, and indulging in mea culpa serves no purpose.  Individuals have their own agendas, and they are rarely useful in any wider sphere.  The organisations that draw scientists together are not in themselves altruistic, but serve largely academic ends.  However, human tragedies surely remind us of a wider set of responsibilities, even if only momentarily.

A collective organisation of both knowledge and real needs, which sets aside career and the “advancement of science”, is probably the only means of putting the geosciences to work for fully human benefit.  For 40 years such a collective existed in the small form of the Association of Geoscientists for International Development (AGID), which aimed at knowledge transfer from its members to less fortunate areas.  For the latter half of its existence, AGID was subsidised by the Canadian International Development Agency.  A handful of members met at the 32nd International Geological Congress in Florence during late August 2004, the agenda being wholly about its survival or winding up following CIDA’s withdrawal of financial support.  The vote went for continuation.  But, despite helping some young geoscientists of the “Third World” make progress, AGID’s small size and limited aims and funding have proved unable to make it a force that matches real needs or the geosciences’ potential for assisting development.  Data and theory now present the opportunity to resolve two great challenges: giving every man, woman and child on the planet access to safe drinking water; and predicting and mitigating all natural hazards.  Every senior politician in the developed world pays lip service to both, each UN agency convenes to discuss them on a regular basis, and the International Union of Geological Sciences (IUGS) has proposed the International Year of Planet Earth (2005-2007) with those themes at the top of its agenda.  IGC-32, the largest ever gathering of geoscientists was dominated by humanitarian themes and the launch of the IUGS initiative. The International Year of Planet Earth was supposed to have been proposed by the Peoples’ Republic of China at the September 2004 UN General Assembly 59.  It does not appear on the UN web site, and the supporting web site www.esfs.org gives no news of its adoption. But there have been many “Years of…” and even several “Decades of…” from which we have yet to see any tangible outcomes, and little of the “awareness” that they are supposed to generate, certainly not in those areas of the world towards which they were directed.

One collective of professionals that has had a powerful impact on emergencies since 1971 is Médicins sans Frontières (www.msf.org), founded and administered independently of the world’s “great and good”.  Would a geosciences equivalent be feasible and supported?  Yet there are measures that even individuals can take.  At a UN Office for Outer Space Affairs meeting on the use of satellite data for mitigating disasters (Munich, 18-21 October 2004) www.zki.caf.dlr.de/events/2004/unoosa_workshop/unoosa_programme_en.html – Margaret Andrews Deller of the UK Open University presented her ideas (see link at the above web site) on a simple and low-cost way to reduce the impact of natural disasters.  Briefly, she based her suggestions on indigenous people’s deep knowledge of their surroundings.  Recognising that, it should be possible to provide communities with graphic images that highlight potential threats, in forms that are low-cost and easily understood by anyone, such as the use of images that incorporate perspective and show features in near-natural colours.  Her most important point is that such information would not be just a warning, but a means of showing people their homeland in a way that they can learn from and value. That would bring together those affected with those who come to their aid, should catastrophe strike, and would empower local people to take charge of their lives instead of being victims.

Easily understood information and advice is vital for potential victims of catastrophes, and a quick search of the internet reveals lots on all manner of hazards and how to avoid them.  NOAA’s tsunamis website http://wcatwc.gov/ is an excellent example.  Such information needs to be recast into forms that people outside the “information society” can easily understand, and to be distributed – not such a massive task.  What drew children to south Asian beaches on Boxing Day, the massive withdrawal of the sea, is the first sign of a tsunami.  On Pacific islands everyone knows what threat such a weird occurrence signifies, but nobody on the rim of the Indian Ocean did.  But isn’t it also essential for geoscientists to donate some of their publicly and industrially funded time to share their expertise directly with those so much less fortunate than ourselves?  Without that, our claim to be resolving humanity’s problems is a transparent sham.

Another large igneous province implicated in mass extinction

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At the end of the Triassic Period, around 200 Ma ago, life underwent a major crisis that so far has not been believably connected to either extraterrestrial or geological causes.  Previous studies have shown that the mass extinction was accompanied by an decrease in 13C in sediments that suggests a short-lived global warming of  between 2-4 °C at the Tr-J boundary.  That CO2 levels rose is suggested by a decrease in the density of pores (stomata) on fossil leaves.  It has been suspected for some time that the largest known continental igneous event, which accompanied early rifting of the modern Atlantic Ocean basin may have been responsible, but so far the dating of this Central Atlantic magmatic province (CAMP) has not been tied to the boundary conclusively.  A large consortium of Italian, French, US, Moroccan and Swiss has addressed the sedimentary and igneous record around Tr-J times in the High Atlas of Morocco (Marzoli, A and 14 others 2004.  Synchrony of the Central Atlantic magmatic province and the Triassic-Jurassic boundary climatic and biotic crisis.  Geology, v. 32, p. 973-976).  There, one of the few uneroded continental flood basalt sequences of CAMP (most preserved CAMP magmas are in the form of sills and dykes in offshore basins) occurs among Triassic and Jurassic sediments.  Their base deforms the underlying sediments, suggesting that eruption was onto unlithified sediments, shortly after their deposition.  Fossils from the sediments are of little help in tying down the age of eruption, however, Ar-Ar ages of the lavas are all within error of 200 Ma, and tally with magnetic stratigraphy from the Tr-J boundary elsewhere.  Both age and geochemistry of the flows are remarkably similar to those of flood basalts from the other side of the Atlantic.  Magmatic duration, like that in other large igneous provinces was of short duration, no more than a couple of million years.  So it now seems that three of the “big five” mass extinctions (the others are end-Permian, connected with the Siberian Traps, and the K-T boundary and associated Deccan Traps) have at least a partial cause from CO2 release by massive volcanism.

Iron isotopes enter the Archaean life debate

Some years ago geochemists obtained carbon-isotope data from 3.8 Ga rocks in Greenland that seemed at the time to be persuasive evidence for the emergence of life during or shortly after Earth’s most traumatic period.  Up to 3.8 Ga the Moon was bombarded by huge projectiles, and its companion Earth would have received at least 13 times the flux of destruction.  The carbon was within sturdy apatite grains from supposed iron-rich metasediments, and may have been preserved from later high-grade metamorphism.  Doubt has been cast on that hypothesis, either because of the unlikelihood of any carbon remaining unfractionated by heating, or because some aspects of the rocks’ geochemistry suggested that they we of igneous origin rather than sediments.  Readers will have seen in previous years’ EPN that a controversy rages over even tangible signs that suggest cellular material from rocks half a billion years younger.  Geochemists from France and the US have taken a different tack with the ancient Greenlandic rocks that ought to at least resolve the igneous versus sedimentary origin of the banded iron-rich rocks (Dauphas, N. et al. 2004.  Clues from Fe isotope variations on the origin of Early Archean BIFs from Greenland.  Science, v. 306, p. 2077-2080).  They found that the heavy iron isotope 57Fe is more enriched in the ironstones than in any igneous rocks, with little chance that the difference was induced by thermal fractionation.  They are metasediments.  But therein lies a surprise.  The heavy-iron signatures are greater than in less aged banded ironstones.  One way in which that could have arisen is from biogenic precipitation of soluble reduced Fe-2, perhaps involving anoxygenic photosynthesisers – because of the strong capacity of photosynthesis for setting electrons in motion, all such organic reactions create local oxidising conditions, whether or not oxygen itself is produced.

Torrid times in the Cretaceous Arctic

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Despite its latitude (above the Arctic Circle) the sedimentary depocentre of northern Alaska is becoming famous for its Cretaceous terrestrial flora and fauna.  Plant remains indicate luxuriant vegetation cover, and high excitement greeted the discovery of 8 species of dinosaurs (4 herbivores and 4 theropod predators (Fiorillo, A.R. 2004.  The dinosaurs of Arctic Alaska.  Scientific American, v. 291(6), p. 60-67).  How dinosaurs were able to survive the darkness of the Arctic winter is a bit of a mystery, unless the migrated as do modern caribou – Fiorillo cites evidence for small juveniles that would have been unlikely to have migrated far, because compared with adults they were much smaller than young caribou.  There would have been sufficient winter biomass for survival during the Cretaceous, but seeing and being active as cold-blooded reptiles pose problems.  At least one of the species had unusually large eyes, so one of the conditions for dinosaur’s remaining year-round seems established.  New data regarding climatic conditions in the far north have turned up after an most unusual and intrepid programme of drilling through a drifting island of pack ice over the Arctic Ocean’s Alpha Ridge, not far short of the geographic North Pole.  An extraordinary feature of the programme is that it took place between 1963-74, the core having only been examined in detail in the last year (Jenkyns, H.C. et al. 2004.  High temperatures in the Late Cretaceous Arctic Ocean.  Nature, v. 432, p. 888-892).  The Late Cretaceous part of the cores is black mud rich in terrestrial vegetation remains and marine diatoms, and totally lacking in evidence for dropstones and other debris from floating ice shelves.  Unfortunately, the Arctic sediments lack carbonate-shelled plankton remains,  so the now standard method of sea-surface temperature measurement is not possible.  However, Jenkyns et al. were able to use a method based on the fatty acids that survive in plankton membranes, results from which match oxygen-isotope palaeo-temperature measurements in Cretaceous cores from lower latitudes.  Astonishingly, even at polar latitudes, the Cretaceous Arctic Ocean seems to have been as warm as 15°C.  Climate modelling based on lower latitude data and estimates of CO2 concentration in the Late Cretaceous atmosphere falls around 10° short of these levels.  The conventional modelling requires 3 to 6 times more “greenhouse” warming than generally accepted, to account for Arctic sea temperatures in which we could swim in moderate comfort.  Possibly the modelling is awry.  One of the most important features of Late Cretaceous palaeogeography was a major seaway across North America that connected the Arctic with tropical latitudes.  It existed because global sea level was far higher than now, probably due to the oceans’ volume having been substantially reduced by huge magmatic outpourings on the floor of the West Pacific basin (the Ontong-Java Plateau), earlier in Cretaceous times, together with higher rates of sea-floor spreading.  The seaway would have been shallow, and thereby easily warmed.  Had poleward currents been possible in it, their flow would have acted very like the modern Gulf Stream to warm high latitudes.  Despite palaeoclimatologists reliance on models of heat circulation, it needs to be remembered that they are based on grossly simplified geographic features.  If they get it very wrong indeed for the well-studied Cretaceous, that casts doubts on climate modelling’s predictive powers for the course of current climate evolution.

See also: Poulsen, C.J. 2004.  A balmy Arctic.  Nature, v. 432, p. 814-815

An electronic antidote to eclecticism

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It is a plain to me as to any reader that EPN  is eclectic, and in some cases pretty impressionist; how else to write a monthly weblog about the broad spectrum of geoscientific developments?  So it is good to see websites with a much narrower focus, yet that manage to inform entertainingly and provocatively.  Such a site is www.mantleplumes.org, organised by Gillian Foulger of Durham University, currently a visiting scientist with the Volcano Hazards Team at USGS, Menlo Park, USA.  It covers the whole of “plumeology”; the tectonics, the magmatism, ages and wider features, even ideas about the presence or absence of plume-related features on other planets.  It has some powerful contributing essayists, such as Don Anderson and Warren Hamilton, who are not averse to scepticism and critiques, and represent work in progress on a book, Plates, Plumes & Paradigms just submitted to the Geological Society of America – a rare event to see preprints of book chapters.  It serves an educational role as well, with well-illustrated and up-to-date reviews of the mechanisms involved in large-igneous provinces., and thumbnails on a continent-by continent basis. Jason Morgan came up with the “hot-spot” idea about 33 years ago and launched a revolutionising force in plate tectonics.  It is good to see that there is still a vibrancy about the topic.

Ancient art

The hallmark of modern human’s abilities is the art left behind by our ancestors since about 30-40 thousand years ago.  Among the most enigmatic are those by Australian native people, that might date back as far as 50 ka.  The first were discovered by Joseph Bradshaw and his brother in the Kimberly Ranges of northern Western Australia in 1891.  The Geneva-based Bradshaw Foundation (http://www.bradshawfoundation.com/) is developing a comprehensive archive of rock-art images from across the globe, which will uplift anyone who visits it.

Bacterial reduction of arsenic contamination

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Following the tragic discovery ten years ago that tens of millions of Bangladeshis drink groundwater that is naturally contaminated by arsenic, the lessons learnt there have been applied on a global scale.  That has resulted in further cases with similar causes coming to light.  Remediation is chemically quite simple, and since the US reduced the maximum permissible arsenic level in public water supplies from 50 to 10 parts per billion in 2001 research into methods of removal have increased rapidly.  There are a number of methods that are based on adsorption of arsenic by iron and aluminium hydroxides and are low-cost.  But it seems that biological activity in aquifers can be equally effective (Kirk, M.F. et al. 2004.  Bacterial sulphate reduction limits natural arsenic contamination in groundwater.  Geology, v. 32, p. 953-956).  In the anaerobic conditions that favour the dissolution of iron hydroxide, which is often the most important source of arsenic in sediments, the conditions are also suitable for chemotrophic bacteria.  Among these are species that obtain metabolic energy from the reduction of sulphate ions to sulphide.  Where metal ions are also present, they combine with the sulphur to precipitate sulphide minerals.  In turn, sulphides readily accept arsenic from solution, thereby helping decontaminate potentially dangerous groundwater.  Arsenic-bearing groundwater is also found to have high methane levels, which suggests that methanogenic bacteria dominate its micro-ecosystem when sulphate ions are at low concentrations.  Perhaps it will prove possible to encourage sulphate-reducers to thrive in such waters, by the addition of some sulphate by injection.  That would a cheap remedy to what seems to be a growing risk in areas that extract groundwater from aquifers that are full of organic matter that creates the oxygen-free conditions that release arsenic into solution.

Bacteria in groundwater seem to have another benefit.  Where landfill contaminates subsurface waters with a cocktail of pollutants, the nutrients encourage bacterial colonisation, often in the form of biofilms in pore spaces.  It seems that their metabolism generates electrical currents (Gosline, A. 2004.  Bug “batteries” send out pollution alert.  New Scientist !8 December 2004, p. 17).  These create electrical potentials of several hundred millivolts that are easily detected by passive electrical monitoring.  The voltage highs occur at the margins of pollutant plumes in the groundwater, and can therefore be used to monitor spread of contamination and to indicate safe supplies.

Jared Diamond on the Flores “hobbits”

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Jared Diamond is a behavioural scientist who specialises in birds of east Asia and the Pacific, but he has made a major contribution to the popularisation of anthropology through his books The Third Chimpanzee and Guns, Germs and Steel.  His vast knowledge of the west Pacific makes him an able commentator on the amazing find of tiny people on the island of Flores (see: The little people of Flores, Indonesia in November 2004 issue of EPN).  He writes of the sheer diversity of opportunities for colonisation of the archipelagos that separate New Guinea from mainland Asia by Homo erectus, who populated the Far East for around 1.8 Ma (Diamond, J.  2004.  The astonishing micropygmies.  Science, v. 306, p. 2047-2048).  There has been speculation that Homo floresiensis became so small in response to a limited biological productivity on Flores, but Diamond is not at all sure – the Indonesian island chain has luxuriant flora and fauna compared with the Asian mainland.  But islands have limits to any population. Homo floresiensis probably arrived as a tiny group that flourished because of negligible competition.  Soon reaching the limits of support by the island ecosystem, full-sized colonisers with a limited gene pool would either die out or quickly generate smaller offspring, larger numbers of which could be sustained and reproduce.  Another of Diamond’s insights concerns the matter of similar populations on the many equally attractive islands in the chain.  If there were, that would imply easy island hopping, and therefore no reason for miniaturisation through evolution.  Modern humans have done just that, on the scale of the entire Pacific basin over the last 45 thousand years with no sign of evolving as dwarfed island populations – they had boats. Homo floresiensis’ ancestors almost certainly did not.  They could have swum the short distances between the islands at times of low sea-level, indeed they could have seen one island in the chain from the next.  In the case of New Guinea, had they reached the nearest island to it in modern Indonesia, they could never have seen it in the distance.  Diamond’s greatest surprise is how the micropygmies survived later fully human colonisation from 50 to 18 thousand years, when large people would have colonised the entire chain with ease, before proceeding to Australasia and Oceania.  Perhaps they coexisted through having a complementary food economy, as do modern African and Philippino pygmies, by some form of trade.  They may even have been too dangerous to hunt or attack.  Intellectually attractive as Homo floresiensis might be to us, steeped in Tolkienesque lore, Diamond cuts out the fantasy – they were so unhuman as to make the possibility of their disappearance through interbreeding highly unlikely.  Like chimpanzees, they would not only have been unappealing but possibly too unpredictable and strong for cross-species sex to have crossed the minds of fully human colonisers.

Mars in Science and Nature

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A year on from the landings of US Mars Rovers, Science devotes much of its early December 2004 issue to findings from the more revealing of the two missions, Opportunity (multi-authored 2004. Opportunity runneth over.  Science, v. 306, p. 1697-1756).  The articles are highly detailed accounts of the main finding from the various instruments aboard Opportunity, including the evidence for the activity of acid waters on the ancient Martian surface.  Equally interesting and considerably more graphic are important findings about volcanic and glacial activity in much more recent times, that come from the European Space Agency’s Mars Express Orbiter and the High Resolution Stereo Camera carried by it (Neukum, G and 42 others 2004.  Recent and episodic volcanic and glacial activity on Mars revealed by the High Resolution Stereo Camera.  Nature, v. 432, p. 971-979). Recently, excitement about evidence for living organisms on Mars rose with the discovery of significant amounts of methane in the Martian atmosphere.  Methane is likely to have a short life span (around 300 years) in the atmospheres of rocky planets.  There are two possible sources: methane-generating bacteria or release from volcanoes.  The High Resolution Stereo Camera shows conclusively that volcanoes were active on Mars until at least 5 Ma, when previously the planet was thought to be magmatically dead.  If fumarole activity continues, that could explain the traces of methane.

Tying down the Devonian-Carboniferous boundary

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Getting the stratigraphic column properly calibrated from relative to absolute time is all the rage these days (New benchmarks for geological time in EPN June 2004).  On the recent stratigraphic chart published in late 2003 by the International Commission on Stratigraphy, the Devonian-Carboniferous boundary has a “golden spike” global standard section and point (GSSP) dated at 359.2 ± 2.5 Ma.  Already, that is disputed because of new radiometric dating from an “auxiliary” global stratotype section (Trapp, E. et al. 2004.  Numerical calibration of the Devonian-Carboniferous boundary: Two new U-Pb isotope dilution-thermal ionization mass spectrometry single-zircon ages from Hasselbachtal (Sauerland, Germany).  Geology, v. 32, p. 857-860).  As well as holding the record for length of any publication title yet covered by EPN, the paper contains some intriguing points.  That a carefully determined age for the strata at Hasselbachtal has been possible is thanks to about six, centimetre-thick ash beds in richly fossiliferous sediments just above the faunally determined boundary.  Twenty-three single-zircon ages from the two ashes just above the accepted faunal boundary give ages of 360.5 ± 0.8 and 360.2 ± 0.7 Ma.  Now, to you and I and many less pernickety geochronologists, that spells out the well-known phrase or saying, “within error”, as indeed is that of the GSSP.  And, for a convoluted reason based on plotting an age from another tuff with these ages against the palaeontological data, the age presented for D-C itself is 360.7 ± 0.7 Ma.  This may be a better age than that of the GSSP.  But, so what?  The D-C boundary is not associated with any family-crushing catastrophe like the P-T or K-T boundaries, nor even that within the Late Devonian itself.  Are “they” going to move the GSSP from its present location in southern France, ratified in 1990, along with the vast pyramid of precious and intricately carved crystal, which no doubts marks its spot?  An altogether more serious threat to the established order is the stealthy attempt to abolish the last remnant of the great stratigraphic divisions inspired by Giovanni Arduino’s work in the 18th century; the Quaternary is besieged!  One of my spies, not unconnected with this episode of our own emergence on the planet, attended a stormy meeting at the 32nd International Geological Congress in Florence in August 2004, which seemed likely to expunge the Quaternary from the minds of all future geologists.  He gleefully reported that a mighty rearguard action had put off that evil day, at least for a while.  Sadly, the writing is already on the great IUGS/ICS stratigraphic wall chart – its is no longer there!  The last relic in officialdom is in the latest definitive publication (Gradstein, F.M. et al. 2004.  A new geologic time scale with special reference to Precambrian and Neogene.  Episodes, v. 27, p. 83-100).  On page 86, at the very top of the table conferring status on GSSPs, it is written “This composite epoch [the “Quaternary”] is not a formal unit in the chronostratigraphic hierarchy”.  So there you have it; the issue is getting things into proportion.

A record of the Palaeoproterozoic lunar cycle

One of the many natural processes that produce rhythmic sediments is the ebb and flow of the tide, twice a day and with an amplitude that peaks and falls twice each lunar month (today a 28-day cycle) to produce spring (new and full moon) and neap tides (the two half moons).  Tidal rythmites consist of thin laminae whose thicknesses vary regularly for many cycles.  Their occurrence dates back to 3.2 Ga, and along with other sedimentary structures formed by tidal action, such as “herring-bone” cross stratification formed by reversals in tidal currents, prove the presence of the Moon in orbit around the Earth.  Fine rythmites can be analysed to work out the length of the lunar month in the past, and help refine ideas on the evolution of the Earth-Moon system.  Rajat Mazumder of Asutosh College, Kolkata, India has analysed the earliest known tidal rythmites from the Palaeoproterozoic of NE India (Mazumder, R. 2004.  Implications of lunar orbital periodicity from the Chaibasa tidal rhythmite (India) of late Paleoproterozoic age.  Geology, v. 32, p. 841-844).  His work shows that between 2.1 to 1.6 Ga the lunar month was 32-days long.  Remarkably, the record in these sediments is as detailed as found in modern ones from estuarine silts.  As well as rhythms, they record occasional perturbations due to storms.  Using the changes in the lunar month during the last 450 Ma erroneously suggests that the system emerged from a period around 1.5 to 2.0 Ga following a major collision – that of course is ruled out by a total lack of evidence of such a catastrophe.  The new datum suggests instead a steady decrease in the lunar month, that corresponds with the Moon’s gradually receding from the Earth.  Energy apparently lost by tidal action is conserved by an increase in the angular momentum of the Earth-Moon system, and that forces the Moon ever further from us – its orbital velocity increases.

Update on the “Snowball”

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Two recent papers add weight to the “against” view expressed in For and against “Snowball Earth in EPN of October 2004”  One gives age of 709±5 Ma for tuff immediately beneath a supposed Sturtian diamictite from the western USA (Fanning, C.M & Link, P.K. 2004.  U-Pb SHRIMP ages of Neoproterozoic (Sturtian) glaciogenic Pocatello Formation, southeastern Idaho.  Geology, v. 32, p. 881-884), which does not tally with the radiometric age (685 Ma) of similar rocks not far away.  The other (Calver, C.R. et al. 2004.  U-Pb zircon age constraints on late Neoproterozoic glaciation in Tasmania. Geology, v. 32, p. 893-896), gives a 575±3 Ma age for sills intruding a “Marinoan” diamictite in Tasmana, and 582±4 Ma for a rhyodacite immediately beneath it.  This suggests that these antipodean glaciogenic rocks are correlative with those in Newfoundland and Norway, that are supposedly representatives of the Varangerian glacial epoch.  Yet the authors are pains to state that the Marinoan and the Varangerian are one and the same.  Read these papers if you are still confused!

The boys on the black stuff

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Tectonic activity continually re-paves the oceanic part of the Earth, though not in the manner of the awesome night-time machines seen frequently by owlish drivers as they negotiate the contraflows and cones on highways, large and small.  Slab-pull helps ease plates apart, forcing asthenospheric mantle to rise and partially melt as pressure falls off.  Or, at least that is widely believed, for active mid-ocean processes can only be observed at second-hand through samples scraped from the exposed ridge surface for analysis.  What once lay at the guts of spreading centres emerges only when slabs of ocean lithosphere slide nicely over continental margins because of compressive forces related to plate subduction.  Gravity demands that such obduction is a rare and special process, since oceanic lithosphere is denser than that of continents.  Indeed, as ocean floor ages and cools it become increasingly likely to founder into the deep mantle.  Ophiolites represent oddly buoyant parts of the ocean floor, almost certainly because they were once thermally anomalous or quite young at the time of their emplacement.  There is no guarantee that they represent run-of-the-mill oceanic lithosphere.  However, structures in them, especially a subsurface layer made of innumerable basaltic dykes and little else, show concretely that magmatism was dominated by continual extension; exactly as expected for a former spreading centre.  The most studied ophiolite is that of the Semail Mountains in Oman, which exhibits every definitive layer of lithosphere that point to magmatism in an extensional oceanic environment.  The crustal part is not the best guide to the ophiolite’s genesis, because melt chemistry varies so much with pernickety vagaries of melting and fractionation.  It is the mantle sequence that reveals what went on (Le Mée, L. et al. 2004.  Mantle segmentation along the Oman ophiolite fossil mid-ocean ridge.  Nature, v. 432, p. 167-172).  Laurent Le Mée and colleagues from the University of Nantes focus on chemistry and mineralogy of the well-preserved ultramafic rocks in the Oman ophiolite’s mantle layers.  Their results show how a whole number of petrogenetically important chemical features vary systematically parallel to the original axis of spreading, to define three distinct axial segments.  Within each are other regular fluctuations that define segments of lesser magnitude.  This along-axis chemical variability can be modelled in terms of large variations in the degree of mantle melting (between 10-30%), with the lowest degree coinciding with the major segment boundaries.  Those discontinuities also tally with increased numbers of mantle-cutting dykes (not the crustal sheeted dykes).  Major segments probably formed from regional upwellings of asthenosphere, whereas those with shorter wavelengths reflect individual diapirs.  Along active spreading centres, segmentation of chemical affinities in basalt lavas seems to link with various magnitudes of transform faulting, and it is this local tectonics that shows up so nicely in the Oman mantle sample.

Archaeology and fluorine poisoning

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In 1783, the Icelandic fissure volcano Laki erupted.  One in five Icelanders perished, partly because most of their livestock died in the eruption’s aftermath, but also because of direct effects from the geochemistry of the lava.  The effects spread to much of continental Europe, but with less gruesome results.  There are many archival reports of the presence of a bluish-grey haze or “dry fog” and an acrid smell to the air – probably high sulphur dioxide levels.  There was an increase in mortality in Europe too, with 25 % more deaths over and above the annual norm in France, possibly exacerbated by the fog’s coincidence with a scorching summer.  The politician-scientist Benjamin Franklin was the first to make the connection between news of the eruption, atmospheric oddities and spectacular sunsets.  The spread of volcanic emissions far and wide at the surface can be put down to the relatively quiet effusion of lava from Laki; explosive eruptions generally jet gases and ash upwards to reach the stratosphere.  The principal killing agent was the fluorine-rich nature of the gas and ash from Laki, which induced a rapid onset of bone-diseases in humans and livestock alike.  That is something special to Icelandic magmatism, the only significant above-sea level part of a mid-ocean ridge system.  However, fluorine compounds commonly occur in some volcanic ashes, and mortality spread beyond the immediate effects of volcanism is a major threat.  Currently, archaeologists and pathologists are exhuming burials from the time of Laki’s last known killer eruption to seek statistics on the influence of fluorosis in its human victims (Stone, R.  2004.  Iceland’s doomsday scenario?  Science, v. 306, p. 1278-1281).  The signs are bony nodules and spiky fibres that fluorine ingestion, most disastrously from water, produces.  Early results reveal many skeletons with clear malformation.  Fluorosis leads to a hugely painful and lingering death.  Usually it results from a slow build-up of fluorine from contaminated water in areas that are rarely associated with active volcanism.  The clearest sign of its onset is a brownish mottling of children’s teeth, and it is easily remedied by changing the water supply.  Delivered massively and suddenly, as it was in late 18th century Iceland, gave little chance to its victims.  A recurrence would possible be just as disastrous today.

Neanderthals vs moderns: how come we won?

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One of the great paradoxes in palaeoanthropology is how modern humans in Europe survived the last glacial maximum whereas Neanderthals did not.  In fact they became extinct some 10 thousand years before conditions reached their coldest.  The paradox lies in the fact that Neanderthals were superbly adapted physiologically and behaviourally to life in cold, harsh conditions, having lived through the previous glacial period since at least 200 ka ago.  Modern humans evolved, since first appearing around 160 ka, by adapting to conditions in Africa – an environment far different from that of Europe in every conceivable way – and bands migrated outwards, probably because of growing aridity as global climate cooled.  Their future was akin to that of Africans from modern Kenya, should they decide to migrate to Arctic Canada.  Quite probably Kenyans would survive, because the Innuit are supremely generous and friendly people.  They have to be in order to have survived their chosen environment.  It is this paradox that concerns archaeologist Paul Mellars of Cambridge University (Mellars, P. 2004.  Neanderthals and the modern human colonization of Europe.  Nature, v. 432, p. 461-465).  Genetic evidence from recovered Neanderthal DNA shows conclusively that the two occupying groups in Europe did not interbreed to any significant extent, so the paradox can therefore not be resolved by complete hybridisation.  To what extent were modern humans better equipped with tools than were Neanderthals?  The archaeological record shows that from about 40 to 35 ka there was a burst of cultural advance among moderns, that spanned the Middle East to the Atlantic shores of Spain – the Aurignacian technology.  It coincided with an equally explosive spread of aesthetic culture, involving such symbolism as to be widely considered as a mark of sophisticated language and communication, perhaps a sign of an advance in brain structure that Neanderthals did not experience.  One of the big surprises in recent archaeology of this crucial period was that modern human remains associated with early Aurignacian artefacts turned out to be burials later than the tools were discarded.  To some, this left open the possibility that the technological advance may have been achieved by earlier occupants – the Neanderthals themselves.  Indeed there are signs that these original Europeans did make cultural advances around that time, in the form of the Chatelperronian artefacts.  Mellars points out that moderns of the time did not bury their dead near habitations, whereas Neanderthals made a habit of it, so the inference of especially smart Neanderthals is probably unfounded.  There are two geographic patterns associated with the Aurignacian, one arcing through Central Europe to France, the other along the Mediterranean coast, each showing distinct differences in technology.  This is regarded as support for two populations of colonising moderns.  The Chatelperronian is now regarded as one of many signs of some kind of cultural transfer between Neanderthals and moderns, and therefore of regular contact.  Whatever those contacts involved is unknown, but immaterial as regards the fate of the Neanderthals.  They disappeared without a trace, by 30 ka at the latest.  Mellars’ review concludes with the view that this extinction was a matter of outcompetition, as conditions were steadily deteriorating towards the last glacial maximum.  It could well be that moderns, faced by the perils of a move to harsher conditions that were oscillating rapidly due to Dansgaard-Oeschger events, were forced to adapt or perish.  The Neanderthals did not, or they did it too late.  Their culture had served them well, and why should they have changed it?

A discovery that will run and run?

Do you know why humans have prominent buttocks (the ape has none worth a sidelong glance)?  I thought not; most people do not wish to know.  Here is how to find out.  Begin to walk, preferably in secluded woodland.  Now clutch each “cheek”, one in either hand.  Do you notice anything?  No, the gluteus muscles do nothing, apart from wobble a bit.  Now, if this is possible, begin to lope along the path, still with a buttock in each hand.  There, they work!  Hominids are not just striding bipedalists, but evolved to run: not so fast as to collapse after a hundred metres, but kilometre after kilometre at a relentless lope.  This is the conclusion from anatomical and bio-mechanical study of hominid remains, going back to our oldest undisputed ancestors (Bramble, D.M. & Lieberman, D.E. 2004.  Endurance running and the evolution of Homo.  Nature, v.  432, p. 345-352).  The outcome is that modern humans, and probably every earlier species of Homo, can and did run any other animal to exhaustion.  The australopithecines probably could run down a hedgehog, but not prime meat.  The study goes further, since there is more to running than leaning forward and putting a leg out to stop us falling on our faces.  The arms are involved, and flexure of the waist.  Mechanically, a higher waist and shorter arms are more effective aids to running, as of course are proportionately long legs.  The technical arguments in this hypothesis are somewhat unfamiliar, except to the sports scientist, but one immediate conclusion is easy.  No modern hunter-gatherer really likes to run a marathon each day, even though they could, and would much rather sit and watch the world go by, so long as he or she is fed.  Unless the utter pointlessness of prolonged physical activity, other than a means of sustenance, becomes a cultural necessity for other reasons, the next stage in human evolution may well see the buttocks atrophy.  Legs will shorten, the waist drop and the arms lengthen, once more, to help us knuckle-walk up to the chip shop.  There may only be one way to preserve the buttocks; to encourage wolf packs in city parks.

Something to chew over

Much of the human evolutionary story depends on the most enduring of fossil material – teeth.  So, dentists have been drawn increasingly in palaeoanthropology.  Since species are defined as whole organisms, the use of such tiny fragments as teeth should be worrying.  But they are often the only material, and specialists in dentition have convinced themselves that teeth “work” as phylogenetic indicators.  But there are always dental variations between individuals, and therefore a danger of doing something akin to cheating with a jigsaw puzzle; forcing misfits into the cussed blue sky part in order to get on.  Recent research on the genetics that underlie the development of mouse teeth (Kangas, A.T. et al. 2004.  Nonindependence of mammalian dental characters.  Nature, v. 432, p. 211-214) shows that different levels of a protein (ectodysplasin) affect the shape changes during development of dentition..  Ordinary mice have different molars, depending on tiny differences in the growth points of tooth crowns during dental development, and that depends on ectodysplasin levels.  Clearly, major differences among fossil teeth ought to point to adaptation (and speciation) to very different diets and ways of biting.  But now there is a devil in the detail of the teeth of mammals, although the authors do not extend their observations explicitly to those of hominins. Specialists in human speciation will probably rationalise away the possibility of something going awry with the hominin clade, and perhaps rightly so, if the implications of Kangas and colleagues work diffuse to their arena.  However, everyone is aware of the dramatic polymorphism of human mastication, from mouth-filling “tombstones” to a tiny pointiness that worries the experienced observer.

Grow your own bridge, hill or fortress

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From time to time, truly odd ideas emerge, even from such a conservative bunch as geoscientists.  They are often based on quite mundane science.  If you pour sulphuric acid on limestone, of course it fizzes violently because CO2 is a product of the simple reaction.  Less noticeable is that the other product, hydrated calcium sulphate or gypsum, is considerably less dense than the calcite in limestone.  The solid residue swells.  “What if….?”, thought Dutch geochemist Roelof Schuiling (Ravilious, K 2004.  The new stone age.  New Scientist, 20 November 2004, p. 38-41).  His idea was to put the simple phenomenon to practical use; infiltrate sulphuric acid into porous limestone and the swelling will bulge up the surface.  This does happen naturally, where sulphide-sulphate oxidising bacteria generate sulphuric acid, which renders limestone to an easily erodable mess, and in some soils generates gypsum lenses that bulge up the ground into surface blisters.  Schuiling reckons that the huge sulphuric acid surplus, created partly by removing sulphur from vehicle fuels, could be used as a kind of geo-engineering tool on a vast scale.  For instance, the coralline shallows beneath the shallow Palk Straits that separate India and Sri Lanka, could be induced to bulge up and create an island ridge, and so complete what is known as Adam’s Bridge that nearly links the two countries.  Closer to home, the Low Countries might become the “Slightly Higher Countries”.  Worryingly, the technology to make the process viable is simple, if a little expensive on the scales envisaged.  The worry, of course, is yet more CO­2 emission plus the effect on the environment of so much sulphate and a massive fall in pH.

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Three web sites that have been suggested are well worth browsing.  Bernie Gunn has assembled a monumental database of the geochemistry of volcanic rocks at http://www.geokem.com .  That, in itself,  is a magnificent resource for anyone working on the topic, but the site also has a comprehensive guide to good laboratory practice that will be invaluable to anyone beginning to work in the field., plus a host of good reference material and links.  Its quality is hardly surprising since Bernie has been engaged in geochemical research for more than 3 decades at the University of Montreal.  Another dimension to geological web resources is revealed by that compiled by Fettes College in Edinburgh at http://www.fettes.com/shetland .  It is an encyclopaedic source of environmental information on one of Britain’s many microcosms of Earth science.  It ranges from the Shetland Isles’ long geological evolution to its present geomorphology.  Fettes is a private school, with a glittering roll of alumni.  Equally encyclopaedic is http://paleodb.org , which is as near to a global database of palaeontology as you can get at present.  One of the highlights is being able to plot occurrences at the genus and species level on interactive maps, as well as browse and analyse the contents statistically.  Users do need to know how to spell taxonomic names!  Once you have compiled a map (the only trilobite whose name I can spell is Dalmanites!), you can zoom in.  If you click on an occurrence up comes a summary of the locality, with links to other parts of the database, including other fossils at the locality.  Wisely, location detail is crude enough to deter collectors from ravaging sites.  The database is compiled by 140 contributors in 11 countries.  This a site for specialists, but a beginner can learn a great deal from it.

A volcanic role in the origin of life?

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Studies of the organic chemicals in meteorites and in “space snow” that falls continually on the Earth, show that amino acids and nucleotides (the CGAT building blocks of nucleic acids), together with other moderately complex compounds, were widespread in the solar nebula as it formed.  They can form in the absence of life.  Life’s dependence on DNA and RNA for its necessary self-replication marks a chemically complex step that assembled such building blocks by a process of polymerisation.  That presupposes an awful lot of chance reactions, none more so than the formation of the peptide bond that dominates genetic material and proteins.  Lots of mechanisms have been tested, but none work sufficiently well in a test tube to be plausible candidates for processes on the early Earth.  Perhaps the simplest, first proposed more than 30 years ago is the operation of a simple gas called carbonyl sulphide (COS).  Experiments that expose amino acids to carbonyl sulphide in water at “room temperature” yield lots of peptides in a matter of a few minutes to hours (Leman, L. et al. 2004.  Carbonyl sulphide – mediated prebiotic formation of peptides.  Science, v. 306, p. 283-286).  The more metal ions, such as those of iron, lead and cadmium, that are in the solution, the more efficient the reactions.  The likeliest place for such processes to go on would be near submarine hydrothermal vents, as COH quickly breaks down once emerged from a volcanic source.  Its role could have been crucial in the complex molecular evolution that many biochemists believe to have been intimately associated with the structures of clays and sulphide minerals that hydrothermal activity produces in abundance.

Mineralogy links

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Information on mineralogy is often hard to find on the web, so the University of Wurzburg Institute of Mineralogy in Germany has created a comprehensive set of links that cover a wealth of topics.  They include teaching materials at different levels, information on experimental and analytical techniques, thermobarometry, mineral descriptions and crystallography, economic mineralogy, gemmology and much more besides.  Go to http://www.uni-wuerzburg.de/mineralogie/links.html

Linking seismic tomography to chemical mantle heterogeneity

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Analysis of historic, global seismograph records using sophisticated software allows far more than the detection of various discontinuities in the deep mantle and core that figure in most textbooks.  Essentially, it maps parts of the mantle where P and S waves travel faster or slower than expected from the depth.  Up to now, most results have been interpreted in simple terms of cold (fast) and hot (slow) patches, which have been linked to gross tectonic features such as signs of descending slabs far below the earthquake belts associated with subduction, and possible zones of rising mantle that might (or might not) be plumes.  That leaves a lot unsaid about the mantle, for rising and falling of material is linked to density, and that can be due to temperature anomalies, and also to compositional variations involving either bulk chemistry or different assemblages of minerals in mantle rock.  A difference in seismic wave speed can be an ambiguous indicator of possible motion.  Making the connections between wave speed, temperature and composition is an order of magnitude or more computationally taxing than the tomography itself, but it has been shown to be possible, given supercomputer power and plenty of free time (Trampert, J. et al. 2004.  Probabilistic tomographic maps chemical heterogeneities throughout the lower mantle.  Science, v. 306, p. 853-856).  Trampert and colleagues from the Netherlands and the US factored in mineral physics and temperature data, and were able to calculate the probabilities of tomographic features having a thermal or compositional origin.  Their results will worry some of the earlier workers on seismic tomography who used a simplistic connection with temperature and thus slow = hot = low density and rising, while fast = cool = high density and sinking.  Some zones of low wave speed can as well be connected with high-density mantle as with hot, buoyant material.  That plays havoc with concepts of plumes rising from the core-mantle boundary, that have been all the rage since moderately well resolving tomograms appeared.  Trampert et al’r results, which superficially look just the same as other tomographic renderings of the same seismic data, include statistical evaluations of the likelihoods of wave-speed shifts being either thermal or compositional in origin.  They reveal that many of the slow zones are probably chemical and mineralogical heterogeneities, especially in the deepest mantle levels.  One of the largest slow zones known rises obliquely from the core-mantle boundary around southern Africa towards the surface in NE Africa.  It was leapt on as a reputed superplume, perhaps connected to the last outpouring of flood basalts in Ethiopia and the Yemen around 30 Ma ago, and still active beneath the Afar Depression.  Chances are, from the new work, that it is denser than average and not especially hot.  Mantle geochemists will probably be gleeful at the new look at deep mantle, because they have long been wrangling ideas about gross lateral variations in the source chemistry of basaltic magmas.  Some enthusiastic geotectonic speculators might remain very silent, in the hope that the Dutch-US team’s work is not duplicated, and fades away…

See also:  van der Hilst, R.D. 2004.  Changing views on Earth’s deep mantle.  Science, v. 306, p. 817-818

Bedout end-Permian “impact” hammered

The claim that a large circular feature beneath the sea bed between Australia and New Guinea is linked to the end-Permian mass extinction (Becker, L. et al. 2004. Bedout: A possible end-Permian impact crater offshore of northwestern Australia.  Science Express 14 May 2004 – www.sciencexpress.org)  (See Crater linked to end-Permian extinction, June 2004 EPN) has met with a flurry of sceptical comment in letters to the editor of Science(2004, v. 306, p. 609-613).  Becker and colleagues have published several articles on the P-Tr boundary, including data on noble gases from the boundary in China, which are alleged to be consistent with an extraterrestrial influence, a meteorite from Antarctica which they consider to be a fragment of the impacting body and this year the claim for shocked minerals and impact glass in sedimentary core over the Bedout structure.  There have been unsuccessful attempts to duplicate the results on the noble gas analyses, the Antarctic meteorite is regarded as being insufficiently altered to be as old as 250 Ma, and as regards the Bedout material, the authors of the letters to Science consider none of the evidence to stand up to proper scrutiny.  One letter from specialists in the US, Russia, South Africa, Austria and the UK (Renne. P.R. and 7 others 2004.  Is Bedout an impact crater?  Take 2.  Science, v. 306, p. 610-611) also claims that the 250 Ma argon-isotope age for Bedout samples is misconceived and without objective basis.  One of the authors, Jay Melosh of the University of Arizona, is reported to have said that the Becker group, “..have deeply muddied the waters about what is going on at the Permian/Triassic boundary”.  These and material in the other letters are tough words indeed.  Becker’s group is funded by NASA, and when the flurry of letters hit home earlier in October, NASA sent a team of three scientists, including Becker, to resample the Chinese P-Tr boundary section.  Ten geochemistry laboratories will receive splits of the material to settle the issue of noble-gas evidence for an end-Permian impact.  But it looks very much as if a major scandal may break when the multi-lab analyses are published next year.  That is not to imply that there are no other skeletons lurking in cupboards along with impact-related materials.  A few years ago, editors of a major journal were asked to withdraw or refute a paper that used analyses of impact-related materials that had found there way to several laboratories without the permission of their originators or their names being mentioned.  The kudos associated with publishing on extraterrestrial influences on biological extinction patterns seems hard to resist…..

See also:  Dalton, R 2004.  Comet impact theory faces repeat analysis.  Nature, v. 431, p. 1027.

The little people of Flores, Indonesia

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At the end of October 2004 the front pages of newspapers world-wide carried a major geoscientific story; not about some natural disaster but the discovery of astonishingly tiny people who shared an island with us “big ‘uns” not so long ago.  They were not pygmies, but an entirely different hominin species from ours (Brown, P et al. 2004.  A new small-bodied hominin from the Late Pleistocene of Flores, Indonesia.  Nature, v. 431, p. 1055-1061; Morwood, M.J. et al. 2004.  Archaeology and age of a new hominin from Flores in eastern Indonesia.  Nature, v. 431, p. 1087-1091).  That the species came to light at all is down to the skill of Indonesian archaeologist Thomas Sutikna and his team of workers, who found the most important remains.  The bones had the consistency of putty, because the find was made in a cave in humid tropical rain forest and fossilisation had not begun.  By being treating with a glue, oddly known as “Tarzan’s Grip”  the remains survived excavation to be analysed in the lab.  About one third the size of a modern human’s, the skull was at first suspected to be that of an infant Homo sapiens.  Even cursory examination proved beyond doubt that it was not.  It carries worn adult molars, has no chin and possesses clear brow ridges.  Limb bones suggest a stature around 1 metre (by far the smallest member of the human family), with proportionately longer arms than ours.  Leaving aside the sheer tinyness of this roughly 20-year old female, these features most resemble Asian H. erectus, whose remains from mainland Asia and the larger Indonesian islands date from before 1.5 Ma to possibly as late as 20 ka. 

Dates from the whole suite of Homo floresiensis remains show a remarkably long occupation of Flores, certainly for most of the last glacial period until 18 ka, and perhaps extending back 840 thousand years and to as recent as the early Holocene.  For the later part of their occupancy members of H . floresiensis must have shared the densely forested island with modern people, who arrived there between 35 to 55 ka ago.  How the little people arrived is a problem.  Unlike the western Indonesian islands of Sumatra and Java, which would have been connected to Asia by land bridges during periods of glacial low sea levels, Flores and the eastern Indonesian chain of small islands are surrounded by water that is deeper than 200 metres.  Even the greatest extent of continental ice during the Pleistocene could not have drawn off enough sea water to create a dry passage from Java, and Flores is not adjacent to that known home of H. erectus, but separated from it by the islands of Sumbawa and Komodo, and more deep channels.  Together with the hominin remains in the cave are bones of the notorious Komodo Dragon, rats as big as dogs and minuscule elephants, so the original colonisers could have drifted from Java on floating vegetation rafts in the same way as the precursors of these other animals.  Unlike rats, monitor lizards and elephants, it is unlikely that they swam the necessary 150 km, and there are no records of pre-modern human boats.  Whatever, new arrivals on small islands find totally different conditions from those on larger ones or continents.  Potential food is limited, yet predators are fewer.  There is a well-known tendency for evolutionary miniaturisation of larger mammals, the tiny elephant Stegodon found in the same cave being a case in point.  In general it is reckoned that small-island mammals tend towards a size that is equivalent to a very large rabbit.  Not so for lizards, and the Komodo Dragon, still a terrifying predator on the eponymous island, would have been top of the food chain on Flores.

Another puzzling feature of H. floresiensis is that despite having brains the size of a grapefruit (roughly the size of those of australopithecines), they seem to have used both sophisticated tools and fire.  They were not dim-witted.  Their overlap with modern humans for so long is also intriguing.  In Europe the Neanderthals, physically more than a match for any modern human, drifted to extinction within about 5 thousand years after first encounters.  On Flores, the truly diminutive H. floresiensis clung on for far longer, possibly because resources were much richer than in frigid high latitudes.  Local people throughout eastern Indonesia today tell legends of the little people they call Ebo Go Go.  Perhaps they survived into far more recent times.  Undoubtedly, the dense forests and innumerable caves of the island chain may have other surprises in store.  For the moment, there can be none greater than finding that modern humans walked the Earth with at least two other human species not that long ago.  Nor is that of scientific interest alone.  As the editorial in New Scientist of 30 October 2004 observes, “…Homo floresiensis throws into doubt many of our assumptions about intelligence”.  They lived just as successfully as modern human colonisers of Flores for tens of thousands of years, despite the competition and possibly worse.  So brain size may not be the key to cleverness on which we pride ourselves.  Nor are we as unique as we generally suppose.  As with Tolkien’s hobbits, we should be humbled by their tenacity.

Anthropological nit picking

The chances of extracting human DNA from old bones to compare with that in modern populations are pretty slim.  It has been done for two Neanderthal specimens, and showed that living humans carry no sign of their involvement in producing hybrid offspring fit enough to pass genes upwards through the generations since about 35 ka ago.  Preservation of such molecular material requires extra-special conditions.  But there may be another way, which has a flavour of the opening sequences in Jurassic Park, where dinosaurs were cloned from blood preserved with their parasites in amber.  Body and hair lice are species-specific (we do get bitten by fleas from rabbits, cats and rats, but not by their lice), and the beasts prefer hosts who live cheek by jowl together.  Hair lice are especially good, because as any parent knows they leap as soon as kids get in a huddle, but no more than a few centimetres.  Comparing hair lice from modern humans and chimpanzees, Dale Clayton and David Reed of the University of Utah were able to show by comparing their mitochondrial DNA that the two species’ origins are about as old as the >5 Ma split between the human and chimp evolutionary clades.  Taking the method a step further to compare human head lice an astonishing feature emerged (Reed D.L. 2004. Genetic Analysis of Lice Supports Direct Contact between Modern and Archaic Humans. Public Library of Science:Biology v. 2, e340).  There are two genetically distinct groups in the species Pediculus humanus.  One has a global distribution and infests head and body hair, the other only being found in the Americas and is found exclusively on the scalp.  Their mtDNA molecular clocks suggest a divergence more than a million years ago.  Although they parasitise modern humans, they diverged before even archaic humans appeared on the scene.  The authors suggest that the divergence might have coincided with the separation of the two main populations of Homo erectus, an Africa one that evolved to modern humans and that in Asia, which probably was not on the human clade.  For one human species to carry two subgroups of anciently separated lice suggests that our ancestors went “head to head” with H. erectus, once in Africa and then perhaps much later in Asia, en route to the Americas.  The next step concerns considerably more intimate intra-species contact;  the team is going to investigate the different genus of human pubic lice…..  The collection process may well be underway as I write.

The perils of genealogy

With all kinds of public records on the web and others easily accessible from registry offices etc., tracing one’s ancestry has never been easier, should you be bitten by the family-tree bug.  Genealogy is addictive, out of a sense of adventure, a desire to “belong”, the possibility of tracking down untold riches because a maiden great-great aunt died intestate and her millions were invested in blue-chip stock to await your appearance at the trustees’ door, or because train-spotting has lost its frisson of excitement.  I suspect that there are times when “googling” is slow because genealogist are on line.  There is an old chestnut that if your researches successfully reach back far enough, you will find that William of Normandy or Eric Bloodaxe is a direct ancestor.  In fact research into human Y-chromosome DNA shows very clearly that Genghis Khan and his near relatives dominate the genes of millions of men in parts of Central Asia (see Darwinian evolution of humans challenged by Y-chromosome data? in EPN, March 2003).  That is  special case, as the eponymous warlord slaughtered most of the men in conquered areas and put most of the women into concubinage, and made damned sure that only he and his male kin had droit de seigneur, or its Mongol equivalent.  Simple arithmetic suggests that the chestnut holds true.  Going back generation by generation all of us have 2, 4, 8, 16, 32, and so on, direct ancestors.  The algorithm is simply 2n, where n is the number of generations.  Say a generation is 25 years, a millennium ago our ancestors would be 40 generations back.  Each of us would have had a trillion such great-great-great-great— grandparents on this simple basis, half men and half women.  Well, there would have to be 500 billion women, but maybe less men, if Genghis’ unwholesome habits were common.  Of course it is more complicated than that, because human populations are separated geographically, and in the past encounters would have been between relatively few travellers.  In fact, for some populations, such as those of pre-colonial Tasmania, contact had been cut off many millennia ago.  Because of the varied evidence for ancestors from whom all humans are genetically descended, such as “African Eve” (>150 ka) and “Big Daddy” (more recently), it is tempting to develop sophisticated models for genealogy (Rohde, D.L.T et al. 2004.  Modelling the recent common ancestry of all living humans.  Nature, v. 431, p. 562-566).  Leaving aside very isolated populations, such as the aboriginal Tasmans, the modelling suggests all of us only need to go back to about 3000 BC to find the ultimate tip of our family tree – our universal, identical ancestor. Anyone else who lived at that time sadly might seem to have had no effect whatever on our generation.  However, pedigree is not necessarily something that would justify you putting a coat of arms on your living room wall.  What we are genetically is not the same as suggested by our family tree.  Further up the tree, the less chance there is that someone appearing in it passed on any genes whatever to you or me.  The exponential law of genealogy no longer works, and the number of our genetic ancestors increases far more slowly.  A proper search for who in your past helped determine what you are requires DNA from everybody, and I don’t see many family-tree fanatics queuing to have their cheek cells swabbed, and nor will I.  I am quite happy that whomever passed on my patrilineal family name was probably one of William the Conqueror’s spear carriers in 1066.  The genealogy goes cold not many generations back, as, in my father’s words, “they were all probably illiterate anyway”!

See also:  Hein, J. 2004.  Pedigrees for all humanity.  Nature, v. 431, p. 518-519.