Category: Anthropology and Geoarchaeology

Chris Stringer and William Davies report on two recent conferences about the Neanderthals in the 25 October issue of Nature (Stringer, C. and Davies, W 2001.  Those elusive Neanderthals.  Nature, v. 413, p. 791-792).  Debate continues on what happened to them, and why.  Assimilation by gene flow remains a possibility with a few researchers, despite the mismatch between fragmental Neanderthal DNA and that from modern people, and the inability to get Cro-Magnon genetic material is vexing.  Acculturation – the influence of the behaviours of groups on one another – is also an unresolved issue.  At the centre of that particular debate are tools associated with late-Neanderthal sites that bear close resemblance to those of early Cro-Magnons; the so-called Châtelperronian.  The problem is precision and accuracy of dating the material, which, of course, constitute the palaeoanthroplogist’s Sword of Damocles.  Dating using the decay of ¹⁴C has long been a right old mess, what with variations in the cosmogenic productivity of the isotope, and the tendency of common bone samples to pick up stratigraphically younger carbon from humic acids in soils.  Charcoal is the material of choice, but in the case of Châtelperronian artefacts only associated bone seems to be available.  Help might be on the way in resolving inaccuracy that stems from variable ¹⁴C productivity by using marine-core data to calibrate terrestrial ¹⁴C dates to calendar years (the “CalPal” curve).  It does, however, seem to be peeking over the horizon at present.

One of the alternative processes that might have snuffed out Neanderthals is climate change.  High-resolution marine records are not too useful in that regard, because they reflect global processes, and Neanderthal demise was a regional issue.  Pollen records from lake sediments in Italy now reveal the intricacies of European climate during the critical period around 30 ka.  It was time of rapid fluctuations in tree cover.  However, similar rapid vegetation shifts occurred long before modern human influx, and the Neanderthals survived them.  One possibility, allied to the competitive-disadvantage hypothesis, is that Cro-Magnons brought a steppe culture with them, which allowed them to occupy open country more successfully than Neanderthals with a woodland culture.

The topic is stymied by imprecise dating (it can be as bad as ± 4 ka), so that open-season for speculation is protracted.  There is a reluctance to consider extinction through epidemic diseases brought by newcomers, and against which Neanderthals had no immunity.  Disease has played such a huge role in population crashes throughout recorded history, that for it not to be at the forefront is curious.  It is a widely supported hypothesis for extinction of large mammals that coincided with first entry by modern humans into the Americas ( see Late Pleistocene mass extinction – July 2001 Earth Pages).  That would have had to involve jumps between species, rather than simple transmission of killers such as measles between genetically very similar populations of humans.

En route out of Africa

Finds of H. erectus and artefacts in China and Georgia date back as long ago as 1.8 Ma; the earliest signs of massive diffusion of early humans protected by their culture from entirely new climates and surroundings.  The great question is, “Which way did they go?”  To many palaeoanthropologists, obstacles presented by the Arabian Desert and Caucasus Mountains, favoured exit from Africa via the Straits of Bab el Mandab (closed at that time) and coastal diffusion.  It now seems that movements of early humans did reach the Levant at a very early date.  Ron Hagai and Shaul Levi have produced strong evidence for H. erectus’ presence in the Dead Sea rift at around the same time (Hagai, R. and Levi, S.  2001.  When did hominids first leave Africa?: New high-resolution magnetostratigraphy from the Erk-el-Ahmar Formation, Israel.  Geology, v. 29, p. 887-890).  They found that sediments enclosing primitive, Oldowan tools (but no skeletal remains) accumulated during the period between two magnetic polarity reversals.  With other evidence, these correlate with the Olduvai subchron from 1.96 to 1.78 Ma.  Definitely a “first” for the Middle East, but by no means proof that this lay on the route to wider colonization, even at Dmanisi, across the Caucasus in Georgia.  Little would prevent easy diffusion from East Africa along the proto-Nile or the Red Sea coast to reach the Dead Sea rift, but the obstacles to the north and east of Israel would have been far greater for poorly clad and equipped Erects.

In a small temple on the south slopes of Mount Parnassus in Ancient Greece sits a somewhat befuddled lady, her inhibitions definitely down and she sometimes becomes delirious and thrashes around.  The great and the good seek her opinion on matters of state.  Perhaps for almost 2 millennia, successive pythia (pythia) of the Delphic Oracle had a steady passing trade.  Writers from the classic times of Greek and Rome leave little doubt that the pythia’s powers stemmed from three things: a fissure and a spring lying at the centre of what became revered as the Sanctuary of Apollo, and a vapour that emanated from her chamber.  The Oracle was seemingly a matter of geology and its mystique. 

Indeed there are two intersecting faults passing right beneath the Oracle.  Suitably encouraged, a team from Florida State and Weslyan Universities, and The University of Louisville, USA has been studying all aspects of the site since 1995 (de Boer, J.Z., Hale, J.R. and Chanton, J.  2001.  New evidence for the geological origins of the ancient Delphic oracle (Greece).  Geology, v. 29, p. 707-710).  Where others failed before them, they have discovered evidence for a spring and traces of hydrocarbon gas leaking from a bituminous limestone cut by the faults at depth.  One of the gases in the mixture is ethylene, once used as an anaesthetic, and known to cause just the symptoms in the pythia described in ancient accounts of her powers.

Seafaring Homo erectus?

The first Homo erectus fossils recorded by Eugene Dubois came from Java.  Dubois was not so good at recording the geological context of his finds, and most of the later Javan discoveries were by local farmers.  Consequently the dates of first arrival of the erects are a subject of continual debate, recent suggestions being that erects maintained a hold in Indonesia until as late as 20 thousand years ago.  The incompleteness of  records also led to few finds of artefacts, so much so that doubt has been cast on any significant H. erectus culture.  Later work throughout Indonesia did reveal something quite astonishing, however.  The erects crossed Wallace’s line to colonise one of the easternmost islands in the Indonesian arc, Flores, where undoubted stone artefacts occur in rich beds of fossil bones.

Alfred Russell Wallace noted that the flora and fauna of western Indonesia are to all intents the same as on continental Asia, whereas those of the islands east of Bali are very different.  This empirical division is now known to have arisen through the emergence of land bridges between the western islands and mainland Asia as sea level fell to expose shallow seafloor during Pleistocene glacial periods.  Wallace’s line coincides with straits that are very much deeper than could ever disappear during falling sea level.  Reaching islands such as Flores demands that H. erectus must have devised means of crossing wide stretches of open sea.  Fission-track dating of zircons gives ages for bone beds with tools that range from 840 to 700 thousand years (O’Sullivan, P.B. et al. 2001.  Archaeological implications of the geology and chronology of the Soa basin, Flores, Indonesia.  Geology, v. 29, p. 607-609).  Erects crossed at least two major seaways to reach Flores, predating the first seafaring modern humans, who reached Australia around 40 to 60 thousand years ago by an enormous span of time.

Unwholesome fare

Since Raymond Dart’s notoriously bloodcurdling views on the dietary habits of early hominids and “the mark of Cain” appeared in his 1950s essay “The Predatory Transition from Ape to Human”, palaeoanthropology has sometimes tried to brush under the carpet evidence for cannibalism among our ancestors.  Considering the many funerary traditions practised today, some of which involve dismemberment and defleshing of corpses, it is easy to pass off cut-marks on fossil bones as indicating last rites.  However, when evidence of cooking turns up (and the Anasazi people of 12^th century Colorado left plenty of evidence for that, including making anthropic soup), the common notice in pub restaurants, “Children served”,  takes on grim undertones.

Tim White, co-director of the Laboratory for Human Evolutionary Studies at the University of California (Berkeley) is a palaeoanthropologist who commands attention.  It was he who discovered evidence for Anasazi cuisine, and has subsequently maintained an interest in assessing evidence for cannibalism.  It does go back a long way, to evidence for the first European’s (H. antecessor) gustatory relish of their fellows at the 800 ka site of Gran Dolina in northern Spain, and similar signs in Neanderthal sites spaced by hundreds of generations.  The questions of, “How often?”, and, “Under what circumstances?”, are difficult to answer.  However, it was a part of the cultures unearthed by excavation.

Source:  White, T.  2001.  Once were cannibals.  Scientific American, August 2001, p. 48-55.

The recent fossil records of the Americas and Oceania are littered with species that became extinct in the last 100 000 years.  The majority of them are large animals whose body weights were greater than 45 kg – part of the megafauna.  While controversy rages about the date of entry of the first humans into both vast regions, for a long time archaeologists have suspected that the appearance of sophisticated hunters was somehow connected with the rapid decline in what would have been prey species.  One theory is that having never encountered weapon-bearing bipeds, large mammals were “naïve” and thus easily slaughtered.  Most visitors to the Americas and Australia soon notice how unafraid many animals are of humans, compared with their behaviour in Europe and Africa.  The suddenness of  the selective extinctions (around 15 to 11 000 and 47 000 years ago in North America and Australia respectively) is astonishing, if the cause was small bands of hunters, and other workers have suggested that human entry brought diseases that wiped out species susceptible to them, but with no immunity. The third main theory is that a sudden shift in climate wrought havoc among large herbivores and predators, by producing a change in vegetation.  The last is difficult to support for the Americas as the extinctions were in a period of increasing warmth and humidity following the termination of the last glacial period.  As always, new information from research directed at the problem has narrowed the choices, but revealed complexities.

Modelling the influence of changing predation on prey stems from the mathematical simplification of reality by Lotka and Volterra, in which “boom and bust” events pop out of the simulations.  John Alroy of the University of California applied an advanced version of the basic model to the likely effects of advanced hunters appearing suddenly in North America (Alroy, J.  2001.  A multispecies overkill simulation of the end-Pleistocene megafaunal mass extinction.  Science, v. 292, p. 1893-1896).  His model assumes slow human population growth, random hunting and the least possible effort – a conservative approach.  The results closely parallel the record, if human population expanded from 100 first entrants about 14 000 years ago to almost 1 million 750 years later, and suggest that a steady state population of around half that co-existed with the surviving fauna until the appearance of Europeans and their culture.  It is an entirely mechanistic model, but mimics what happened without recourse to any other influence, such as climate change.  So far, no human site in the Americas has been convincingly dated before 14 000 years ago.

Dating is even more of a problem in Australia, particularly for human arrival.  The earliest dated fossil is 60 000 years old (see Out of Africa hypothesis confounded? EP Feb 2001), but claims have been made for artefacts at least twice that age.  Alroy’s model applied to Australia would demand extinction (24 out of 25 genera Pleistocene megafaunal species) shortly after earliest arrival.  A large team of Australian scientists (Roberts, R.G. and 10 others 2001.  New ages for the last Australian megafauna: continent-wide extinction about 46 000 years ago.  Science, v. 292, p. 1888-1892) have systematically dated the age of burial of extinct faunas at 27 sites in coastal areas and the more humid SE of the continent (none from the vast, arid “red centre”), and one in Papua New Guinea.  The most likely interval for the extinctions, between 39 800 and 51 200 years ago, bears no relation to extreme aridity during the last glacial maximum, so the data weigh against that climatic cause.  However, the last 100 000 years have seen lesser, but still extreme shifts in climate, so climate change cannot be ruled out.  Though the authors also do not rule out humans eating their way through Australias bizarre megafauna, the lag between evidence for first entry and the extinction seems far longer than that in the Americas.  Closer inspection of their data, however,  does show precise ²³⁰Th/²³⁴U ages (+ 600 to 2 200) from 33 600 to 60 000 from 3 sites, and less well-constrained luminescence ages (+ 200-21 000) from 16 000 to 171 000 years from all the sites.  Applying simple statistics to samples from such a wide spread of localities does not seem justified to me – normal practice is for ages at individual sites to be accepted as dates within the errors of the method used.  Australia’s megafaunal extinction seems to have been protracted.  Using fuzzier dating of the extinction, earlier workers correlated it with evidence for an increase in bush fires marked by ash in offshore sediments.  Much of Australia’s flora is fire resistant, and the seeds of some species require light burning before they will germinate.  The most popular theory for the extinctions there is through deliberate fire setting by hunters – a culturally induced decline unique to Australia’s peculiar climate and terrain.

See also:  Dayton, L.  2001.  Mass extinction pinned on Ice Age hunters.  Science, v. 292, p. 1819.

The drying of East Africa’s climate since 5 Ma ago shifted the distribution of its ecosystems towards more widespread savannah.  In the most general sense that probably created conditions for ape speciation towards an upright gait and the potential for tool-using and growing consciousness that palaeoanthropologists visualize at the core of human evolution.  The apparently dominant influence of North Atlantic circulation changes on climate fluctuations since then has suggested to many climatologists that the shift to glacial-interglacial and dry-humid cycles, at high and low latitudes, stems from some trigger for a fundamental shift in that circulation.  The favoured process is the closure of open connection between Atlantic and Pacific Oceans when the Isthmus of Panama formed about 5 Ma ago.  That transformed Atlantic circulation, and probably set in motion the Gulf Stream.  However, there are several such gateways whose affects on ocean circulation link to plate movements.

One is the narrow passage between Indonesia and Australasia, which transfers Pacific water to the Indian Ocean.  Subduction permits Australasia to move gradually northwards, thereby narrowing the gateway and also shifting it relative to the major currents in the tropical Pacific.  Mark Cane and Peter Molnar of Columbia University and MIT have analysed the recent evolution of the Indonesian gateway (Cane, M.A. and Molnar, P.  2001.  Closing of the Indonesian seaway as a precursor to east African aridification around 3-4 million years ago.  Nature, v. 411, p. 157-162).  Their findings suggest that the main flow switched from warm, South Pacific surface waters to cooler waters that originate in the North Pacific at about 4 Ma.  Cooling of surface waters in the Indian Ocean would have reduced the amount of water vapour transferred to the air masses that are involved in the East African monsoons.  The reduction in seasonal rainfall would have dried that area substantially.  Though providing a plausible cause for regional climate change, the coincident transformations of two major ocean gateways adds greater complexity to the Plio-Pleistocene climate system.  In terms of modern climate, the Indonesian gateway provides a means of understanding the teleconnection that seems to exist from correlation between drought-flood cycles in East Africa and the El Niño – Southern Oscillation in the tropical Pacific.

See also: Wright, J,D. 2001.  The Indonesian valve.  Nature, v. 411, p. 142-143.

Multiregionalists nailed by Y chromosome?

One of the big problems in using genetic material from living people to chart relatedness, and perhaps evolutionary origins, is simply getting the material.  For the mitochondrial DNA studies that first hinted at a common African origin for all modern humans, the best material is placental tissue.  A focus on male lineage using Y chromosomes is not so difficult; it can be done using blood samples.  Nonetheless, a survey based on 12,127 samples from 163 population is a monumental achievement (Ke, Y. and 23 others  2001.  African origin of modern humans in East Asia: a tale of 12,000 Y chromosomes.  Science, v. 292, p. 1151-1153).

The significance of this study by a large team from China, the USA, Indonesia and Britain is that it focuses on the region most favoured by multiregionalists for the hypothetically separate descent of modern humans from ancient ancestors of Homo erectus stock in different parts of the Old World.  The male chromosomes all carry evidence of mutations to a Y-chromosome marker that originated in Africa, abetween 35 to 89 ka ago.  The huge mass of data from the whole of East Asia do not support even minimal contribution from any source other than one that originated in Africa around the time it is thought that fully modern humans began to leave in significant numbers.

As if the jumble in cladistics of African hominins was not enough, the skull SM3, dubbed by some as “Java Girl”, adds to the bag of spanners that disrupts attempts to rationalise the human evolutionary bush  (See Earth Pages Apr 2001, Skulduggery, migration and confusion).  Java, of course is where the whole thing began, with Eugene Dubois’ (See Review of Pat Shipman’s biography of Dubois in Nature v. 410, p. 869) discovery of what seemed to him as Darwin’s “missing link”, in the form of Pithecanthropus (now Homo) erectus in 1892.  Miss palaeo-Java, is odd by comparison, largely because her brow ridges did not meet and her forehead was “nobly” high.  Morphologically, her skull shows features that could be transitional between H. erectus and H, sapiens.  New Scientist ran an article (Soares, C.. Talking heads.  New Sientist, 14 April 2001 issue, p. 26-29) that charts how her skull, found recently in a New York antique shop – she was smuggled out of Indonesia two decades ago, has been grist to the mill for the multiregionalists, already gleeful at the DNA sequence of Australia’s “Mungo Man” (See Earth Pages Feb 2001, Out of Africa hypothesis confounded?).  Thoughtfully, Christine Soares also mentions the growing doubts that shapes of skulls and even whole skeletal anatomies can contribute a great deal resolving the multiregional vs out-of-Africa debate.  This arises from Todd Disotell’s studies of  modern monkeys, where he found that genetically distant species had almost identical morphologies, whereas much more closely related species were the most different from each other cranially.

Impacts and human evolution

Few Earth scientists disagree with the notion that our planet’s evolution and that of its life has been repeatedly punctuated by catastrophic impacts with comets and asteroids.  The Moon’s surface is an excellent record of that bombardment in near-Earth space since about 4.45 Ga ago, when it formed in orbit around the Earth.  Both dating of impact glasses from the Apollo programme and assessment of the relative ages of lunar craters provide continually refined statistics of the distribution of impact events of different magnitudes through time.

Dr Benny Peiser, a social anthropologist at Liverpool John Moores University and Michael Paine, an impact researcher from the Planetary Society in Australia, applied these statistics to the roughly 5 Ma time span of human and hominin evolution.  Their suggestions were presented by Peiser at the Charterhouse Conference 2001 “Celebrating Britain’s Achievements in Space” in London (see the Cambridge Conference Network  archives at http://abob.libs.uga.edu/bobk/cccmenu.html .

They calculate that 552 impacts that formed craters between 5 and more than 20 km across occurred on land during human evolution, with an additional 6 ocean impacts that could be expected to produce moderate to severe global climate disruption. So far, 32 impact craters have been discovered that are younger than 5 million years.  Earth’s active erosion and sedimentation are like to have obscured more craters, even in such a brief period.

No-one would seriously dispute Peiser and Pain’s calculations, but where they proceed from them is a different matter.  They assign an impact origin to the genetic bottlenecks, which seem to be implicated in speciation and which show up in modern human gene sequences (see More molecular evidence for Cro-Magnon migration into Europe – Earth Pages Jan 2001 – and Eve never met Adam – Earth Pages Nov 2000).  No doubt the aftermath of sizeable impacts would place terrestrial life under considerable stress, but to jump from impact statistics to a hypothesis of external causes for hominin speciation is not likely to find much support.  It does not use evidence at all, but probabilities, as often quoted that each of us is as likely to perish from extraterrestrial impact as from a firework accident or murder.

The record of human evolution is blurred to a large degree by:

1.  the tiny number of fossils

2.  the dates assigned to those fossils

3.  the significance assigned to their morphology by different palaeoanthropologists – there are “lumpers” and “splitters”

4.  the total lack of knowledge about the interplay between physiology, culture and social interaction, as regards what constituted “fitness” in natural selection.

Aside from the bottlenecks implied by modern human genetic diversity, or rather lack of it, we do not have a clue when Orrorin, “Lucy” , H. erectus, “Bonzo” the chimp or fully modern humans appeared as species.  And there is another matter; the post-Miocene period has been punctuated by climatic shifts of dreadful magnitude that came thick and fast through Milankovich pacing.  To suggest any other trigger for speciation, without a “smoking crater” and a precise date coinciding with the first individual of a species, is neither sensible nor necessary – as if…  This is grandstanding, and the press have had a field day.

New human evolution web site

Science magazine’s NetWatch (10 April 2001) includes news of the Becoming Human web site developed by the Institute of Human Origins at Arizona State University.  http://www.becominghuman.org is multimedia, including a 30 minute “webcast” by Donald Johanson, the director, who found “Lucy” in 1974.  That can be skipped, and the meat found in various Exhibits, a glossary, references, links and news.  The site plans to launch a teachers’ resource centre in May.

March was a fertile month for news concerning human origins and evolution.  The good news is that the palaeoanthropologists are at each other’s throats again!  I think it is good news because many of them have an air of smugness and triumph, and they get far more money than other Earth scientists (with the exception of those bent on finding a banth on Mars).  Tangling with hominins in Kenya is a sure route to trouble, as the finders of “Millenium Man” (Ororrin tugenensis) – Martin Pickford and Brigitte Senut now discover (Butler, D.  2001.  The battle of Tugen Hills.  Nature, v. 410, p. 508-509).  Not only is their claim that the 6 Ma old fossil is the oldest on the route to humanity hotly disputed (Aiello, L.C. and Collard, M.  2001.  Our newest oldest ancestor?  Nature, v. 410, p. 526-527), but has ended with their taking suit against Richard Leakey and the Kenyan National Museums for unlawful arrest, false imprisonment and malicious harassment over claims that they poached the site where Orrorin was found.  Never an easy atmosphere in which to work, human evolution is now one posing considerable dangers, so much so that some specialists will comment only anonymously.

Books in the field always sell like hot cakes, as much for the intrigue and the chutzpa as for the science that they convey.  Reviewers become drawn into the hype, despite their best intentions (White, T.D. 2001.  Adventures in the Bone Trade: the Race to Discover Human Ancestors in Ethiopia’s Afar Depression, by Jon Kalb.  Nature, v. 410, p. 517-518).  Areas in Afar and Danakil are physically dangerous because of current hostilities between Eritrea and Ethiopia, and dissatisfaction among the local people.  But they have enormous potential for hominin discoveries following those of “Lucy” and Ardepithecus.  On a recent visit to Eritrea I heard rumours of what might amount to claim jumping and attempts to acquire material clandestinely from new and potentially productive sites, hopefully without foundation.

Confusion is washing over hominin cladistics as ever more variants of accepted species, and fossils that seem to warrant new species and genera turn up.  This is particularly rife for early remains that predate the first stone tools (Lieberman, D.E. 2001.  Another face in our family tree.  Nature, v. 410, p. 419-20; Balter, M. 2001.  Fossil tangles the roots of human family tree.  Science, v. 291, p. 2289-2290; ).  Of course, much of the confusion stems from every new find seeming to bear different cranial and dental hallmarks, combined with dogged attempts to chart the path of our descent through the remains and a tendency to change genus and species names (Homo habilis is now sometimes assigned to Australopithecus, despite a probable association with primitive stone tools).  The latest bush figured by Lieberman is notable for every supposed cladistic link being marked by a query.  One gets the impression of rather too much shuffling around of anatomy, and too little consideration of the unseeable, but inevitably vital distinction between the human line and other fossils.  There are still very few hominin fossils!

Tools demand consciousness, and probably social links far stronger than those of other apes.  Only stone tools survive, from around 2.5 Ma ago, but must represent an advanced culture that arose from earlier beginnings.  Abstracting usefulness from surrounding nature and social organisation confer such advantages to its inventors that they set them apart from other animals in relation to natural selection.  Fitness no longer applies to the individual organism, but increasingly to its culture shared with others.  The formerly unfit becomes fit, and that can play havoc with physiological diversity and thereby the cladists’ shuffling.

Culture confers something equally powerful by enabling its carriers to diffuse beyond their geographic range.  The 2 March 2001 issue of Science devotes 33 pages to human migrations (Culotta, E, Sugden, A and Hanson, B. (eds)  2001.  Humans on the move.  Science, v. 291, p. 1721-1753).  For me, this is the most powerful and informative contribution to our self-knowledge in many years.  Eight articles cover the earliest Europeans, the relations between modern humans and Neanderthals, the first colonisers of the Americas, the roles of genetics in teasing out our origins and how tools track physiological change.  Appearing in the midst of tedious and self-regarding squabbles among the “bone people”, it surely marks a proper line of march in this abidingly gripping branch of Earth science.

February 2001 saw the public release of the human genome, with entire issues of both Nature and Science substantially devoted to discussion of its implications, educational CDs and wall charts.  That is if the huge wadge of adverts capitalising on the genome’s release is discounted  Pundits have latched onto the fact that humans seem to possess not that many more genes (around 30 000) than grass, a worm or a fruit fly, making comments about how humbling that is.  Vastly outnumbering protein-coding genes are “snips” (single nucleotide polymorphisms – SNPs), and humans have around 1.4 million of these and possibly far more in the 3 billion sequences of four nucleotides.

The huge variability of “Snips” holds excellent prospects for deeper understanding of human origins and evolution, previously (and unsatisfactorily) addressed by using DNA in mitochondria and the Y chromosome.  Previous means of establishing molecular  “distance” to indicate relatedness and the times of divergence from last common ancestors rely on DNA that occurs only once in each cell, and does not undergo division and recombination during sexual reproduction, so that it is passed on in the female or male line of descent.  Whereas such haploid material is relatively easy to analyse and interpret, it behaves like a single gene.  Differences arise through natural selection or chance events that affect only one item.  That makes it possible only to address the history of one variable, rather than that of a whole species or a population – a single thread rather than the multitude that must constitute the signal of real events.

“Snips” potentially can help resolve the out-of-Africa and multiregional hypotheses for the origin and spread of fully modern humans, and even whether we do carry vestiges of other groups of the genus Homo, such as the Neanderthals or various groups of more archaic beings who began to leave Africa for the rest of the Old World around 1.8 Ma ago.  In a review of the possibilities, Mark Stoneking of the Max Planck Institute in Leipzig (Stoneking, M. 2001.  From the evolutionary past…  Nature, v. 409, p 821-822) cautions that much remains to be done before SNPs can really give believable information.

Living humans are anatomically the most diverse animals of a single species on the planet.  The differences extend from limb bones to skull characteristics, including the bony underpinnings of our faces.  That shows up plainly in any crowded market, whether that be in Addis Ababa, Bombay or Birmingham. Yet our genetic make up is extremely narrow, and chimps from separate troupes in West African jungle show greater diversity than that of humans across the world.  When physical anthropologists’ only tool was empirical comparisons between the physiognomies of people from different populations, their findings helped serve a political agenda. Statistical groupings drawn from that diversity slaked racists’ thirst for “proof” of their ethnic group’s wished-for “superiority”.  Such furtive longings are as alive today as they ever were in the 1930s: a mischief based on rubbished pseudoscience and ignorance.  We are physically diverse, but genetically distinguishable only by the most exquisitely precise analyses of DNA and other heritable material.

The minute genetic differences between peoples, like those more obviously separating the languages that they speak, result from migrations across the planet that took place before about 10 thousand years ago.  The migrants lived as hunter-gatherers under the climatically adverse condition of the last ice age.  Before the invention in widely separate centres of animal husbandry and agriculture that allowed human populations to explode – no earlier than 10 thousand years ago – our forebears’ total numbers would have barely exceeded the attendance on a Saturday afternoon at English Premier League soccer matches.  Tiny population densities, coupled with groups living in isolation and the random effect of mutations, with time create genetic differences between these groups, and so too for language and culture.  The narrowness of modern peoples’ genetic diversity points strongly to their last common ancestor living not so long ago in geological terms.  Whereas the earliest anatomical evidence for modern humans – a skull from Ethiopia with the chin that sets us apart from other extinct human species – is 450 thousand years old, differences in DNA from mitochondria indicate that divergence of the female half of our make up was about 140 thousand years ago.  Evidence from living men’s Y chromosomes (see November 2000 Earth Pages Eve never met Adam) suggests an even more recent stem, about 70 thousand years ago.  Both analyses point strongly to Africa for the focus of later divergence, that no other lines of descent survived to the present, and that no DNA from different groups, such as Neanderthals or Homo erectus, was involved in living peoples’ ancestors since 140 thousand years ago.  These observations form the core of the “Out of Africa” hypothesis.

There are, however, physical anthropologists who still set great store by statistical analysis of anatomical features, specifically that of skulls from extant humans and fossil ones.  They hold a view that it is possible that modern human’s physical diversity arose by evolution from much older populations of earlier migrants to different regions from Africa – the “Multi-regional” hypothesis explored by Milford Wolpoff of the University of Michigan.  In the case of Asian and Australasians that might have been from H. erectus that arrived in China as long ago as 1.8 million years back – recent dating of sediments in which erects’ remains have been found in Indonesia shows that they survived until as recently as 20 thousand years ago.  Alternatively it could have been from more advanced humans who arrived in Asia less than half a million years ago; the Mapas whose remains resemble those of Neanderthals.  For Europe, the putative ancestors would be Neanderthals, who arrived there at least 350 thousand years ago.  Africans, say the multi-regionalists, evolved continuously from the earliest tool-using humans since 2.5 million years ago.

Wolpoff’s group has used the same statistical technique employed in DNA studies to analyse skull morphologies from 25 individual modern humans from the fossil records of Europe and Australia, and compared the results with those for well-accepted, earlier humans and modern ones from Africa.  They claim (Wolpoff, M.H. et al. 2001.  Modern human ancestry at the peripheries: a test of the replacement theory.  Science, v. 291, p. 293-297) a better statistical fit between data for pairings of modern-human and earlier inhabitants of Australia and Indonesia, and of Europe than between modern-human remains from different regions.  “Out of Africa” proponents question the validity of the method, particularly selection of parameters – facial characters are omitted – and actual fossils.  Statistics is always a problem in studying human fossils, because they are so rare and widely separated in time – the study by Wolpoff’s group used material ranging from 60- to 14 thousand years old, and a total of only 25 specimens.

Even rarer are data for genetic material separated from fossils.  Three years ago, palaeoanthropologists at the Max Planck Institute in Munich reported the first partial DNA sequence from Neanderthal remains, later confirmed by another extraction.  They showed how unlikely it is that conjugation of Neanderthals and contemporary modern humans resulted in any signature surviving in the genes of living people.  Likewise, the data seemed to rule out any relatedness between the two groups since possibly several hundred million years ago; bad news for the multi-regionalists.  Astonishingly, scientists at the Australian National University have recovered useful DNA from 10 fossil humans between that range from 2 to 60 thousand years old.  The oldest not only represents the earliest Australian yet found, but turned out to be very different from that of later inhabitants (Adcock, G.L. et al. 2001.  Mitochondrial DNA sequences in ancient Australians: Implications for modern human origins.  Proceedings of the National Academy of Sciences, v. 98, p. 537-542).  One intriguing aspect is that a sequence in the mitochondrial DNA of “Mungo Man” exists as a remnant “insert” in modern DNA from chromosome 11, long suspected of being old mtDNA that has transferred to that in the cell nucleus.

Although no-one claims “Mungo Man” was an ancestor of living native Australians, there is many a spin that can be placed on the discovery.  The spanner in the works is that he is physically modern, beyond a shadow of doubt for comparative anatomists, but genetically archaic.  One possibility, espoused by the multi-regionalists, is that he evolved from pre-modern human migrants into Asia, either H. erectus or Mapas.  But that runs against the discovery of morphologically erect fossils from Indonesia that are much younger.  Perhaps he descended from interbreeding between early modern human migrants with earlier Asians, his DNA failing to be passed on to the present.  It is also possible that 60 thousand years ago, humans had a much greater range of genetic diversity, and that was filtered to today’s narrowness by a “bottleneck” due either to a disastrous fall in global population or to a cultural innovation that favoured only those who used it in the lottery of evolutionary fitness.  Though grist to the multi-regionalist mill, one DNA datum does not knock the “Out of Africa” hypothesis from its basis on thousands of results from living people.  Humans in one shape or other trekked from Africa to Asia at least three times since 1.8 million years ago, surviving in the case of the erects until quite recently.  It is what tool-equipped, socially conscious beings do, because they are sheltered from environmental pressures by what they do as much as by who they are.  That also surely means that all manner of changes in their genes and their morphology, which in mere beasts might snuff them out, can survive to confound the pure anatomist and the molecular biologist.  As the demise of the Neanderthals shows, when cultures are pitted in environments that offer limited resources, one gives way to another better suited.  Sadly, lifestyles and outlook, that we know to have driven human history for 6 000 years or so, leave little fossil record save stone tools and art, often inexplicable.  Accepting what makes humans unique has somehow to figure in all the empiricism around which centre current ideas on our origins.

(See also: Pennisi, E.  2001.  Skull study targets Africa-only origins.  Science, v. 291, p.231.  Dayton, L.  2001.  The man from down under.  New Scientist, 13 January 2001 issue, p. 6.  Holden, C.  2001.  Oldest human DNA reveals Aussie oddity.  Science, v. 291, p. 230-231)

For two weeks in December both adults and infants in Britain have been plagued by nightmares figuring the superb prosthetic and dramatic reconstruction of a Neanderthal family in Channel 4’s Neanderthals.  As London University human geneticist, Steve Jones, has observed, “If you met an unwashed Cro Magnon dressed in a business suit on the Underground, you would probably change seats.  If you met a similarly garbed Neanderthal, you would undoubtedly change trains”.  Of course, the big issue is not that Neanderthals were muscled hulks with gigantic noses, beetling brows and little in the way of chins, but who were the interlopers that drove them to oblivion?  Apart from the fact that Neanderthals portrayed Cro Magnons as being pretty cool, with a trendy line in face paint, there is little doubt that their only advantage over the chinless ones was one of lifestyle.  Being migrants from Africa via the Middle East, Cro Magnons had to have been nomadic hunter gatherers.  Neanderthals had survived at least two full ice ages in Europe, and subsisted from fixed ranges around their homes.  Game husbandry in a severe climate meant two things: small Neanderthal bands supported by large ranges, and little communication with neighbouring bands.  Entry of nomadic hunters into ranges inevitably depleted resources for the territorial first occupants, without the two groups even coming into direct conflict.  Nomads can move to fresh hunting grounds, thereby avoiding starvation.

Recent molecular studies of modern mens’ Y chromosomes (see also Eve never met Adam, October-November 2000 Earth Pages) confirms archaeological evidence that the sad drama of Neanderthal decline and eventual extinction began with the entry of fully modern humans about 40 000 years ago (Semino, O. et al., 2000.  The genetic legacy of Paleolithic Homo sapiens sapiens in extant Europeans: a Y chromosome perspective.  Science, v. 290, p. 1155-1159).  Eighty percent of modern European mens’ Y chromosomes stem from two ancient haplotypes.  The divergence can be calculated to have occurred around 40 ka from one now vanished, apart from its trace in molecular relatedness.  That trace itself is related to another, older one, found in modern Siberian and native peoples of the Americas.  It looks as if migrants from Africa remained fixed for a long time in the near East, then to move west and east as the climate cooled.  It was the carriers of the now dominant European male Y chromosome that interacted ecologically with the Neanderthals, to the extent that the latter died out.

The molecular statistics suggests that these early “Aurignacian” people – named after their stone-tool culture recovered from archaeological sites – dominated northern Europe.  Deepening glacial climate forced them into refuges in the Ukraine and Iberia during the last glacial maximum around 24 to 16 ka ago.  At this climatic low point, a further migration into southern Europe emerges from the genetic analyses; that of a population which probably brought in the more advanced “Gravettian” culture.  They too survived in a refuge, but in the Balkans.  The fact that the Aurignacian genetic trace is so dominant among European men today probably signifies that its population moved rapidly out of its refuge areas, growing numbers re-stocking much of the continent left empty by the demise of the Neanderthals.

Considering the explosive influence of an entirely different culture on the history of Europe during the last 10 thousand years – that of agriculture – it comes as a great surprise that genetic evidence of its likely source is restricted to at most 20 % of modern Europeans.  Four new mutations can be dated to have appeared around 9 000 years ago, at the beginning of the Neolithic explosion from which all modern economies date.  They almost certainly arose in the “fertile crescent” of the Middle East where farming first shows in the record around that time.

In the same way that Channel 4’s Neanderthals came to be made, the evidence needs imagination to enliven it.  One thing does seem likely; the earliest modern Europeans probably learned their farming, and possibly much else besides, from a trickle of new immigrants, once climate had finally improved to a near-modern state.  More intriguing is to wonder why the earliest Cro Magnons were moved to walk into an increasingly frigid Europe in the first place.  Were they pariahs in what became the “fertile crescent”?  Did they get sick of oppressive “Big Men” who ruled the roost there?  Incidentally, that seems to have spurred much of the historical movement of peoples in Africa.  Or, did drying at low-latitudes, which accompanied more northerly cooling, mean that worsening conditions in the Middle East demanded urgent migration in any direction that presented itself?  Perhaps we shall see a drama relating this story, and the sudden explosion of art at the depth of an ice age.  An expression of relief and celebration of good luck?

See also:  Gibbons, A.  2000.  Europeans trace ancestry to Paleolithic people.  Science, v.  290, p. 1080-181

Discovery of huge primate buttock print

The search for the Sasquatch is a story that runs and runs.  Generally it has been stoked up by dubious evidence, such as plaster casts of gigantic footprints and a film of a rather portly and somewhat camp being striding through the woods of Washington State.  Scorn poured on “Bigfoot” research by zoologists and anthropologists may have to be retracted after the latest revelation (Kleiner, K.  2000.  Bigfoot’s buttocks.  New Scientist, 23/30 December 200 issue, p. 8).

The Bigfoot Field Researchers Organization set out in September to lure a Sasquatch with a mixture of pheromones (whose, I wonder!), supposed cries of wandering, pedally challenged anthropoids, and…. apples.  The trap was laid in a muddy clearing in the Gifford Pinchot National Forest of southern Washington state.  The following day, researchers found an impression interpreted as that made by forearm, hip, thigh heel and a gigantic, hairy bottom, as if some naked… thing… had sat down to munch the bait.

Now this is exactly what I would have needed to sustain my early belief in Santa Claus; something going beyond the drained sherry glass and crumbs of cake on the hearthstone.  Using comparative anatomy, the prints suggest a being more than 2.5 metres tall, in keeping with the well-known size 24 feet.  Personally, I get the whiff of smoked fish, because the heel print bore markings remarkably like those of human fingerprints.  As they say, the jury is still out….., probably having a stiff drink.

The world was shocked when Armin Meiwes of Rotenburg, Germany admitted eating his pen pal, the more so when he convinced his trial jury that his friend was a willing menu item.  However, so bizarre was their mutual obsession that ordinary folk could rest easy that human cannibalism was an aberration or born of necessity; no need for nervous glances at your neighbourly gourmand.  Every time earlier human remains that show signs of cut marks or having been boiled in the proverbial pot emerge the “necessity” card or that of burial practices are played in the storm of controversy surrounding possibly unwholesome aspects of older cultures.  That is not so easy when forensic pathology is applied to cooking utensils and fossilised dung, spanning several hundred years, and finds traces of protein that can only have come from deep muscle tissue (myoglobin), as occurred in archaeological investigations in pre-Columbian Colorado.  But there is worse, as recounted by Richard Hollingham (Natural born cannibals.  New Scientist 10 July 2004, p. 31-33).  Hollingham reviews recent research that has cannibalistic themes.  The truly grim findings were made by a group at University College, London, who have studied a brain disease related to the variant CJD induced in humans who ate BSE-infected beef (Mead, S. et al. 2003.  Balancing selection at the prion protein gene centre consistent with prehistoric Kuru-like epidemics.  Science, v. 300, p. 640-643).  Kuru affected the Fore people of highland Papua New Guinea, who ritually ate dead relatives’ brains, before the authorities banned the practice, and is caused by rogue proteins known as prions.  In that respect it is similar to vCJD, BSE and a number of other mammalian brain disorders.  The UCL group studied the genetic effects of Kuru on the Fore, to see if any immune resistance to prion infections had developed.  There are two genes linked with prions, and people who possess both have greater resistance to vCJD, whereas people having only one are susceptible.  In the Fore study,  a surprising 75% of women (usually the main consumers of human brain tissue) had both, which the team put down to evolutionary pressure that had resulted from thousands of years of the practice.  Turning to genetic data from different ethnic groups world-wide, they found such heterozygotes were widespread, although with different proportions in different groups.  Even though these global populations do not generally eat other people now, there is a distinct possibility that their distant ancestors did, for a very long time.  That is welcome news that counters the fears of massive vCJD epidemics from eating animals unnaturally fed on animal protein.  What is wholly disturbing is that for much of human evolutionary history cannibalism was unnecessary for survival, and Miewes, in his initial police statement, claimed that there are around 800 cannibals in Germany alone…..