Massive hominin skull from China: is it a Denisovan?

In 1933 labourers unearthed a very large skull during the construction of a bridge near Harbin, Northern China. At that time, the area was under occupation by Imperial Japanese forces. To keep it out of the invaders’ hands the skull was quickly wrapped in a cloth and hidden in an old well. It was only in 2018 that the original finder’s grandson recovered it to pass on to archaeologists at  Hebei Geo University. It lacks a lower jawbone, so technically it is a cranium, but is very well preserved. The face has very large brow ridges – generally taken as a primitive feature – but also some more modern features. With a 1,420 ml brain case, it is significantly larger than most modern human crania. Apparently, it is of an adult male. As well as a big head, he had a large nose, as do Neanderthals: a possible adaptation to very cold conditions. Without waiting to see if the bones might yield DNA, five of the team who examined the cranium claimed it as a new species, Homo longi or ‘Dragon Man’; i.e. distinct from modern humans and Neanderthals and all known older hominins (Ni, X. et al. 2021. Massive cranium from Harbin establishes a new Middle Pleistocene human lineage in China. The Innovation, v. 2, article 100130; DOI: 10.1016/j.xinn.2021.100130. Ji, Q. et al. 2021. Late Middle Pleistocene Harbin cranium represents a new Homo species. The Innovation, v. 2, article 100132; DOI: 10.1016/j.xinn.2021.100132). They based this phylogenetic interpretation on morphology alone. At least one of the team, Chris Stringer a leading hominin palaeoanthropologist at The Natural History Museum in London, demurred. The cranium is not unique and bears close similarity to another from the central Chinese province of Shaanxi, which was found in the late 1970s. In fact there are three other Chinese crania that resemble that from Harbin, although they are less well preserved.

All-sided views of the Harbin cranium. (Credit: Ni et al., Fig 2)

Dating the fossil was not easy, as the site where labourers discovered him was destroyed during construction of the bridge. Researchers used a variety of geochemical analyses, including from sediment stuck in his nasal cavity, to derive a likely stratigraphic profile from which the cranium may have been excavated. The best fit is with Middle Pleistocene sediments in the Harbin area. Uranium-series dating of the bone suggests that it is older than 146 ka (Shao, Q.  et al. 2021. Geochemical locating and direct dating of the Harbin archaic human craniumThe Innovation, v. 2, article 100131; DOI: 10.1016/j.xinn.2021.100131). So it is likely that this man and his companions did not cohabit China with anatomically modern humans, who arrived no more than about 50 ka ago. The highly robust nature of all the similar crania suggests that the individuals must have been large and physically active. Like the Neanderthals, they had adapted to harsh conditions over several hundred thousand years of repeated climate change. Even today, winters in northern China average around -16°C, and far inland conditions are semi-arid to arid. For them to migrate would have involved traversing some of highest, bleakest passes in the world. These people evolved to survive extreme climatic and environmental change, much as did the Neanderthals in West Asia and Europe. By comparison anatomically modern humans evolved in the more stable environments of Africa and the Middle East, surviving only the last ice age once they had migrated northwards. Those who made it to northern Siberia and crossed the Bering Strait via Beringia around the last glacial maximum did evolve physical traits that helped them survive, but minor ones compared with the earlier humans.

So what do these Chinese fossils represent? Using cranial features alone to propose distinct species smacks of the techniques of 19th and early 20th century anatomical anthropologists, albeit with powerful statistical analysis. We know that anatomically modern humans carry genetic signatures of interbreeding with at least two known ‘species’ with whom they cohabited Eurasia – Neanderthals and Denisovans. Indeed, traces in  the DNA of living African and Eurasian humans hint at other unknown and probably very ancient ‘ghost’ populations. Genetic, physical and probably cultural differences did not deter repeated interbreeding with these ‘others’. To be frank, erecting new human ‘species’ these days seems to serve little purpose. ‘Dragon Man’ is just as likely to represent the Denisovans as the fully sequenced DNA from a couple of bones from caves in Siberia and Tibet. The latter matched stretches of the DNA from living people of East Asia and parts of the Pacific. There are no other such live genetic tracers awaiting a different candidate to fill the role that we know Neanderthals and Denisovans to have filled. That may yet change, but the first job for the mainly Chinese consortium of scientists is to get genetic material from these crania and sequence it, or invite other highly successful palaeogeneticists who would leap at the opportunity.

See also: Jones, N. 2021. Mysterious skull fossils expand human family tree — but questions remain. Nature, v. 595, p. 50; DOI: 10.1038/d41586-021-01738-w

Sample I. 2021. Massive human head in Chinese well forces scientists to rethink evolution. The Guardian, 25 June 2021.

The early signs of counting and arithmetic?

Three earlier articles in Earth-logs originally focussed on what I supposed to be ‘ancient abstract art’.  One highlighted a clam shell that bears carefully etched V-shapes found at the type locality for Asian Homo erectus at Trinil on the Solo River, Java, dated between 430 and 540 ka. Another is about parallel lines etched on a piece of defleshed bone from China dated at 78 to 123 ka, which may be a Denisovan artefact. The most complex is a piece of ochre found in the coastal Blombos Cave 300 km east of Cape Town, South Africa in association with tools ascribed to early modern humans who lived there about 73 ka ago. Fascinating as they seemed at the time, they may hold much greater significance about early-human cognitive powers than about mere decoration. That is thanks to recent evaluation of other simple artefacts made of lines and notches by anthropologists, cognitive scientists and psychologists. Their work is summarised in a recent Nature Feature by Colin Barras (Barras, C. 2021. How did Neanderthals and other ancient humans learn to count? Nature, v. 594, p. 22-25; DOI: 10.1038/d41586-021-01429-6). The European Research Council recently allocated a €10 million grant to foster research into ‘when, why and how number systems appeared and spread’.

Examples of ancient ‘abstract’ art. Top – V-shaped features inscribed on 430-540 ka freshwater clam from Java; Middle – parallel lines etched through red ochre to show white bone, from a possible Denisovan site in China; Bottom – complex inscription on a tablet of iron-rich silcrete from South Africa

Straight lines and patterns made from them are definitely deliberate, whatever their antiquity. In recent times, such devices have been used by artists to render mental images, moods and thoughts as simplified abstractions: hence ‘abstract’ art, such as that of Piet Mondrian and Kazimir Malevich. The term also applies to the dribbles and drabbles of Jackson Pollock and many more styles. But these works are a very recent evolutionary development out of earlier schools of art. So deliberate geometric shapes and arrangements of lines that are many millennia old cannot simply be termed ‘abstract art’. It is certainly not easy to see how they evolved into the magnificence of Palaeolithic figurative cave art that started at least 40 thousand years ago; Yet they are not ‘doodles’. Being so deliberate suggests that they represented something to their makers. The question is, ‘What?’

The research summarised by Barras is mainly that of Francisco d’Errico of The University of Bordeaux, France and colleagues from Canada and Italy (d’Errico, F. et al. 2018. From number sense to number symbols. An archaeological perspective. Philosophical Transactions of the Royal Society B, v. 373, article 2160518; DOI: 10.1098/rstb.2016.0518). They focused their work on two remarkable artefacts. The oldest (72 to 60 ka), from a cave near Angoulême in France, is a fragment of a hyena’s thigh bone that carries nine notches. It is associated with stone tools almost certainly made by Neandethals. The other, from the Border Cave rock shelter in KwaZulu-Natal in South Africa, is a 44 to 42 ka old baboon’s shin bone, which carries a row of 29 prominent notches, and a number of less distinct, roughly parallel scratches. The rock shelter contains remains of anatomically modern humans and a very diverse set of other artefacts that closely resemble some used by modern San people.

Top: notched hyena femur bone fragment associated with Neanderthal tools from SW France. Bottom: notched baboon shin bone from Border Cave, South Africa. Scale bars(Credit: F. d’Errica and L. Backwell)

Microscopic examination of the notches made by a Neanderthal suggest that all 9 notches were cut at the same time, using the same stone blade. Those on the Border Cave shin bone suggest that they were made using four distinctly different tools on four separate occasions. Are both objects analogous to tally sticks; i.e. to count or keep a record of things as an extension to memory? There are other known examples, such as a 30 ka-old  wolf’s radial bone from the Czech Republic having notches in groups of five, suggesting a record of counting on fingers. Yet very similar devices, made in recent times by the original people of Australia, were not used for keeping count, but to help travellers commit a verbal message to memory enabling them to recount it later.

Do read Barras’s summary and the original paper by d’Errico et al. to get an expanded notion of the arguments being debated. They emerge from the truly novel idea that just because the makers of such objects lived tens or even hundreds of thousands of years ago that doesn’t make them intellectually lacking. Imagining in the manner of Victorian scientists that ancient beings such as Neanderthals and H. erectus must have been pretty dim is akin to the prejudice of European colonialists that people of colour or with non-European cultures were somehow inferior, even non-human. To me it is admirable that the European Research Council has generously funded further research in this field at a time when research funding in the UK, especially for the disciplines involved, has been decimated by those who demanded an exit from the EU.

The older Trinil and Blombos patterns appear yet more sophisticated. The pattern on the latter looks very like the kind of thing that someone in a prison cell might draw to keep track of time. It also incorporates the zig-zag element engraved on the Trinil clam shell. Remember that the word ‘Exchequer’ is derived from a tax audit during the reign of Henry I of England that was conducted on a counting board whose surface had a checked pattern

CSI and detecting the presence of ancient humans

Enter a room, even for a few minutes, and dead skin cells will follow you like an invisible cloud to settle on exposed surfaces. Live there and a greyish white, fluffy dust builds up in every room. Even the most obsessive cleaning will not remove it, especially under a bed or on the bathroom floor. Consider a cave as a home, but one without vacuum cleaners, any kind of sanitation, paper tissues, panty liners, nappies or wet wipes. For pre-modern human dwellings can be added snot, fecal matter, sweat, urine, menstrual blood and semen among all the other detritus of living. A modern crime-scene investigator would be overwhelmed by the sheer abundance of DNA from the host of people who had once dwelt there. CSI works today as much because most homes are pretty clean and most people are fastidious about personal hygene as because of the rapidly shrinking lower limit of DNA detection of the tools at its disposal. Except, that is, when someone from outside the home commits a criminal offence: burglary, GBH, rape, murder. We have all eagerly watched ‘police operas’ and in the absence of other evidence the forensic team generally gets its perpetrator, unless they did the deed wearing a hazmat suit, mask, bootees and latex gloves.

Artistic impression of Neanderthal extended-family life in a cave (credit: Tyler B. Tretsven)

Since 2015 analysis of environmental DNA from soils has begun to revolutionise the analysis of ancient ecosystems, including the living spaces of ancient humans (see: Detecting the presence of hominins in ancient soil samples, April 2017). It is no longer necessary to find tools or skeletal remains of humans to detect their former presence and work out their ancestry. DNA sequencing of soil samples, formerly discarded from archaeological sites, can now detect former human presence in a particular layer, as well as that of other animals. In many cases the ‘signal’ pervades the layer rather than occurring in a particular spot, as expected from shed skin cells and bodily fluids. The first results were promising but only revealed mitochondrial DNA. Now the technique has extended to nuclear DNA: the genome (Vernot, B. and 33 others 2021. Unearthing Neanderthal population history using nuclear and mitochondrial DNA from cave sediments. Science, v. 372, article eabf1667; DOI: 10.1126/science.abf1667). Benjamin Vernot and colleagues from 7 countries collected and analysed cave soils from three promising sites with tangible signs of ancient human occupation. Two of them were in Siberia and had previously yielded Neanderthal and Denisovan genomes from bones. The other is part of the Atapuerca cave complex of NW Spain that had not. The Russian caves yielded DNA from more than 60 samples, 30 being nuclear DNA consistent with that from actual Neanderthal and Denisovan bones found in the caves. Galería de las Estatuas cave in Spain presented a soil profile spanning about 40 thousand years from 112 to 70 ka.

Teasing-out nuclear DNA from soil is complicated, from both technical and theoretical standpoints. So being able to match genomes from soil and bone samples in the Russian caves validated the methodology. The Spanish samples could then be treated with confidence. Galería de las Estatuas revealed the presence of Neanderthals throughout its 40 ka soil profile, but also a surprise. The older DNA was sufficiently distinct from that from later levels to suggest that two different populations had used the cave as a home, the original occupants being replaced by another genetically different group around 100 to 115 ka ago. The earlier affinity was with the ancestors of sequenced Neanderthal remains from Belgium, the later with those from Croatia. That time is at the end of the last (Eemian) interglacial episode, so one possibility is a population change driven by climatic deterioration. This success is sure to encourage other re-examinations of caves all over the place. That is, if there is the analyical capacity to perform such painstaking work in greater volume and at greater pace. Like many other palaeo-genomic studies, this one has relied heavily on the analytical facilities pioneered and developed by Svante Paäbo at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. Covid has forced genetics to the front page for a year and more. And it has led to many advances in anlytical techniques, particularly in their speed. It would nice to think that a dreadful experience may end-up with positive benefits for understanding the full history of humanity.

Relationships between modern humans and Neanderthals

Before 40 thousand years (ka) ago Europe was co-occupied by Neanderthals and anatomically modern humans (AMH) for between five to seven thousand years; about 350 generations – as long as the time since farming began in Neolithic Britain to the present day. Populations of both groups were probably low given their dependence on hunting and foraging during a period significantly colder than it is now. Crude estimates suggest between 3,000 to 12,000 individuals in each group; equivalent to the attendance at a single English Football League 2 match on a Covid-free winter Saturday afternoon. Moving around Europe south of say 55°N, their potential range would have been around 5 million square kilometres, which very roughly suggests that population density would be one person for every 200 km2. That they would have moved around in bands of, say, 10 to 25 might seem to suggest that encounters were very infrequent. Yet a hybrid Neanderthal-Denisovan female found in Siberia yielded DNA that suggested a family connection with Croatia, 5,000 km away (see: Neanderthal Mum meets Denisovan Dad, August 2018); early humans moved far and wide.

The likely appearances of Neanderthals and anatomically modern humans when they first met between 50 and 40 thousand years ago. (Credit: Jason Ford, New York University)

A sparsely populated land can be wandered through with little fear other than those of predators, sparse resources or harsh climate and lack of shelter. But it still seems incredible for there to have been regular meetings with other bands. But that view leaves out knowledge of good places to camp, hunt and forage that assure shelter, water, game and so forth, and how to get to them – a central part of hunter-gatherers’ livelihoods. There would have been a limited number of such refuges, considerably increasing chances of meeting. Whatever the physiognomic differences between AMH and Neaderthals, and they weren’t very striking, meeting up of bands of both human groups at a comfortable campsite would be cause for relief, celebration, exchanges of knowledge and perhaps individuals of one group to partner members of the other.

As well as that from Neanderthals, ancient DNA from very early European AMH remains has increasingly been teased out. The latest comes from three individuals from Bacho Kiro Cave in Bulgaria dated to between 45.9 to 42.6 ka; among the earliest known, fully modern Europeans. One had a Neanderthal ancestor less than six generations removed (perhaps even a great-great grandparent 60 years beforehand). Because of the slight elapsed time, the liaison was probably in Europe, rather than in the Middle East as previously suggested for insertion of Neanderthal genes into European ancestry. The genetic roots of the other two families stemmed back seven to ten generations – roughly 100 to 150 years (Hajdinjak, M. and 31 others 2021. Initial Upper Palaeolithic humans in Europe had recent Neanderthal ancestryNature, v. 592, p. 253–257; DOI: 10.1038/s41586-021-03335-3). The interpretation of these close relationships stems from the high proportion of Neanderthal DNA (3 to 4 %) in the three genomes. The segments are unusually lengthy, which is a major clue to the short time since the original coupling; inherited segments tend to shorten in successive generations. The groups to which these AMH individuals belonged did not contribute to later Eurasian populations, but link to living East Asians and Native Americans. They seem to have vanished from Europe long before modern times. The same day saw publication of a fourth instance of high Neanderthal genetic content (~3 %) in an early European’s genome, extracted from a ~45 ka female AMH from Zlatý kůň (Golden Horse) Cave in Czechia (Prüfer, K. and 11 others 2021. A genome sequence from a modern human skull over 45,000 years old from Zlatý kůň in Czechia. Nature Ecology & Evolution  DOI: 10.1038/s41559-021-01443-x). In her case, too, the Neanderthal DNA segments are unusually lengthy, but indicate 70 to 80 generations (~2,000 to 3,000 years) had elapsed. Her DNA also suggests that she was dark-skinned and had brown hair and brown eyes. Overall her genetics, too, do not have counterparts in later European AMH. The population to which she belonged may have migrated westwards from the Middle East, where one of her ancestors had mated with a Neanderthal, perhaps as long as 50 ka ago. But that does not rule out her group having been in Europe at that time. A later modern human, dated at 42 to 37 ka, is a young man from the Petştera cu Oase cave in Romania, whose forbears mixed with Neanderthals. His genome contains 6.4% of Neanderthal DNA, suggesting that his Neanderthal ancestor lived a mere 4 to 6 generations earlier, most likely in Europe, and was perhaps one of the last of that group.

The data suggest that once modern humans came into contact with their predecessors in the Middle East and Europe, mixture with Neanderthals was ‘the rule rather than the exception’. Yet their lack of direct relationship to later Europeans implies that AMH colonisation of Europe occurred in successive waves of people, not all of whom survived. As Palaeolithic specialist Chris Stringer of the Natural History Museum in London cautions, of these multiple waves of incomers ‘Some groups mixed with Neanderthals, and some didn’t. Some are related to later humans and some are not’. Even five thousand years after ‘first contact’, relations of modern humans with Neanderthals remained ‘cordial’, to say the least, including with the last few before their extinction.

See also: Gibbons, A. 2021. More than 45,000 years ago, modern humans ventured into Neanderthal territory. Here’s what happened next. Science, v. 372, News article; DOI: 10.1126/science.abi8830. Callaway, E. 2021. Oldest DNA from a Homo sapiens reveals surprisingly recent Neanderthal ancestry. Nature, v. 592, News article; DOI: 10.1038/d41586-021-00916-0. Genomes of the earliest Europeans (Science Daily, 7 April 2021). Bower, B. 2021 Europe’s oldest known humans mated with Neandertals surprisingly often (ScienceNews, 7 April 2021)

Snippet: Early human collection of useless objects

The Ga-Mohana rock shelter in North Cape Province, South Africa (Credit: Jayne Wilkins, University of the Witwatersrand)

We all, especially as kids, have collected visually interesting objects for no particular reason other than they ‘caught our eye’: at the beach; from ploughed fields; river gravel, or at the side of a path. They end up in sheds, attics and mantel shelves. In an online News and Views article at the Nature website Pamela Willoughby discusses the significance of a paper on an archaeological site in the southern Kalahari Desert, North Cape Province South Africa (Willoughby, P.R. 2021. Early humans far from the South African coast collected unusual objects. Nature, v. 323, online News and Views; DOI: 10.1038/d41586-021-00795-5). Jayne Wilkins and co-workers from South Africa, Australia, Canada, Austria and the UK have investigated a rock shelter, with floor deposits going back over 100 thousand years. The researchers have, in a sense, continued the long human habit of seeking objets trouvée by using trowels and sieves to excavate the shelter’s floor sediments. They found a collection of cleavage fragments of white calcite and abundant shards of ostrich shell. Ga-Mohana Hill is still a place that locals consider to have spiritual significance. The authors consider the original collectors to have had no other motive than aesthetic pleasure and perhaps ritual, and that this signifies perhaps the earliest truly modern human behaviour. Yet, in 1925 a cave on the other side of South Africa, in Limpopo Province, yielded a striking example of a possible ‘collector’s piece’ from much earlier times. It is associated with remains of australopithecines and has been dated to around 3 Ma ago (see: Earliest sign of a sense of aesthetics, November 2020).

Source: Wilkins, J. et al.2021. Innovative Homo sapiens behaviours 105,000 years ago in a wetter Kalahari. Nature, v. 323 DOI: 10.1038/s41586-021-03419-0

Magnetic reversal and demise of the Neanderthals?

A rumour emerged last week that the Neanderthals met their end as one consequence of an extraterrestrial, possibly even extragalactic influence. Curiously, it stems from a recent discovery in New Zealand, where of course Neanderthals never set foot and nor did anatomically modern humans, the ancestors of Maori people, until a mere 800 years ago. It started with an ancient log from a kauri tree (Agathis australis), a species that Maoris revere. Found in excavations of boggy ground, the log weighed about 60 tons, so it was a valuable commodity, especially as it is illegal to fell living kauri trees. The wood is unaffected by burial and insect attack, has a regular grain and colour throughout, so is ideal for monumental Maori sculpture. Such swamp kauri also preserves their own life history in annual growth rings, and the log in question has 1700 of them. Using growth rings to chart climate variation gives the most detailed records of the recent past, provided the wood can be dated. Matching growth ring records from several trees of different ages is key to charting local climate with annual precision over several millennia.

An ancient kauri tree log recovered by swampland excavations in New Zealand. (Credit: Jonathan Palmer, in Voosen 2021)

Radiocarbon dating indicates that this particular kauri tree was growing around 42 thousand years ago. That is close to the upper limit for using 14C concentration in organic matter to determine age because the isotope has a short half-life (5730 years). In this case samples of the log would contain only about 0.7 % of its original complement of radioactive carbon. Cosmic rays generate 14C when they hit nitrogen atoms in the atmosphere and it enters COand thus the carbon cycle. Carbon dioxide taken up by photosynthesis to contribute carbon to plants contains only about one part per trillion of 14C. Consequently wood as ancient as that in the kauri log contains almost vanishingly small amounts, yet it can still be measured using mass spectrometry to yield an accurate radiometric age.

The particularly interesting thing about the 42 ka date is that it coincides with the timing of the last reversal of the Earth’s magnetic field, known as the Laschamps event. The kauri tree bears detailed witness through its growth rings to the environmental effects of a decrease in that field to almost zero as the poles flipped. The bulk of cosmic rays are normally deflected away from the Earth by the geomagnetic field, but during a reversal a great many more pass through the atmosphere, the most energetic reaching the surface and the biosphere. The kauri growth rings record fluctuations in the generation of 14C by their passage and thereby the geomagnetic field strength, which was only 6% of normal levels from 42.3 to 41.6 ka (Cooper, A. and 32 others  2021. A global environmental crisis 42,000 years ago. Science, v. 371, p. 811-818; DOI: 10.1126/science.abb8677). This coincided with an unrelated succession of periods of low solar activity and a reduced solar ‘wind’, which also provides some cosmic-rayprotection when activity is at normal levels; a ‘double whammy’. One consequence would have been destruction of stratospheric ozone by cosmic rays and thus increased ultraviolet exposure at ground level.

Combined with the highly precise growth-ring dating, the climatic changes over the 1700 year lifetime of the kauri tree can be linked to other records of environmental change. These include glacial ice- and lake-bed cores together with stalactite layers. Apparently, the Laschamps geomagnetic reversal coincided with abrupt shifts in wind belts and precipitation, perhaps triggering major droughts in the southern continents. Highly plausible, but some of the other speculations are less certain. For instance, some time around 42 ka, but far from well-established, Australia’s marsupial megafauna experienced major extinctions, the Neanderthals disappear from the fossil record and modern humans started decorating caves in Europe (20 ka after they did in Indonesia). In fact, speculation becomes somewhat silly, with suggestions that early Europeans went to live in caves because of increased exposure to UV (they knew, did they, while Neanderthals didn’t?), their painting and, by implication, their entire culture shifting through the shock and awe of mighty displays of the aurora borealis. Just because the number 42 is (or was), according to the late Douglas Adams’s Hitchhiker’s Guide to the Galaxy, ‘the answer to life, the universe and everything’, the authors tag the episode as the ‘Adams Event’. In their summary for The Conversation they include an animation with a quintessential Stephen Fry narrative, which Earth-logs readers can judge for themselves. Perhaps ‘Lockdown Trauma’ has a lot more to answer for, other than upsurges in Zoom conferences, knitting and gourmet experimentation …

See also: Voosen, P. 2021. Kauri trees mark magnetic flip 42,000 years ago. Science, v. 371, p. 766; DOI: 10.1126/science.371.6531.766

And here’s another snippet: Neanderthal link to our brain

Elizabeth Pennisi reports on a ‘Petri-dish’ experiment that substitutes a Neanderthal gene for a modern human one in a culture of human brain tissue. It gives some idea of how our very close relative may have thought differently from us. Pennisi, E. 2021. Neanderthal-inspired ‘minibrains’ hint at what makes modern humans specialScience, online news item; DOI:10.1126/science.abh0331

The ancestry of our opposable thumbs

Since the appearance of smart phones and the explosion of social media our thumbs have found a new niche; typing while holding a mobile. At a desktop keyboard, most of us don’t use thumbs very much, unless we have mastered fast touch typing, but for a huge variety of manual tasks thumbs are essential. The first makers of sophisticated stone tools must have been able to grip between fingers and thumb to manipulate the materials from which they were made and to perform the various stages in creating a razor sharp edge. To do that, as most of us are aware, the tip of the thumb must be capable of touching the tips of all four fingers; an opposable thumb is essential for the ‘precision grip’. Being able to tell when opposable thumbs evolve depends, of course, on finding hand-bone fossils. Being made of many bones disarticulated hands are a lot more fragile than long bones or those of the skull. Complete fossil hands are rare, as are feet, but a number have been found more or less complete. Whichever hominin had evolved opposable thumbs, their potential would have given them a considerable advantage over those that hadn’t.

The main muscles that control the movements of modern human fingers and thumb (Credit: Wikipedia)

Simply comparing the shapes of fossilised bones of fingers and thumbs with those of modern humans and other living primates has, so far, not proved capable of resolving with certainty which hominin groups either did or did not have opposable thumbs. The key lies in the muscles that operate them. It has become commonplace to reconstruct faces and even whole bodies from fairly complete skeletal remains by modelling musculature from the positioning and shape of the points of attachment of muscles to bone. But that become increasingly difficult for the small-scale and intricate attachments in hands. The critical muscle for opposable thumbs is known as the Opponens pollicis (the Latin for thumb is Digitus pollex); a small triangular muscle that operates in conjunction with three others (with pollicis in their Latin names).

Fotios Karakostis and six colleagues from German, Swiss and Greek universities have devised software that can model muscles in 3-D (F.A. Karakostis et al. 2021. Biomechanics of the human thumb and the evolution of dexterityCurrent Biology, v.31,  online; DOI: 10.1016/j.cub.2020.12.041). Based on the anatomy of human and chimpanzee hand muscles and the positions of their attachment to individual bones, they have been able to establish a series of parameters that clearly distinguish the morphological and probably functional characteristics of the thumbs of these living primates. Complete sets of thumb bones from four Neanderthal skeletons show that they were significantly, but only slightly, different from anatomically modern humans. Those from three species of Australopithecus (africanus, sediba and afarensis) lie between ours and chimps’, with significantly closer affinity to chimpanzees. It seems that australopithecines of whatever age were not equipped with opposable thumbs and were possible tool producers and users with the very limited capabilities of modern chimps; holding, pounding and poking. A single set of hominin thumb bones from about two million years ago that were found in the famous Swartkrans Cave in South Africa show just as close affinity in thumb opposability to humans as do Neanderthals. So at 2 Ma there was a hominin species sufficiently dextrous to make and use sophisticated tools. The problem is, the bones are not directly associated with others and have been ascribed by different authors either to H. habilis or Paranthropus robustus. Interestingly, this paranthropoid has also been suggested (controversially) to have been the first known hominin to use fire, and it also used digging sticks. No one has ever suggested that the genus Homo descended from a paranthropoid ancestor or vice versa; these massively jawed beings did coexist with early humans in East Africa for over a million years. The other hominin who left hands in the geological record was Homo naledi; a controversial species because it was found in a barely accessible cave chamber, and took a while to date. This context gave rise to the notions that it was the direct ancestor of humans and that it buried its dead in a special place. However, it turned out to be relative recent, at about 280 ka (see: Homo naledi: an anti-climax; May 2017). Homo naledi does seem to have had opposable thumbs, but there is no associated evidence to suggest either tool making or use.

Fascinating as the methodology outlined by Karakostis et al. is, their findings do not take early human capabilities very much further than what is already known. Tools were made and used as far back as 3.3 Ma ago, and we know that H. habilis was doing this by about 2.6 Ma; i.e. long before the first evidence for opposable thumbs, and who had them first is uncertain. What is clear is that sophisticated tools, such as the bifacial Acheulian artifacts whose manufacture demands great dexterity, only appeared after the potential for nimble dexterity (about 1.8 Ma). The same goes for the first migration out of Africa, at about the same time, which demanded resourcefulness that may have sprung from the ability to manipulate natural materials effectively and carefully

See also: Handwerk B. 2012. How dexterous thumbs may have helped shape evolution two million years ago. (Smithsonian Magazine, 28 January 2021); Bower, B. 2021. Humanlike thumb dexterity may date back as far as 2 million years ago. (Science News, 28 January 2021)

How like the Neanderthals are we?

An actor made-up to resemble a Neanderthal man in a business suit traveling on the London Underground. (Source: screen-grab from BBC2 Neanderthals – Meet Your Ancestors)

In the most basic, genetic sense, we were sufficiently alike for us to have interbred with them regularly and possibly wherever the two human groups met. As a result the genomes of all modern humans contain snips derived from Neanderthals (see: Everyone now has their Inner Neanderthal; February 2020). East Asian people also carry some Denisovan genes as do the original people of Australasia and the first Americans. Those very facts suggest that members of each group did not find individuals from others especially repellent as potential sexual partners! But that covers only a tiny part of what constitutes culture. There is archaeological evidence that Neanderthals and modern humans made similar tools. Both had the skills to make bi-faced ‘hand axes’ before they even met around 45 to 40 ka ago.  A cave (La Grotte des Fées) near Châtelperron to the west of the French Alps that was occupied by Neanderthals until about 40 ka yielded a selection of stone tools, including blades, known as the Châtelperronian culture, which indicates a major breakthrough in technology by their makers. It is sufficiently similar to the stone industry of anatomically modern humans (AMH) who, around that time, first migrated into Europe from the east (Aurignacian) to pose a conundrum: Did the Neanderthals copy Aurignacian techniques when they met AMH, or vice versa? Making blades by splitting large flint cores is achieved by striking the cores with just a couple of blows with a softer tool. At the very least Neanderthals had the intellectual capacity to learn this very difficult skill, but they may have invented it (see: Disputes in the cavern; June 2012). Then there is growing evidence for artistic abilities among Neanderthals, and even Homo erectus gets a look-in (see: Sophisticated Neanderthal art now established; February 2018).

Reconstructed burial of a Neanderthal individual at La Chappelle-aux-Saints (Credit: Musée de La Chapelle-aux-Saints, Corrèze, France)

For a long time, a pervasive aspect of AMH culture has been ritual. Indeed much early art may be have been bound up with ritualistic social practices, as it has been in historic times. A persuasive hint at Neanderthal ritual lies in the peculiar structures – dated at 177 ka – found far from the light of day in the Bruniquel Cave in south-western France (see: Breaking news: Cave structures made by Neanderthals; May 2016). They comprise circles fashioned from broken-off stalactites, and fires seem to have been lit in them. The most enduring rituals among anatomically modern humans have been those surrounding death: we bury our dead, thereby preserving them, in a variety of ways and ‘send them off’ with grave goods or even by burning them and putting the ashes in a pot. A Neanderthal skeleton (dated at 50 ka) found in a cave at La Chappelle-aux-Saints appears to have been buried and made safe from scavengers and erosion. There are even older Neanderthal graves (90 to 100 ka) at Quafzeh in Palestine and Shanidar in Iraq, where numerous individuals, including a mother and child, had been interred. Some are associated with possible grave goods, such as pieces of red ochre (hematite) pigment, animal body parts and even pollen that suggests flowers had been scattered on the remains. The possibility of deliberate offerings or tributes and even the notion of burial have met with scepticism among some palaeoanthropologists. One reason for the scientific caution is that many of the finds were excavated long before the rigour of modern archaeological protocols

Recently a multidisciplinary team involving scientists from France, Belgium, Italy, Germany, Spain and Denmark exhaustively analysed the context and remains of a Neanderthal child found in the La Ferrassie cave (Dordogne region of France) in the early 1970s  (Balzeau, A. and 13 others 2020. Pluridisciplinary evidence for burial for the La Ferrassie 8 Neandertal childScientific Reports, v. 10, article 21230; DOI: 10.1038/s41598-020-77611-z). Estimated to have been about 2 years old, the child is anatomically complete. Bones of other animals found in the same deposit were less-well preserved than those of the child, adding weight to the hypothesis that a body, rather than bones, had been buried soon after death. Luminescence dating of the sediments enveloping the skeleton is considerably older than the radiocarbon age of one of the child’s bones. That is difficult to explain other than by deliberate burial. It is almost certain that a pit had been dug and the child placed in it, to be covered in sediment. The skeleton was oriented E-W, with the head towards the east. Remarkably, other Neanderthal remains at the La Ferrassie site also have heads to the east of the rest of their bones, suggesting perhaps a common practice of orientation relative to sunrise and sunset.

It is slowly dawning on palaeoanthropologists that Neanderthal culture and cognitive capacity were not greatly different from those of anatomically modern humans. That similar beings to ourselves disappeared from the archaeological record within a few thousand years of the first appearance of AMH in Europe has long been attributed to what can be summarised as the Neanderthals being ‘second best’ in many ways. That may not have been the case. Since the last glaciation something similar has happened twice in Europe, which analysis of ancient DNA has documented in far more detail than the disappearance of the Neanderthals. Mesolithic hunter-gatherers were followed by early Neolithic farmers with genetic affinities to living people in Northern Anatolia in Turkey – the region where growing crops began. The DNA record from human remains with Neolithic ages shows no sign of genomes with a clear Mesolithic signature, yet some of the genetic features of these hunter-gatherers still remain in the genomes of modern Europeans. Similarly, ancient DNA recovered from Bronze Age human bones suggests almost complete replacement of the Neolithic inhabitants by people who introduced metallurgy, a horse-centred culture and a new kind of ceramic – the Bell Beaker. This genetic group is known as the Yamnaya, whose origins lie in the steppe of modern Ukraine and European Russia. In this Neolithic-Bronze Age population transition the earlier genomes disappear from the ancient DNA record. Yet Europeans still carry traces of that earlier genetic heritage. The explanation now accepted by both geneticists and archaeologists is that both events involved assimilation and merging through interbreeding. That seems just as applicable to the ‘disappearance’ of the Neanderthals

See also: Neanderthals buried their dead: New evidence (Science Daily, 9 December 2020)

Doggerland and the Storegga tsunami

Britain is only an island when sea level stands high; i.e. during interglacial conditions. Since the last ice age global sea level have risen by about 130 m as the great northern ice sheets slowly melted. That Britain could oscillate between being part of Europe and a large archipelago as a result of major climatic cycles dates back only to between 450 and 240 ka ago. Previously it was a permanent part of what is now Europe, as befits its geological identity, joined to it by a low ridge buttressed by Chalk across the Dover Strait/Pas de Calais. All that remains of that are the white cliffs on either side. The drainage of what became the Thames, Seine and Rhine passed to the Atlantic in a much larger rive system that flowed down the axis of the Channel. Each time an ice age ended the ridge acted as a dam for glacial meltwater to form a large lake in what is now the southern North Sea. While continuous glaciers across the northern North Sea persisted the lake remained, but erosion during interglacials steadily wore down the ridge. About 450 ka ago it was low enough for this pro-glacial lake to spill across it in a catastrophic flood that began the separation. Several repeats occurred until the ridge was finally breached (See: When Britain first left Europe; September 2007). Yet sufficient remained that the link reappeared when sea level fell. What remains at present is a system of shallows and sandbanks, the largest of which is the Dogger Bank roughly halfway between Newcastle and Denmark. Consequently the swamps and river systems that immediately followed the last ice age have become known collectively as Doggerland.

The shrinkage of Doggerland since 16,000 BCE (Credit: Europe’s Lost Frontiers Project, University of Bradford)

Dredging of the southern North Sea for sand and gravel frequently brings both the bones of land mammals and the tools of Stone Age hunters to light – one fossil was a skull fragment of a Neanderthal. At the end of the Younger Dryas (~11.7 ka) Doggerland was populated and became a route for Mesolithic hunter-gatherers to cross from Europe to Britain and become transient and then permanent inhabitants. Melting of the northern ice sheets was slow and so was the pace of sea-level rise. A continuous passage across Dogger Land  remained even as it shrank. Only when the sea surface reached about 20 m below its current level was the land corridor breached bay what is now the Dover Strait, although low islands, including the Dogger Bank, littered the growing seaway. A new study examines the fate of Doggerland and its people during its final stage (Walker, J. et al. 2020. A great wave: the Storegga tsunami and the end of Doggerland? Antiquity, v. 94, p. 1409-1425; DOI: 10.15184/aqy.2020.49).

James Walker and colleagues at the University of Bradford, UK, and co-workers from the universities of Tartu, Estonia, Wales Trinity Saint David and St Andrews, UK, focus on one devastating event during Doggerland’s slow shrinkage and inundation. This took place around 8.2 ka ago, during the collapse of a section of the Norwegian continental edge. Known as the Storegga Slides (storegga means great edge in Norse), three submarine debris flows shifted 3500 km3 of sediment to blanket 80 thousand km2 of the Norwegian Sea floor, reaching more than half way to Iceland.  Tsunami deposits related to these events occur along the coast western Norway, on the Shetlands and the shoreline of eastern Scotland. They lie between 3 and 20 m above modern sea level, but allowing for the lower sea level at the time the ‘run-up’ probably reached as high as 35 m: more than the maximum of both the 26 December 2004 Indian Ocean tsunami and that in NW Japan on 11 March 2011. Two Mesolithic archaeological sites definitely lie beneath the tsunami deposit, one close to the source of the slid, another near Inverness, Scotland. At the time part of the Dogger Bank still lay above the sea, as did a wide coastal plain and offshore islands along England’s east coast. This catastrophic event was a little later than a sudden cooling event in the Northern Hemisphere. Any Mesolithic people living on what was left of Doggerland would not have survived. But quite possibly they may already have left as the climate cooled substantially

A seabed drilling programme financed by the EU targeted what lies beneath more recent sediments on the Dogger Bank and off the embayment known as The Wash of Eastern England. Some of the cores contain tsunamis deposits, one having been analysed in detail in a separate paper (Gaffney, V. and 24 others 2020. Multi-Proxy Characterisation of the Storegga Tsunami and Its Impact on the Early Holocene Landscapes of the Southern North Sea. Geosciences, v. 10, online; DOI: 10.3390/geosciences10070270). The tsunami washed across an estuarine mudflat into an area of meadowland with oak and hazel woodland, which may have absorbed much of its energy. Environmental DNA analysis suggests that this relic of Doggerland was roamed by bear, wild boar and ruminants. The authors also found evidence that the tsunamis had been guided by pre-existing topography, such as the river channel of what is now the River Great Ouse. Yet they found no evidence of human occupation. Together with other researchers, the University of Bradford’s Lost Frontiers Project have produced sufficient detail about Doggerland to contemplate looking for Mesolithic sites in the excavations for offshore wind farms.

See also: Addley, E. 2020.  Study finds indications of life on Doggerland after devastating tsunamis. (The Guardian, 1 December 2020); Europe’s Lost Frontiers website