Comparison of different tool industries of the Upper Palaeolithic. a–c Aurignacian: prismatic core (a: length approx. 46 mm), retouched blade (b: length approx. 95 mm) and retouched bladelet (c: length approx. 31 mm), from Cosava, Romania; d–f Châtelperronian: points (d: length approx. 64 mm), perforated animal teeth (‘pendants’) (e: greatest length approx. 46 mm) and bone artifact (f: length approx. 112 mm), from the Grotte du Renne, Arcy-sur-Cure, France; g, h Gravettian: backed bladelet (g: length approx. 30 mm) and prismatic core (h: length approx. 42 mm) from Bistricioara-La Mal, Romania.
The Châtelperronian culture was first identified at a site in Auvergne in central France. It gained notoriety thanks to André Leroi-Gourhan, one of the grand figures in the history of French archaeology. Leroi-Gourhan was instrumental in preserving some of the treasures of the Louvre during the Second World War. He also pioneered large-scale horizontal excavations of prehistoric sites, in order to reveal activity areas and site organization rather than focusing on stratigraphy. From 1949 to 1963 he excavated at the Grotte du Renne, a cave at Arcy-sur-Cure in Burgundy. The stone tools he found, like the Uluzzian, seemed to be intermediate between Mousterian and Aurignacian types. Blades predominated, with extensive retouching on a long, curved surface that was intentionally dulled, presumably so it could be held in the hand for cutting. These were probably made with soft-hammer percussion, making the Châtelperronian an Upper Palaeolithic industry.
Leroi-Gourhan also found ivory ornaments and pierced teeth at the Grotte du Renne. These artifacts were symbolic and were unlike anything that had been associated with the Neanderthals. Yet Leroi-Gourhan uncovered Neanderthal teeth within the Châtelperronian layers. These indicated that something extraordinary was happening here. Specialists such as François Bordes and Paul Mellars argued that Châtelperronian stone tools evolved out of a local Mousterian tool variant, the Mousterian of Acheulian Tradition (which was the one Mousterian variant that Bordes considered to be chronologically restricted and late in the sequence). The ornamental ivory and teeth seemed crudely made, as if by humans who had seen jewelry but who were unskilled at its manufacture and may not have fully understood its purpose. In 1979 this line of argument received a huge boost in the form of a Neanderthal skeleton unearthed among Châtelperronian artifacts at Saint-Césaire, near the Atlantic coast. At the same time, the Saint-Césaire skeleton (see p. 141) helped put to rest another theory, which was that Neanderthals evolved into modern humans in Europe. The presence of a ‘classic’ Neanderthal skeleton from just 40,000 years ago among Upper Palaeolithic tools was strong evidence that modern humans were intrusive and evolutionarily separate from Neanderthals.
Today the tide is turning once again. Re-dating of the Châtelperronian layers at the Grotte du Renne using ultrafiltration has shown evidence of mixing, with material as old as 49,000 years ago (before the start of the Châtelperronian) and as young as 21,000 years ago (after the extinction of the Neanderthals). Researchers are also questioning the association of the Saint-Cßsaire Neanderthal and Châtelperronian tools. It now seems that the skeleton is in a mixed layer not unlike the ‘Transitional Middle/Upper Palaeolithic’ layers in Greece, casting doubt on its very late date. A further blow to the acculturation argument is that stone tool experts such as Jean-Guillaume Bordes (no relation to François) are now questioning whether the Châtelperronian evolved from the Mousterian.
Drawing of the skull of a ‘classic’ Neanderthal found at Saint-Césaire, dated to around 40,000 years ago (left) and the skull and mandible (not from the same individual) of an Upper Palaeolithic modern human unearthed in the Czech Republic.
Officially archaeologists now say that the association between the Châtelperronian and the Neanderthals is unclear. Unofficially there is growing doubt about the association and many now see the Châtelperronian in central and south-western France as simply a regional variant of the Upper Palaeolithic industries brought to Europe by modern humans. Still others remain convinced that the Châtelperronian is a Neanderthal industry.
If the Châtelperronian turns out to have been a modern human industry, is this an argument against Neanderthal cognitive abilities? Yes and no. While the Châtelperronian was once seen as a Neanderthal ‘acculturation’ to the Upper Palaeolithic, it was always seen as inferior to the neighbouring Aurignacian tradition. It had defined the limits of what Neanderthals could achieve. If we now accept that there is no solid evidence for Neanderthal use of Upper Palaeolithic technology, we can no longer say that the Neanderthals could only effect a poor imitation of the Aurignacian. Instead, we are left with a picture of the Neanderthals simply coexisting near modern humans who arrived in their lands. This leaves us wondering, if the Châtelperronian is a modern human industry, would it have always been considered ‘inferior’ to the Aurignacian?
Can we blame the Neanderthals’ extinction on the modern human pioneers entering Europe? In the first edition of this book we suggested not, but in light of changes in dating technology, our view has changed substantially. At this point, with lingering uncertainties about radiometric dates, the evidence is strong but the case is not proven. In many areas, such as the Caucasus Mountains, southeastern Europe and parts of Italy, Homo sapiens entered territory that had been vacated by Neanderthals. In other territories, such as France, southern Germany and northern Spain, we have a picture of two separate populations living side-by-side with possible localized acculturation.
As this process unfolded, the Phlegraean Fields volcano in Italy erupted 39,000 years ago (see pp. 166–67). Evidence for the continuing survival of the Neanderthals after that time is controversial. But they were not the only humans to disappear around then. The Châtelperronian and Uluzzian traditions, both possibly modern human, ended along with the Mousterian. The Aurignacian would not last much longer. A new modern human culture, the Gravettian, would soon sweep across Europe.
Cracking the DNA code
As we have seen, Neanderthal bones contain an enormous library of information. Their shape and thickness can tell us about Neanderthal bodies and also hint at evolutionary connections with other hominin species. The ratio of the unstable carbon isotope 14C to the stable isotope 12C can tell us how long ago the individual died. And the ratio of stable carbon and nitrogen isotopes can tell us what the individual ate.
The impact of volcanoes
Some time between about 71,000 and 75,000 years ago a supervolcano on Mt Toba on the island of Sumatra, Indonesia, erupted in perhaps the most massive explosion the world has experienced during the whole course of human evolution since the genus Homo first appeared in Africa. The Toba eruption had effects that were far-reaching, both geographically and through time. Closer to the Neanderthals’ home, and to the crucial millennia around their extinction, an eruption near Naples at the Phlegraean Fields 39,000 years ago was not quite as big but could well have triggered a ‘volcanic winter’ that lasted many years.
Could these two volcanic events have been the true culprits behind the extinction of the Neanderthals, with Homo sapiens no more than opportunists who swept in afterwards? The Toba super-eruption ejected as much as 3,000 cubic kilometres (700 cu. miles) of magma. Debris has been identified as far away as India. It is likely that most mammals and birds within 350 kilometres (200 miles) of the eruption would have been instantly destroyed. Global temperatures dipped for several years and the effect lasted a few hundred years. What was the consequence of this for humans?
Indonesia is far from the centres of human life in this period. Neanderthals were restricted to Europe and western Asia, and modern humans were just starting – or just about to start – their major exodus from Africa. The island of Flores, where the dwarf-like Homo floresiensis has been found, was outside the 350-kilometre kill zone, but would nevertheless have been under extreme stress.
The Oxford archaeologist Michael Petraglia, working at Jwalapuram in India, has argued for continuity in stone tool manufacture before and after the Toba eruption. The intriguing question about th
e tools – and Petraglia has found only a few hundred artifacts both above and below the Toba ash line at Jwalapuram – is who made them. He believes they were made by modern humans, while others, citing genetic evidence, believe that modern humans did not leave Africa until later.
The mystery of the Indian Middle Palaeolithic highlights the fact that the various hominin species in Asia all used similar stone technology in this period, making it hard to separate Neanderthals, Denisovans and modern humans in the absence of human remains. In any case, it seems whoever was making stone tools in India around the time of the Toba eruption survived the ordeal.
When most of us think of volcanoes near Naples, Italy, we think of Mt Vesuvius, which buried the Roman city of Pompeii. Some 20 kilometres (12 miles) further west along the coast is the Bay of Pozzuoli, which comprises part of another caldera. It is this volcano, known as the Phlegraean Fields, that erupted 39,000 years ago, when modern humans were already established in Europe and the Neanderthals’ fate was uncertain. This eruption threw out 250 cubic kilometres (60 cu. miles) of magma, a fraction of the size of the Toba super-eruption, yet ash from the volcano – detectable only through microscopic particles of glass showing the chemical signature of the event – reached Asia.
Satellite view of Lake Toba, Indonesia, the remains of a supervolcano that erupted at some point between 71,000 and 75,000 years ago, possibly the largest volcanic eruption since the dawn of humanity. Could this or a smaller eruption at the Phlegrean Fields, near Naples, Italy, 39,000 years ago, have played a part in the extinction of the Neanderthals?
In the years around the Phlegraean Fields’ eruption a large number of icebergs entered the north Atlantic, cooling global temperatures in what is known as a Heinrich event. This was a difficult time, to be sure.
The evidence of these two volcanic events serves as a worrying reminder of the fragility of our environment. The second of these eruptions took place when the Neanderthals were vulnerable, as modern humans had already encroached on their former territories. It is possible that it could have been the final blow, quickening a process that was long underway. We know that modern humans survived the blast, thereby showing a degree of resiliency the Neanderthals may have lacked.
There is one more piece of information contained within some Neanderthal bones, and this is the hardest to identify from among possible contaminants, for it is a structure common to all living things. DNA is the building block of life; it contains the genes that define an individual or a species. Some Neanderthal bones still carry Neanderthal DNA. Getting to it, however, is far from easy. The people who excavate and analyse Neanderthal bones have DNA that is extremely similar. Bacteria that live in the bones also have DNA.
Researchers at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, led by Svante Pääbo, have found ways around these problems to produce a draft, and subsequently a high-resolution Neanderthal genome. What does this ancient DNA tell us about the relationship between Neanderthals and modern humans? What can we say about possible interbreeding?
Preliminary answers to these questions started to appear in the late 1990s with the recovery of mitochondrial DNA (mtDNA) from the original bones found in the Neander Valley back in 1856. Mitochondrial DNA is easier to recover and sequence because it is much smaller than nuclear DNA. It is passed through the maternal line and is believed to mutate at a constant rate, making it possible to calculate the time since two individuals shared a common ancestor. The drawback of mtDNA is that it can only look back along one particular line, much like tracing genealogy only through last names which are passed down the paternal line, thus excluding information from other direct ancestors.
In 2008 headlines heralded some key results arising from the study of Neanderthal mtDNA recovered from eleven Neanderthal individuals from the Neander Valley (Germany), Mezmaiskaya Cave (Russia), Vindija (Croatia), Engis and Scladina (Belgium), La Chapelle-aux-Saints and Rochers de Villeneuve (France), Monte Lessini (Italy) and El Sidrón (Spain). According to this line of evidence, Neanderthals and modern humans last shared a common ancestor around 500,000 years ago. This seemed to reinforce the fossil evidence, which indicated that the two populations evolved out of Homo heidelbergensis around that time. It also suggested that there was no subsequent interbreeding between the species.
Just as these results came out, the picture began to change dramatically. Thanks to two technological developments, the recovery of Neanderthal DNA was proceeding apace. Polymerase chain reaction (PCR) was developed in the 1980s as a way to amplify the signal of a limited amount of DNA and make possible the analysis of small degraded fragments from ancient bones. And high-throughput sequencing was developed by the company 454 Life Sciences, founded in 1999 in Branford, Connecticut, making it economical in terms of time and money to produce a draft genome.
A draft Neanderthal genome was indeed published in 2010 in the periodical Science, but with it came a shock announcement. Based on samples extracted from three bones from three different individuals from Vindija, Pääbo and his team argued that there was, in fact, interbreeding between the two populations. They went further and said that modern human populations not indigenous to Africa show 1–4 per cent intrusive Neanderthal DNA in their genomes (this figure has since fallen closer to 2 per cent), while Neanderthals did not show intrusive DNA from Homo sapiens. It seems that modern Europeans do not have any more Neanderthal DNA within them than do Aboriginal Australians. This implies that the genes have recorded interbreeding events that took place at the early stages of the out-of-Africa expansion, before modern humans reached Europe or Australia. It has not taken long for this discovery to be commercialized. At least one company now offers a Neanderthal DNA percentage test for a few hundred dollars.
A more detailed picture of the interbreeding between Neanderthals and modern humans emerged with the sequencing of a high-resolution genome from the femur of a modern human individual who lived in Siberia 45,000 years ago. This is the first case in which DNA has been retrieved from an early modern human – itself a breakthrough in ancient DNA studies. This modern human does not have more Neanderthal DNA than present-day humans, but the Neanderthal DNA that he has is preserved in bigger chunks. This allows researchers to pinpoint the timing of the interbreeding to between 50,000 and 60,000 years ago. There may have been more recent interbreeding events between the two populations, but their effect was less significant. Equally, potential interbreeding events between Neanderthals and modern humans who lived in the Middle East around 100,000 years ago do not seem to have made any lasting impression on the genome of present-day humans. A partially preserved modern human skull found in Manot Cave in northern Israel, dating from around 55,000 years ago, may be representative of the modern human populations that interbred with Neanderthals after the dispersal out of Africa and before expanding across Eurasia.
The DNA revelation – that the Neanderthals live on, in some senses, in the blood of up to six billion living people – was just one striking aspect of an ongoing series of discoveries from the Neanderthal genome. It has also emerged that Neanderthals share modern human genes for green eyes and red hair. As many had predicted, given their evolution in Europe, the Neanderthals seem to have evolved genes for pale skin independently from modern Caucasians. They also had a gene called FOXP2, which is the same as it appears in modern humans. FOXP2, initially heralded as ‘the language gene’, is related to the fine motor skills, coordination and executive function required for producing complex sounds for speech and, presumably, also for making complex stone tools. This implies that both species inherited FOXP2 from our common ancestor, Homo heidelbergensis.
What kind of DNA have we inherited from the Neanderthals? Clearly it is not related to our modern human skeletal structure. Decoding DNA and identifying the function of particular genes is still a young science. There are some preliminary indications, however, and these can be categorized into three groups: helpful, unhelpful and mysterious. What seems helpful is that
non-Africans have inherited some genes related to their immune system from Neanderthals. Since these have not been selected out, they probably bestow some as-yet unidentified protection against disease. The most unhelpful inheritance is a gene that heightens the risk of type 2 diabetes, particularly for Asians and Native Americans. It is likely that Neanderthals developed this trait to cope with frequent periods of near-starvation, and it has only become a big problem since the development of agriculture and the spread of the western diet. Some genes related to skin and hair may have endured thanks to protections they offer against the cold or perhaps for sexual selection. Aside from some slightly more arcane traits, a great deal of the surviving Neanderthal DNA remains a mystery.
In addition to the Neanderthals, DNA sequencing has provided evidence for other cases of interbreeding with archaic human populations. For example, Denisovans, whose DNA has been extracted from a finger bone found in a Siberian cave from before the arrival of modern humans, seem to live on as a small percentage of the DNA of some modern Asian populations. The Denisovans represent the only human population known simply from their DNA. We do not even know how their appearance may have differed from ours or from that of the Neanderthals. A study of mtDNA links the Denisovans with the incipient Neanderthals of Sima de los Huesos (see pp. 55–59), suggesting a recent common ancestry between Denisovans and Neanderthals, or at least some form of genetic exchange. There also seems to have been an interbreeding event within Africa with an unidentified archaic population less than 50,000 years ago. The more we learn about DNA, the murkier and more interesting the past hundred thousand years become.
The Neanderthals Rediscovered: How Modern Science is Rewriting Their Story Page 15
