We are left with a picture of a modern world population that is very homogeneous compared with other species. Homo sapiens has a recent African origin. Yet we seem occasionally to have interbred with other related populations, such as the Neanderthals, and carry around their genes at low levels. As DNA science matures, we look forward to getting a clearer picture of how this played out and to filling the gaps in the sparse record of human remains.
The study of ancient DNA is likely to tell us far more about the Neanderthals than their history of interbreeding. According to Stringer, ‘genomic work will lead the way, once we can achieve high quality reconstructed Neanderthal genomes to compare with those of chimps, humans and Denisovans. We will start to tease out features that typify each lineage, and at least make a start in looking at possible differences in brain function.’
One other notable discovery identified in Neanderthal genes is that their genetic diversity was contracting around 50,000 years ago. There was also inbreeding. A high-quality genome from the toe bone of a Neanderthal woman from Denisova Cave in Siberia revealed that in several parts of her genome the two strands of her DNA were identical. Her parents must have been closely related, maybe even half-siblings. Inbreeding was also common among her recent ancestors, usually a sign of small groups living in relative isolation. To find out whether inbreeding was common among other Neanderthal populations, we will have to wait for further high-quality Neanderthal genome sequences. Nevertheless, Neanderthals and Denisovans have far less genetic variation than present-day modern humans have, even outside Africa. This confirms the archaeological observation that Neanderthals responded to climate stress by declining in overall numbers and dying out completely in some peripheral areas. To explore the circumstances around their final disappearance, we now turn our attention back to Europe and see what role climate might have played in the Neanderthals’ demise.
Exit, Stage 3
What was the climate of Europe like during these eventful years? Could a glacial period explain the Neanderthals’ disappearance?
These questions were at the heart of a major interdisciplinary research initiative called the Stage 3 Project, which was the brainchild of Sir Nicholas Shackleton and Tjeerd van Andel at Cambridge. Stage 3 refers to the geological period from 60,000 to 24,000 years ago, when the ratio of oxygen isotopes, measured in deep-sea cores, indicates an interglacial or warm period. Stage 2 included the Last Glacial Maximum, popularly known as the peak of the Ice Age, and we currently live in Stage 1, an interglacial known as the Holocene.
Stage 3 was not nearly as warm and stable as Stage 1 (which started between 11,000 and 12,000 years ago), or as the Eemian (130,000 to 120,000 years ago), which we discussed in the previous chapter and which took place during Stage 5. Instead, Stage 3 was incredibly variable, which was itself a major source of stress. Temperatures fluctuated between warm and cold, with some cycles as short as 1,000 years. During the warm periods the climate would have been quite mild. For example, 45,000 years ago the mean temperature in July in north-eastern France is estimated to have been between 16°C and 22°C (61–72°F). Today that number is around 20°C (68°F).
Climate records show that northern Europe remained habitable during most of Stage 3. The lowlands of Scandinavia were not covered by glaciers until as late as 26,000 years ago. The persistence of warm conditions points away from cold climate alone as the cause of the Neanderthals’ extinction, as their numbers had gone down well before the climate reached its most challenging state.
One way to investigate the effect of the fluctuating climate on the Neanderthals is to look at its impact on other animals. Many large mammals, such as reindeer, horse, steppe rhinoceros and mammoth, as well as smaller species, such as the wolverine, wolf and fox, all survived Stage 3 and were present during the Last Glacial Maximum. Mammals that did not survive in Europe include the leopard, certain species of weasel and marten, and large species such as Merck’s rhinoceros and the straight-tusked elephant. There are intriguing parallels in the patterns of retreat and extinction between the Merck’s rhinoceros, straight-tusked elephant and the Neanderthals. It could be that the Neanderthal population was shrinking along with their preferred habitat.
A key trend towards the end of Stage 3 is the expansion of open steppe grasslands. One model of Neanderthal extinction, put forward by Clive Finlayson, who excavated Gorham’s Cave, is that the Gravettian culture was the first to exploit this environment. Finlayson argues that Homo sapiens, like wolves and bears, were better adapted to the pursuit hunting that led to success on the treeless tundras of Eurasia. Pursuit hunting involves long endurance running after prey, which can eventually give up in exhaustion. In contrast, Neanderthals stuck to rivers and the forest edges, where they could continue the kind of ambush hunting they had perfected over hundreds of thousands of years. Intriguingly, the first modern humans to reach Europe, who were part of the Aurignacian culture, followed the Neanderthals in preferring warmer, more sheltered areas. As the steppes expanded, Finlayson argues, modern humans of the Gravettian culture expanded, while the Neanderthals (and modern humans of the Aurignacian culture) contracted along with their preferred habitat. This pattern may have held for the Neanderthals in previous eras when the steppes expanded. But this time there was one crucial difference: they had company.
The Gravettian culture first appeared in the Danube corridor as early as 37,000 years ago. This was the start of a gradual cooling that, according to the Stage 3 Project, led to acute stress on the environment despite temperatures not yet reaching extremes. At this point the expansion of the grasslands was pronounced in northern Europe, but did not penetrate throughout France. Hilly areas with protected valleys, such as the Dordogne where many Neanderthal (and also Châtelperronian) sites are found, would have retained trees. By 25,000 years ago the Gravettian culture had spread to most of Europe including Britain, Spain, Portugal, Italy, Greece, much of eastern Europe and deep into Russia. At this late date the Neanderthals and the Mousterian culture were gone, and the Aurignacian culture had probably also disappeared.
What is the Gravettian culture? It is defined archaeologically by the appearance of certain tool types, a novel form of flint blade and bone points. But what really distinguished it from the Mousterian and Aurignacian cultures was that its population was much denser, with more sites in an area, that it reached a wider range of environments, notably the chilly plains of northern Europe, and that it had long-term settlements and food-storage capacity. The Gravettian is known particularly for its ‘Venus’ figurines, with exaggerated female forms. Unlike the meat-dependent Neanderthals of Europe, the culture involved river fishing. They had also learned to hunt the seasonal migrating animals of the steppes, in contrast to the more sedentary animals favoured by Neanderthals. It is important to note that some Homo sapiens using Aurignacian technology may well have been the first to develop the Gravettian industry. In other words the Gravettians may have represented an influx of new people from the Asian steppes or they may simply have been Aurignacians who developed new technologies.
Even before the first modern humans appeared in Europe, the Neanderthals had been in a stage of contraction. Why this happened is not entirely clear. It is probably a pattern that had happened many times to the Neanderthals and their ancestors over 500,000 years. They would contract to refugia and then re-expand. While the Aurignacian culture’s arrival and subsequent volcanic eruption may have been too big a stress for the Neanderthals, the Gravettians’ arrival was a game-changer. Here was a modern human group actually expanding during a cooling phase.
We turn now to the Iberian Peninsula, the area that many have argued could have been the Neanderthals’ final refuge in Europe. In Asia, the pattern of extinction is less clear, and it is likely that the number of Neanderthals there was never substantial, even as they moved eastward. Iberia, as we have seen, is a special case. It has a different environment from France, Germany and the Danube corridor, and is protected somewhat by the barrier of the Pyre
nees. On the Spanish side of the mountains is the Ebro River, historically a major geopolitical boundary. João Zilhão has argued that the ‘Ebro frontier’ approximates a line modern humans did not cross until relatively late.
A ‘Venus’ figurine from Dolni Vestonice, Czech Republic, made of fired clay and dating from the Gravettian period.
The skeleton of a child found at Lagar Velho, Portugal, is at the centre of the debate as to whether humans and Neanderthals interbred in Europe in the millennia just preceding the Neanderthals’ extinction.
By the time the Aurignacian culture gave way to the Gravettian culture in Europe, this line was breached. The question whether the Neanderthals lived even that long is now the subject of debate over dates. Some argue for very late Neanderthals less than 30,000 years ago in Gibraltar, others see around 35,000 years ago as closer to the last reliable date for a Neanderthal presence south of the Ebro River, while others still see no reliable evidence for either a late survival of the Neanderthals or a late arrival of modern humans in this region.
A study in 2013 tried to resolve this by re-dating bones from eleven sites in southern Iberia using ultrafiltration. Unfortunately, bone preservation in the area, as elsewhere in Mediterranean Europe, is poor, and only two sites provided material suitable for dating. These new dates turned out to be much earlier, between 50,000 and 45,000 years ago. Therefore there is a gap in reliable dates of the 40,000–30,000-year period in Iberia south of the Ebro River, which may be due to poor bone preservation alone, or to the absence of Neanderthals or modern humans or both populations from this region. Southern Iberia may have been a last refuge for the Neanderthals in Europe or may have been depleted of Neanderthals by 40,000 years ago, as were probably Crimea and the southern Balkans.
As to what possible interactions there may have been between the moderns and Neanderthals in the final days, there is a tantalizing site in Portugal. The remains of a four-year-old child were discovered in 1998 in a Gravettian rock shelter called Lagar Velho in the Lapedo Valley, about 150 kilometres (90 miles) north of Lisbon. Dating to 27,000 years ago, the so-called Lapedo child was buried with a pierced shell, the calling card of Homo sapiens for the previous 100,000 years, as well as with red ochre. Its body is clearly modern human. But Zilhão and the American anthropologist Erik Trinkaus argue that it also has Neanderthal traits which indicate a mixed ancestry.
Other specialists, such as Chris Stringer and Ian Tattersall, dispute this conclusion and see the Lapedo child simply as a modern human with no apparent recent Neanderthal admixture. There have been moments when this debate has been quite heated. This makes Lagar Velho the perfect place to end our story, as it reminds us that for all we have come to know about the Neanderthals, so much remains in dispute.
For Trinkaus and Zilhão the Neanderthals did not become extinct but were gradually absorbed into the intrusive modern human population. For Stringer and Tattersall, however, modern humans took over Europe from the Neanderthals, who became extinct. They have recently used the term ‘leaky replacement’ to account for the DNA evidence for limited interbreeding. In a sense the argument has now become one of degrees, as one side claims that Homo sapiens replaced Neanderthals with minor interbreeding (probably in western Asia soon after the African exodus, around 50,000–60,000 years ago) and the other side, citing possible hybrids such as the Lapedo child and Oase Cave skulls, claims more widespread population mixing.
Why have the stakes in this argument been so high and the debate so heated? While part of it is professional pride among palaeoanthropologists who disagree, part of it must be the implications for the Neanderthals’ humanity. For some it seems to be a continuation of the age-old debate over whether the Neanderthals were fully human or represent an inferior line. For example, ambivalence about Neanderthal humanity was on display in the title of Discover magazine’s tongue-in-cheek 2011 cover story reporting the Neanderthal and Denisovan DNA admixture news, which was ‘You Are Not Human’.
Our perspective, looking at the Neanderthals not as a snapshot in time but through the entire arc of their existence, is that they were on essentially the same trajectory as our species. Descended from Homo heidelbergensis, they became expert hunters. They developed Levallois stone tools, which required a higher degree of forward planning than the handaxes of their forebears. They survived in harsh climates by developing clothing and fire. They buried their dead and cared for the sick. They exploited a range of food resources including from the sea. They used red ochre and eagle talons, possibly for symbolic purposes. They had language. They expanded their homeland to the Near East, Central Asia and Siberia and survived in harsh northern latitudes.
All these accomplishments put the Neanderthals on a par with Homo sapiens from the Eemian interglacial, 120,000 years ago. When the two species first came together in Asia, it was the Neanderthals who had the upper hand. And when modern humans with the Aurignacian industry appeared in the Neanderthal homeland of Europe, the two species seemed to coexist even as they preferred the same habitats.
Many of the Neanderthals’ greatest advances occurred in Stage 3, less than 60,000 years ago. Their use of burial increased, which explains the large number of Neanderthal bones from this period. They increased the distance that they transported stone to make tools. Clive Finlayson and others argue that they were using feathers from birds such as eagles, vultures and falcons for ornamentation. They created a ‘hashtag’ pattern in Gorham’s Cave. And there is tantalizing evidence uncovered by Zilhão in Spain that in addition to using red ochre they were experimenting with a wider range of colours and had started to perforate and decorate shells. It is not possible to say what the Neanderthals might have achieved if they had had another 100,000 years to catch up.
Only when modern humans from the Gravettian culture figured out a way to vastly increase their numbers and their range of environments and resources can we say beyond any debate that the Neanderthal population had crashed to zero. It is possible that the first wave of modern humans to enter Europe suffered the same fate. Can we say that any of these groups was less than fully human?
Human history is filled with instances of people being overwhelmed by an intruding population. In some ways this has been part of the human condition. In these cases there have often been low (and at times substantial) levels of interbreeding between native and colonizer. In historical instances where both populations are clearly the same species, it is racist to attribute one side’s defeat to their biology.
In the Neanderthal case their biology truly was different. They were stronger, perhaps required a little more food to sustain themselves and their brains may have had smaller frontal cortices. They matured more quickly. Their brains retained the shape that our brains have at birth, and theirs were probably wired differently. Different need not mean inferior. Are we prepared to accept a different mind as a human mind? Did any of this mean they lacked the potential to thrive as we have?
One thing that all sides can agree with is that the Neanderthal way of life and body type did not survive. Whether they could have survived is something best left to our imaginations, which is where we turn in Chapter Seven.
CHAPTER seven
Still With Us?
‘Neanderthals are among us, even now!’ That’s the slogan on a T-shirt we once purchased from a certain ‘Saul Leviticus’ at an address he dubbed Neanderthal Central Control. The species may be extinct, but there remains some truth in the slogan. Neanderthals are not entirely gone. If anything, they are becoming ever more prevalent. From a rock band to popular novels, cult movies and scientific reconstructions, Neanderthals are hard to miss. But the author of the T-shirt was probably not thinking metaphorically.
Long before the DNA investigations, people like Mr Leviticus, and indeed many university anthropologists, believed that the Neanderthal blood line at least has continued to the present day. Now that there is DNA evidence supporting the idea that Neanderthals live on within us, we’d be tempted to say that interest in
the Neanderthals has increased, even though their place in our cultural lexicon was already well established. Plus, the Saul Leviticuses of this world will only be happy if a lost tribe of Neanderthals is found hiding on a mountain, probably in Asia. For most of us, Neanderthals are little more than a symbol, as we invoke their name to criticize brutish behaviour and appearance. The notion of a super-strong species of humans with strangely shaped faces who looked and acted much as we did until around 40,000 years ago is certainly unforgettable. But how close are pop culture Neanderthals to the genuine article?
Although we know a great deal of the Neanderthals’ specific history, for most people they occupy roughly the same cultural space as cavemen. Their name is a synonym for primitiveness, brutality, backward thinking and generally being out of step with the times. In most cultural references, the two terms are interchangeable.
The US insurance firm GEICO created a brilliant parody of this simplistic view of our predecessors in a series of TV commercials starting in 2004. In the ads, a group of self-styled cavemen, or ‘cro-maggers’ (short for Cro-Magnon), who survived to the present, struggle with the negative media stereotypes about them, especially in GEICO’s own non-politically correct campaign to sign up new customers: ‘so easy, a caveman could do it’. Living among us as a sort of ethnic minority, the joke is that they are offended by the way we use ‘caveman’ as a term of derision. Though not called Neanderthals, their appearance – wide noses, heavy brow ridges, prominent teeth – is unmistakable. True Cro-Magnon men would look just like modern human men, and the humour would have been lost. This series of commercials evolved into a sit-com called ‘Cavemen’, whose very brief tenure on the network ABC was both a reflection of the thinness of the gag and a fitting outcome for Palaeolithic hold-overs who went extinct so long ago.
The Neanderthals Rediscovered: How Modern Science is Rewriting Their Story Page 16
