In contrast, the psychologist Michael Corballis returned to Darwin’s views on the importance of gestures as precursors of language, arguing that the brain areas that are important for language production in humans are actually concerned with manual actions in other primates. Similarly, the psychologist Michael Tomasello sees language as having evolved as a practical social tool for communication regarding requests, information, and cooperation. In his view, speech is the ultimate, and perhaps ultimately evolved, component of what we call human language, but it could have been preceded by gestures, just as it often is in human babies. Indeed, there is considerable evidence that we do communicate with each other—sometimes unconsciously—through our body language and posture, still an important vestige of our prelinguistic primate heritage. Other researchers have argued for a link between brain coding for toolmaking and for language, since both are sequential processes involving intention and finely controlled muscle actions; thus children learn to manipulate and assemble words as they are also manipulating and assembling objects. And it is certainly possible that parts of the brain that were already there and fulfilling different functions were co-opted to cope with the growing demands generated by language for storage, processing, and muscle control.
From my perspective, modern human language probably evolved out of growing social complexity over the last 250,000 years to bolster mind reading and communication, and I agree with the archaeologist Steven Mithen that by enhancing cognitive fluidity, language took modern humans into new and shared worlds that were unknown to our ancestors. The Neanderthals must have been highly knowledgeable about the world in which they lived, too (for example, about the materials from which they made tools and the animals they hunted). But in my view their domain was largely of the here and now, and they did not regularly inhabit the virtual worlds of the past, the future, and the spirits. After our evolutionary separation about 400,000 years ago, we and the Neanderthals traveled down parallel paths of developing social complexity and, with it, developing language complexity. For whatever reasons, we traveled farther, and the Neanderthals came to the end of their long road about 30,000 years ago.
Attempts have been made by scientists like Philip Lieberman and Jeff Laitman to reconstruct the speech capabilities of Neanderthals and other early hominins, based on the shape of the base of their skulls and the position of critical anatomical landmarks. In their view, modern humans possess a uniquely shaped tongue, throat, and vocal tract, facilitating the range and complexities of sounds required for fully human speech. Darwinian selection must have operated on variations in skull form, leading to its restructuring, and the modification of the throat from its previous dominant functions of breathing and swallowing toward the complexities of modern human speech capabilities, as long as the newly acquired vocal skills conferred advantage. The price we paid for this reshaping of priorities in the throat is a greatly increased risk of choking on our food compared with chimps and early hominins. In the case of the Neanderthals, their vocal tracts and capabilities were apparently closer to those of a two-year-old child than a modern adult; however, there is no doubt that if the Neanderthal brain was coding for complex language, even that kind of vocal tract would have done the job, albeit with a more restricted repertoire of sounds.
Returning to the checklist of modern human attributes that I discussed in the previous chapter, in my view modern humans had developed most of them by 60,000 years ago, even if they were not always present as a package all of the time from the evidence we have found so far: that is, complex tools, the styles of which may change rapidly through time and space; long-distance transport of valued materials such as stone, shells, beads, amber; evidence for ceremonies or rituals from art, structures, or complex treatment of the dead (the latter inferred from the Skhul and Qafzeh symbolic burials). But for some of the attributes, the evidence so far is either equivocal or only partly there, including formal artifacts shaped from bone, ivory, antler, shell, and similar materials; greater complexity of food gathering and processing procedures, such as the use of nets, traps, fishing gear, and complex cooking; art, including abstract and figurative symbols; and structures such as tents or huts for living or working that are organized for different activities such as toolmaking, food preparation, and sleeping and for hearths. Regarding higher population densities approaching those of modern hunter-gatherers, I will discuss this aspect later, in chapter 7, from the perspective of genetic data. And regarding increased cultural “buffering” to adapt to more extreme environments such as deserts or cold steppes, it may be that this aspect evolved more gradually as modern humans grew in numbers and dispersed to the ends of the Earth.
In chapter 4 I discussed how fossil foot bones from Europe and China showed that early moderns in both regions had seemingly discovered the benefits of footwear, and patterns of objects, such as sewn beads, pins, and toggles, in Cro-Magnon burials imply the existence of fitted clothing, as does the presence of eyed bone needles. Clothing would have been of great value to humans in colder climates, and although direct evidence for it has perished, it seems likely that the Neanderthals had the skin-working technology required to make at least basic clothes to keep the cold and wet off their bodies.
Replica of a mammoth carved from reindeer antler, from the Montastruc rock shelter, France. The original formed part of a spear thrower (atlatl) and is about 14,000 years old.
Many modern peoples in tropical and subtropical regions often wear little or no clothing, beyond what may be required for reasons of modesty or tradition, and humans do have the ability to adapt physically to colder climates. When Darwin and the Beagle visited the bitterly cold regions of Tierra de Fuego at the subpolar tip of South America, he was astonished to see that the native peoples wore little or no clothing and slept naked in the open. Native Australians also have physical adaptations that help them sleep at night in the outback, but interestingly Europeans seem physiologically poorly adapted to the cold—something they do not seem to have acquired from the Neanderthals, despite the likelihood of interbreeding. However, cold conditions were also present in Africa, in the highlands and in cloudless areas at night, and basic clothing and warm bedding would have been advantageous at times.
With the lowered temperatures of the last Ice Age, moderns in parts of Africa 60,000 years ago would certainly have benefited from clothing and warm bedding. Although we have no direct evidence of these from that time period, we do have some genetic clues. Humans are infected by head and body lice, and while they both feed by blood-sucking through our skin, the latter live and lay their eggs on clothing and bedding, a fact that both Mark Stoneking and Melissa Toups and their colleagues utilized for evolutionary studies. Both teams reasoned that the origin of the distinct form of body lice probably corresponded to the opportunity provided by the regular use of clothing and bedding. Using mtDNA molecular clocks of lice evolution in humans and apes, they estimated the origin of body lice to between 80,000 and 170,000 years ago. This in turn suggested that bedding and clothing could already have been in use by modern humans in Africa, and they then took this valuable innovation with them when they left their ancestral homeland—together with the lice. However, there is another possibility to consider. The archaeologist Timothy Taylor quite rightly highlighted the invention of the baby sling as a crucial development for the way that it liberated women from the restrictions of baby carrying and the confines of static nursing, and he considers this must have happened relatively early in human evolution. But if the innovation actually happened with modern humans, in Africa, this could have provided a new home and jumping-off point for those pesky lice.
A more welcome fellow traveler on the modern human diaspora from Africa may have been the dog, the first known domestic animal. There is evidence that Aurignacian people living in Goyet Cave, Belgium, already had large dogs accompanying them about 35,000 years ago. The dogs were anatomically distinct from wolves in their shorter and broader snout and dental proportions, and isotope data sugges
t that they, like the humans, were feeding off horses and wild cattle. Moreover, ancient dog DNA was obtained, which showed that the Belgian dogs were already genetically diverse and that their mitochondrial sequences could not be matched among the large databases of contemporary wolf and dog DNA. These findings are important because they suggest that dog domestication had already been under way well before 35,000 years ago.
So where were the first dogs domesticated? That is a very difficult question to answer from modern dog and wolf DNA, with no clear single link between the two species or subspecies. Indeed, it is quite likely that domestication happened more than once, in different regions and from distinct wolf stocks. Given the Pleistocene range of the wolf, the first event might have occurred in western Asia, soon after modern humans reached there about 55,000 years ago or, as some DNA data suggest, farther east in Asia. It may have happened through the adoption of cubs, or perhaps through a gradual relationship of tolerance as wolves hung around human campsites. With selective dog breeding and adaptation to each other, a special relationship probably developed quickly. (In Russia, silver foxes were bred to behave like dogs over a period of only fifty years.) Ancient dogs obviously bred successfully, and for humans the advantages of having them to provide extra (and more acute) eyes, noses, and ears, as well as speed and fangs, were clear. And coevolution occurred—dog brains are on average some 25 percent smaller than wolf brains, and yet they have many skills that wolves lack. For example, even as puppies, they can follow human pointing to find hidden objects, and their powers of attention and imitation match or exceed those of apes, suggesting quite sophisticated cognition and mind reading in the social domain. And if Aurignacian Cro-Magnons were regularly accompanied by dogs, could this have been another advantage they had over the last of the Neanderthals?
There are some other important issues in the Out of Africa dispersal related to behavior that also need to be addressed. If and when modern humans encountered the Neanderthals, how much would behavioral differences between them have affected the way they saw each other? Would they have perceived each other simply as other people, enemies, or even the next meal? We don’t know the answer, and it may have varied from one time and place to another, especially given the vagaries of human behavior. These populations had been diverging from each other for much longer than any modern human groups who encountered each other in the Americas and Australia during the colonial “Age of Discovery.” In my view there were probably deep differences in appearance, expression, body language, general behavior, and perhaps even things like smell, which would have impinged on how the Neanderthals and early moderns perceived each other. As an example that seems to apply even to the relatively closely related populations of Europe and the Far East today, there is some evidence that these groups read facial expressions somewhat differently—Europeans using the whole face, and East Asians focusing more on the eyes as cues for ascertaining mood. As a result, Asians (in an admittedly small sample) were more likely to read European facial signals for fear as indicating surprise, while they more often took disgust to indicate anger. If such differences have arisen within modern humans in the last 50,000 years, the potential for misreading between Neanderthals and moderns might have been even greater. Such factors, as well as possible differences in language, symbolic communication, and social structure, would have been every bit as important as the physical ones in determining whether interbreeding happened, and what were the fates of any offspring that may have resulted from it.
What the symbolic repertoire of Neanderthals actually was remains a subject of hot debate. While early moderns in Africa seemed to have preferred the bloodred signaling of hematite, there is evidence (discussed shortly) that groups of Neanderthals in Europe utilized dark pigments such as manganese dioxide and even pyrite. Some of this may have been for functional reasons, as has also been suggested for hematite, such as treating hides and mixing with resins to form an adhesive. But with emerging genetic data that some Neanderthals were pale-skinned (see chapter 7), it might well be that red pigments showed up best on dark-skinned Africans, while black pigments would have been favored by lighter-hued Neanderthals. Of course, even marking skin with pigment could have had a functional purpose in the Neanderthals, camouflaging them for ambush hunting, but there are other controversial indications that they were signaling symbolically—but to whom?
The Grotte du Renne (Reindeer Cave) at Arcy in France is a site that, like Saint-Césaire, has demonstrated the association of Neanderthals with the “advanced” Châtelperronian industry. There are not only the characteristic stone tools of this industry but also parts of a Neanderthal child’s skull and isolated Neanderthal teeth. But more surprisingly there are animal teeth pierced to make pendants, and fragments of worked bone and mammoth ivory. These latter items are, of course, also characteristic of the Aurignacian industry, which seems to have been the product of early Cro-Magnons. So what was going on here? There are several possibilities, each of which has support from one group of archaeologists or another. One is that the symbolic objects were not made or used by Neanderthals but were in fact the products of modern humans—either ones who briefly visited the site and left items like the pendants there or ones who lived there later, following which the cave deposits became mixed or were not excavated well enough to distinguish the separate occupations. In support of this view is recent radiocarbon dating of the site that suggests that the Châtelperronian deposits in particular suffered disturbance and mixing. But against it, there is the fact that other Châtelperronian sites in France and Spain show similarly “advanced” stone and bone tools like those at Arcy, and at least one other contains pendants.
A second point of view is that the symbolic items were made by moderns but had been traded into Neanderthal groups, or that the Neanderthals had picked them up in a nearby Cro-Magnon site. A third suggestion is that the Neanderthals were acculturated by contemporaneous moderns—that is, they were influenced by them and were, for example, copying their jewelry styles. And a fourth idea is that the Neanderthals were in fact continuing their own independent tradition of developing complexity, and undergoing a parallel process of becoming “modern”—but in a Neanderthal way!
Neanderthals used pigments too—these are of manganese dioxide from Pech-de-l’Azé in France.
In support of that last viewpoint, there is arguably even stronger evidence of complex Neanderthal social behavior from two Middle Paleolithic cave sites in southeastern Spain (Cueva Antón and Cueva de los Aviones). There, museum studies and excavations led by the archaeologist João Zilhão found seashells that had apparently been used symbolically. Cockle and scallop shells with natural holes in the right places to be strung as pendants had been collected and transported inland. Some of the shells had light or dark pigments stored in or painted on them, and a thorny oyster shell contained ground pigment that had apparently been mixed with pyrite as a glittering cosmetic. While the painted scallop from Cueva Antón was probably less than 40,000 years old, and therefore might reflect Cro-Magnon influence, the Cueva de los Aviones material dated to about 50,000 years ago, seemingly too old for that explanation to apply. But in either case these sites represent strong evidence that at least some Neanderthals were expressing themselves symbolically, seemingly as much as many Middle Stone Age Africans, and I will return to this question in the next chapter.
In 1993 Clive Gamble and I argued that the Neanderthals had absorbed aspects of Cro-Magnon culture, but while they could “emulate … they could not fully understand.” Now I would say instead that if the Neanderthals were making or just using objects like pendants, they were participating in symbolism just as the moderns were, whether they were signaling within their own groups or to others, who might at times have even included early Cro-Magnons. And if that is so, the idea that these aspects of modern human behavior resulted solely from genetic changes in African Middle Stone Age peoples must be wrong, unless the Neanderthals had undergone similar mutational changes in their own evo
lution, or they had acquired the modernizing genes by hybridization—a subject I will discuss in more detail in the next chapter.
7
Genes and DNA
Like many people I am curious about my origins and so was pleased when the geneticists Bryan Sykes and Alan Cooper wanted to sample and determine my DNA—or at least the tiny bit of it contained in the mitochondria of my cells (mitochondrial DNA). But they had a practical purpose in mind as they were pioneers in the extraction of DNA from human fossils, and they wanted to be able to exclude any of my DNA that might be contaminating the fossils I had handled, or even briefly touched. They were fortunate as I had a couple of unusual mutations in my mtDNA, which makes it very recognizable, but it was still somewhat shocking to find that my DNA had left a contaminating trail across the museums of Europe! As Alan Cooper is jokily fond of accusing paleoanthropologists, in terms of the contamination of fossils he has tried to study, “You are all very dirty people!”
In this chapter we will look at the huge amount of genetic data about the evolution of our species and our diversity now being generated, and address the origin and significance of regional (“racial”) differences. The genetic data can be used to look at the demography of ancient humans in Africa, the size of our ancestral pool of people, and the numbers that may have left Africa to found the populations of the rest of the world. They can also be used to estimate dates for events in our evolutionary history, such as our split from the Neanderthals and when our modern human ancestors first moved out of Africa. In addition, in the last decade, scientific breakthroughs gave us tiny but invaluable glimpses of the genetic makeup of the Neanderthals and are now providing a nearly complete Neanderthal genome to compare with ours and with that of chimpanzees. This three-way comparison will illuminate what makes each species really distinct and will lead the way to reconstructing, at least to some extent, what the Neanderthals looked like in the flesh, and perhaps even the humanness of their brains and ways of thinking. Along with discussion of the genetic data, I will give my views about the evidence of mating between Neanderthals and modern humans.
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