Others point to the sizes of endocasts to infer that Homo erectus were already linking their minds differently from the way their ancestors did. As noted earlier, whereas primates groom each other to form group cohesion, human group members typically bond by talking to each other and sharing experiences. Robin Dunbar highlights the role of gossip as a means to bond and has come up with a way to estimate when a switch from grooming to gossip might have occurred. He has shown that the larger the typical social group of a primate species, the larger their neocortex ratio. By plugging values for extinct species into the formula that describes this relationship, he estimated the different group size various hominins were likely to have lived in.18 If correct, then the last three million years saw a steady increase in group size from about 60 in Australopithecines to over a hundred in Homo erectus and up to 150 in modern humans.19 Once you have an estimate of typical group size, you can predict (at the risk of introducing another estimation error) the time that each species is likely to spend on grooming. While Australopithecines may still have been able to maintain group cohesion through grooming some 20 percent of their waking time, Homo erectus would have had to spend a third of their days grooming each other. Such a requirement would seriously cut into the time available for other essential behaviors. Perhaps our capacity to connect our minds emerged around the time Homo erectus could no longer effectively connect through physical touch alone.
We lack hard evidence for an increased urge and capacity to link minds.20 Yet one recent find may indicate a marked shift in the social mind of early Homo. A 1.77-million-year-old skull from Dmanisi in Georgia is of an elderly man without teeth and with advanced subsequent bone loss—implying he survived for a significant time without being able to chew. The other group members may have done the chewing for him.
There is much we do not know, but the minds of Homo erectus were clever enough to allow them to spread across the old world and survive in diverse habitats for hundreds of thousands of years.
SOME DESCENDANTS OF HOMO ERECTUS became robust and acquired modern human characteristics. These fossils are sometimes lumped together under the umbrella label “archaic” Homo sapiens or premodern humans—another set of not-missing links. A variety of potentially separate species coexisted from 800,000 years ago onwards in Africa, Asia, and Europe. The oldest member of this group is a hominin from Spain called Homo antecessor. It had a relatively flat face, a high domed forehead, and a cranial capacity of just over 1,000 cubic centimeters. The first archaic fossil to be described was a robust and chinless jawbone from near Heidelberg, Germany, leading to the name Homo heidelbergensis. Many archaic fossils have since been found in central Europe, with a few in Africa and Asia. Homo heidelbergensis lived between 600,000 and 150,000 years ago. They stood up to 1.8 meters tall and were robust, with immensely thick brow ridges and a large brain with an average cranial capacity of 1,200 cubic centimeters.
Homo heidelbergensis probably cooperated in various ways. A spine of a five-hundred-thousand-year-old specimen from Spain shows a hunched back. Such a condition would have meant significant incapacitation, suggesting that this forty-five-year-old received help and support from others. They seemed to have cooperated to bring down big game; numerous remains were found in association with stone tools. Unlike with Homo habilis butchering sites, the bones now show initial stone-tool cut marks and only later carnivore teeth marks. Remarkably, four-hundred-thousand-year-old spears were discovered near Bielefeld, Germany, together with ten butchered horses and flake stone tools, strongly suggesting cooperative big game hunting. It is possible that these spears were used primarily to thrust, but they may well have been thrown, and replicas suggest an effective range of some fifteen meters.
Making these spears would have required stone tools. Making a tool to make other tools suggests some capacity for nested scenario building. Archaic Homo may have made other significant strides toward modern minds. Ash deposits and charred bones suggest the capacity to control fire. In 2010 evidence for stone blades from Kenya were dated at over five hundred thousand years old, suggesting some planning to repeatedly produce blades from a single core.
From around three hundred thousand years ago onwards, Acheulean bifaces were increasingly replaced by smaller cores and flakes (known as the Levallois technology). Producing these tools requires complex steps and the coordination of subgoals. A nucleus is shaped and a striking platform prepared to reach the overarching goal of producing one specific smaller flake (or several). Carrying a core, rather than a bifacial hand ax, made it possible to produce specialized tools on the spot as required. New tools were invented. The hafting of stone tips, for instance, appears to have begun around that time (although some recent evidence suggests it may have emerged as early as five hundred thousand years ago). That is, tools were produced not only out of an existing object but by adding parts. Composite tools strongly suggest a capacity to imagine hierarchical, nested, mental scenarios. To make a spear with a stone point, for instance, one has to make the shaft, the point, and the binding in separate steps. Archaeologists, such as Stanley Ambrose and Ceri Shipton, suggest that the emergence of composite tools, such as stone-tipped spears and knives, indicates a dramatic change in mental capacity. Assembling units in different configurations produces new tools, much like assembling words in different configurations produces new sentences.
FIGURE 11.8.
Homo heidelbergensis (Atapuerca-5), three-hundred-thousand-year-old skull from Spain.
ARCHAIC SAPIENS LIKELY GAVE RISE to both our own species and our most famous prehistoric cousins, the Neanderthals. The first recognized Neanderthal fossils were unearthed in 1856 in the Neander Valley in Germany. Today over two hundred fossils have been described. Neanderthals lived from about 160,000 years ago to as recently as 27,000 years ago, during a period of extreme climate changes that would have posed major survival challenges. They were a stocky people adapted to the cold, with large noses and protruding brows. The size and shape of their inner ear canals were distinctly different from that of modern humans. Some of them had pale skin and red hair.
FIGURE 11.9.
Homo neanderthalensis (La Ferassie 1), fifty-thousand-year-old skull from France.
Neanderthals lived in small groups, at times occupying caves, and ranged across ice-age Europe to the Middle East. Recent evidence suggests they may have moved much farther east than previously thought, up to western Siberia. They were game hunters and largely depended on meat for sustenance. Their front teeth show unusual wear, potentially because they used them to hold items. Evidence from Gibraltar indicates that they exploited a variety of food sources, including fish and dolphins (which they may have scavenged from the beach). There is some indication, such as bones opened to extract marrow, that some Neanderthals practiced cannibalism.
In 2010 DNA from three 38,000-year-old female Neanderthals from Croatia was extracted to construct a draft sequence of their genome. Evidence thus far suggests the last common ancestor of humans and Neanderthals lived between 440,000 and 270,000 years ago. Mitochondrial DNA extracted from thirteen Neanderthals subsequently indicated there was great genetic variation before 50,000 years ago, but that younger specimens from Western Europe showed much less variation. This result may be due to a mass extinction around that time, during which cold periods engulfed Europe, and the surviving few recolonized as the weather improved. As noted in Chapter 1, the results of ancient DNA comparisons show that modern non-Africans have inherited some Neanderthal genes. So in a sense, Neanderthals are not entirely extinct after all.
FIGURE 11.10.
Mount Carmel Caves on the Mediterranean coast close to Haifa. The caves were used for over half a million years, with traces from the Acheulean to modern humans. For thousands of years Neanderthals and modern humans seem to have lived here side by side, or at least repeatedly visited the region (with warmer weather modern humans moved north, and with colder weather Neanderthals spread south). This is where they probably interbred.
The current evidence suggests, however, that the degree of intermixing was small, so the general idea that modern humans replaced earlier populations is still mostly true. Neanderthals probably interbred with modern humans in the Middle East around eighty thousand years ago, when they cohabited the region for thousands of years (see Figure 11.10). Modern humans eventually migrated into a Neanderthal-inhabited Europe some forty thousand years ago. As they moved farther west, Neanderthals began to disappear, and by thirty thousand years ago only a few remained on the western coasts of Spain and Portugal.
The traditionally brutish image of Neanderthals has been revised in recent years. Their brains were as large as—and some even larger than—ours, with a mean cranial capacity of 1,426 cubic centimeters. Neanderthals survived into relatively old age in spite of severe disabilities caused by wounds, arthritis, and broken bones, suggesting that they cared for the sick and had some capacity for empathy, cooperation, and social norms. Furthermore, evidence of Neanderthal burials suggests that they may have had some sense of the future beyond an individual’s lifetime and possibly held spiritual beliefs. They evidently used fire and wore clothes, and they hunted not just old, injured, or weak animals but prey in their prime. Their minds were undoubtedly much more like ours than that of an ape.
Neanderthals show clear evidence of having made composite tools and therefore of possessing some capacities for nested thought. Did they have our urge to connect their minds and our means to do it? Dental growth patterns suggest that Neanderthals may have grown up more quickly than modern humans (and even faster than earlier archaic Homo), which would indicate less time to educate the young. However, recent findings raise the possibility that Neanderthals engaged in some human social signaling: they may occasionally have worn shells as jewelry and used ochre as paint. It has even been posited that some of them produced cave paintings. Archaeologists are hotly debating whether modern humans left these signs of symbolic thought, whether Neanderthals copied these behaviors from modern humans, or if the behaviors independently emerged in our cousins. It is certainly possible that they had symbolic capacities to exchange their minds.
Yet did they have the physical capacity to speak? The cognitive scientist Philip Lieberman has long argued, based on reconstructions of their vocal tracts, that Neanderthals would not have been able to make the phonetic elements necessary for speech. The discovery of a 60,000-year-old Neanderthal hyoid bone, a free-floating bone located in front of the voice box (larynx), challenged this conclusion because it was essentially modern in size and shape, suggesting that the Neanderthal voice box was much like that of modern humans. A recent find of a hyoid bone from an earlier archaic Homo sapiens suggests this modern form may already have emerged some 500,000 years ago. By contrast, a 3.3-million-year-old hyoid bone of an Australopithecus afarensis is more similar to that of modern great apes. Further clues come from recent DNA analyses. Neanderthals were found to have the modern version of a gene strongly implicated in human speech.21 This gene appears to have emerged before the split between the lines leading to Neanderthals and modern humans, and it therefore points to an ancient origin. There are many pieces to the speech puzzle, however, and it remains uncertain when hominins started to speak.
To make matters worse, language may not have started with speech at all—it is possible that gesturing preceded talking. Although attempts to teach other primates to speak have been failures, some great apes have successfully learned to use gestures to communicate. One stumbling block is that primate articulations, unlike their hand movements, are primarily emotive and not under voluntary control. Michael Corballis has championed the idea that gestural communication became more sophisticated in early hominins, perhaps initially based around declarative pointing and iconic mime. Language may have gradually evolved in the gestural domain. Only in modern humans, Corballis argues, was gestural language supplanted with speech—which you could argue are gestures produced by the tongue. Sign languages are languages that simply use a different modality (and we still tend to gesticulate when we talk). If this account is correct, then even if Neanderthals and earlier hominins could not speak, they might have had sign language.
ANATOMICALLY MODERN HUMANS GO BACK some 200,000 years. Analyses of teeth suggest that by 160,000 years ago our ancestors had a modern human life history. Yet compelling evidence for a fully modern human mind emerges significantly later. The oldest clear evidence for a human burial, for example, is a 119,000-year-old site at Skuhl Cave, Israel (see Figure 11.10). The earliest evidence for ornamentation and potential ethnic signaling are 82,000-year-old shell beads from Morocco with signs of wear and traces of ochre. Slightly younger beads (75,000 years old) were found at Blombos Cave in South Africa. In this same cave were found the earliest known examples of abstract-looking designs: geometric patterns engraved in ochre and in bone. Evidence for long-range projectile weapons in the form of potential arrowheads also appears around this time, as does evidence for compound adhesives. Recent finds from South Africa show that by 40,000 years ago artifacts such as bone tools and poisoned arrowheads are nearly identical to those still in use today by San hunter-gatherers. This is evidence of continuity in material culture and lifestyle.
The oldest known representational paintings, dated at thirty-two thousand years ago, are located in the Chauvet Cave in France, portrayed in Werner Herzog’s film Cave of Forgotten Dreams. From this period onwards symbolic capacities are expressed in a range of other domains including sculptures, engravings, and even musical instruments. Controversial new dates from the prehistoric cave of Geissenklösterle in Germany suggest that figurines and flutes were produced even earlier, around forty thousand years ago. Among the early works of art is the famous Hohlenstein-Stadel figurine, which comprises lion and human parts and so demonstrates a creative capacity to combine basic elements into novel constellations.
Yet most early cave art lacks any obvious narrative. The oldest apparent scenario with a story line I could find comes from one of the most wonderful caves ever discovered. In 1940, eighteen-year-old Marcel Ravidat looked for his dog, Robot, on a hill near the river Vezère when he stumbled on a hole in the ground. He and three friends returned four days later and forced their way into the tunnel armed with knife and torch. They discovered Lascaux Cave, its walls covered in colorful paintings of some nine hundred animals, such as bulls, horses, and stags. About seventeen thousand years earlier human painters went into the cave with reindeer-fat torches, made scaffolds, and then painted the walls with extraordinary realism. In the lowest part of the cave, known as the Pit, is the only painting of a human and what appears to be a depiction of an event (see Figure 11.11).
One might interpret the scene as a hunt gone wrong. The human figure is lying on his back with a bison charging toward him. The bison appears to have been hit by a spear and looks as if its entrails are falling out. Next to the fallen man is a stick with a bird on it—possibly a spear thrower. On the other side of the man are two parallel series of three dots and a woolly rhinoceros. Perhaps the rhino disemboweled the bison and caught the man. Perhaps not. Diverse interpretations have been advanced, including some esoteric proposals involving stars, spirits, dreams, or trance. Most commentators agree that the painting tells a story, although it is far from obvious what that story is.
FIGURE 11.11.
Reproduction of the Pit scene at Lascaux. The first illustrated story?
LESS THAN A KILOMETER FROM Lascaux, Roger Constant dug on his farm in search of an entrance to the famous cave. He was unsuccessful but instead found a seventy-thousand-year-old burial site: a Neanderthal in fetal position surrounded by bear bones.
Neanderthals were no longer around when Lascaux’s famous paintings were made, but until their eventual demise, they seem to have been evolving culturally. Michelle Langley and colleagues have shown that their behavioral complexity increased over time, just as it did in anatomically modern humans. In some instances the technologies of modern humans were advanced, but in others t
hey were not and were even inferior. There are signs that earlier inventions were lost for thousands of years before they reemerged. The archaeological record complicates the simplistic view that modern humans gradually ratcheted up sophisticated technology and displaced populations of brutish Neanderthals. It increasingly looks like local factors, such as climate, population densities, and conflicts, played a major role in the diffusion, accumulation, or loss of particular cultural inventions.
One potentially telling difference between post-Neanderthal humans and earlier hominins is that the ratio of younger to older adults shifts in the fossil record. An analysis of fossil teeth from over 700 individuals found numbers of old to young hominins gradually increased from late Australopithecines (37 old, 316 young) to early Homo (42 old, 166 young) to Neanderthals (37 old, 96 young). Post-Neanderthal Stone Age Europeans, by contrast, are disproportionally represented by older individuals (50 old, 24 young).22 This points to a better survival rate and hence opportunity to accumulate cultural information. An individual was considered old when it was twice the age of expected reproductive maturity. In other words, the individual could conceivably have been a grandparent. Only when older age becomes reasonably common might we expect the grandmother effect to have had significant traction.
The Gap Page 31
