The evidence for cooking among Homo ergaster is very thin, but the evidence for migration is unequivocal. Gradually small groups migrated out of East Africa onto the open plains of Central Africa, and from there into northern Africa. From 1 million to 2 million years ago the earth's climate was in a warming phase, and Homo ergaster ranged still farther, moving into western Asia by as early as 1.8 million years ago. Here some developed into a species that many paleontologists call Homo erectus (“upright human”), although others see ergaster and erectus as two names for the same species. (Homo ergaster and Homo erectus are currently broad and variable species categories, encompassing many subgroups.) They continued to migrate: bones and other materials from China and the island of Java in Indonesia indicate that Homo erectus had reached there by about 1.5 million years ago, thus migrating over large landmasses as well as along the coasts. (Sea levels were lower than they are today, and Java could be reached by walking.) Homo erectus also walked west, reaching what is now Spain by at least 800,000 years ago, and then further north in Europe. In each of these places, Homo erectus adapted gathering and hunting techniques to the local environment, learning about new sources of plant food and how to best catch local animals.
Map 1.1 Homo ergaster/Homo erectus migrations
A Homo erectus site in the modern country of Georgia dating from about 1.8 million years ago provides the first evidence of compassion or social concern in the fossil record. One of the skulls recovered was that of an aged man who had lost all but one of his teeth, but lived for a number of years after this. This would only have been possible had those who lived with him helped him.
There is no clear evidence in the fossil record of symbolic thought among Homo ergaster/erectus—no decorations, no artwork, no sign of body adornment. Those who take a more expansive view of culture point out, however, that hand axes found over a huge area and a long period of time were symmetrical and uniform, which may simply have been a matter of practicality and usefulness, but may also have represented a conceptualization of what was “good.” They were often made in great quantities at a single site, which again may have simply been a practical matter of locations with especially good stone, but suggests some degree of specialization of labor or social roles. At a few of these sites thousands of hand axes remain and a few are far too large to have been tools; might these have been ritual or ceremonial objects, or the maker showing off unusual talent?
Suggestions about social differentiation or culture among Homo erectus are very controversial, but those about slightly later species of hominins are a bit less so. One of these was Homo heidelbergensis, found throughout much of Afroeurasia between 600,000 and 250,000 years ago, with a brain close to that of modern humans in size. Some built simple shelters, and, as noted above, after 400,000 BCE many sites show evidence of controlled fire. One of these is Terra Amata in what is now southern France, where there were also pieces of red and yellow clay carried in from far away. These were probably used as pigment, again suggesting some notion about what was attractive or important. A bog in Germany has yielded evidence of cooking hearths and the oldest preserved wooden tools (long sharpened wooden spears and what look like wooden handles for stone blades) from about 400,000 years ago, the earliest indication of composite tools. A pit at the bottom of a deep shaft within one of the caves in the Atapuerca region of Spain contains remains of at least twenty-eight individuals, dating from at least 350,000 and perhaps as early as 600,000 years ago. These individuals must have been put there intentionally after they died, which makes Sima de los Huesos (the pit of bones) the earliest known site of burial, a practice with huge cultural implications. At a site in Kenya, archaeologists have found disks of ostrich eggshell from about 280,000 years ago with holes bored in them, so that they could have been worn on a strand, and in Israel archeologists discovered what some argue is the first evidence of artistic production—a small stone shaped like a female torso, from about 230,000 years ago.
The group at Sima de los Huesos appears to have been the ancestors of the most famous non-Homo sapiens species of hominins, the Neanderthals (named after the Neander Valley in Germany, where their remains were first discovered). Neanderthals lived throughout Europe and western Asia beginning about 170,000 years ago, thus initially alongside Homo heidelbergensis. They had brains as large as those of modern humans, although dental evidence suggests that they matured earlier, so had a period of dependence on others—and thus perhaps of learning—shorter than ours. They used complex tools, including spears and scrapers for animal skins, that enabled them to survive in the diverse environments and climates in which their bones have been found, from the shores of the Mediterranean to Siberia. Judging by wear and tear on skeletal remains, both males and females engaged in the same type of hard physical labor, and died at similar ages. They built freestanding houses, and controlled fire in hearths, where they cooked animals, including large mammals (as evidenced by stable isotope analysis) and many kinds of plants (as evidenced by their tooth plaque). Their tools appear to have changed somewhat over time, and show signs of being made in several stages, not just on the spot as need required. Thus Neanderthals exhibited technological inventiveness and long-range planning, characteristics that scholars such as Francesco d'Errico have described as part of “behaviorial modernity,” even if anatomically they were not Homo sapiens.
Evidence from one 50,000-year-old Neanderthal site in Spain has yielded intriguing suggestions about Neanderthal society. Here twelve individuals of various ages appear to have been killed and eaten by another group, during a period—judging by the tooth enamel of the victims—of food scarcity. DNA evidence shows that these twelve individuals were related, and that the adult males were more closely related than the females. Thus the men had most likely stayed with their birth family, while the women had come from other families, a pattern that would be replicated later among Homo sapiens of many eras and places. Two of the children were offspring of the same woman, and were about three years apart in age; this birth interval, perhaps the result of long breast-feeding, is also something that would be replicated among many later foragers. This site provides an unusual opportunity to glimpse Neanderthal social relationships, both hostile and caring.
Materials unearthed in many locations also indicate that Neanderthals sometimes buried their dead carefully, and occasionally decorated objects and themselves with red ochre, a form of colored clay. Burial and body decoration seem so characteristic of modern humans that Neanderthals were originally categorized as a branch of Homo sapiens, but DNA evidence from Neanderthal bones now indicates that they were a separate species that developed from a different line of Homo erectus than we did.
1.2 Sculpted model of a female Neanderthal, based on anatomy from fossils and DNA evidence, which reveals some Neanderthals carried genes for red hair and blue eyes. The artists chose the facial expression they did to reflect the harsh conditions of life, and added decorative body painting because lumps of pigment have often been found at Neanderthal sites.
In the last few years, DNA evidence has also been used to provide further details about non-Homo sapiens hominins. It suggests, for example, that Neanderthals and Homo sapiens occasionally had sex with one another, for between 1 and 4 percent of the DNA in modern humans living outside of Africa likely came from Neanderthals. Bones and teeth dating from about 40,000 years ago found in the Denisova cave in Siberia in 2010 have yielded DNA that is distinct from both Neanderthals and Homo sapiens, although the Denisovans also shared some genetic material with both groups, thus suggesting that they interbred with them. Whether they also shared social organization or ideas is not revealed by anything remaining at the site.
The last evidence of Neanderthals as a separate species comes from about 30,000 years ago, and until very recently they were thought to be the last living hominins that were not Homo sapiens. In 2003, however, archaeologists on the Indonesian island of Flores discovered bones and tools of three-foot-tall hominids that dated from only a
bout 18,000 years ago, which they nicknamed “hobbits.” (Lawyers for the Tolkien estate are trying to block the use of that nickname to describe these small individuals, arguing that it is copyrighted.) They appear to be a distinct species, probably descended from Homo erectus just as were Neanderthals, and to have lived on the island for more than 800,000 years. Like the DNA evidence from Siberia, the physical evidence from Flores has just begun to be interpreted and has occasioned much controversy, but few dispute that these and other recent finds demonstrate that the human evolutionary path is more complex and multi-branched than we used to recognize, more of a bush than a pine tree.
Thinking humans
Neanderthals, Denisovans, Homo floresienses and other species and sub-species of hominins not discussed above or yet to be discovered, classified, and named lived in many parts of Afroeurasia. A few scientists think that Homo sapiens (“thinking humans”) evolved from several of these branches, but the majority think that, like hominid evolution from earlier primates, this occurred only in Africa. The evidence is partly archaeological, but also genetic. One type of DNA, called mitochondrial DNA, is inherited through the maternal line and can be traced far back in time. Mitochondrial DNA indicates that modern humans are so similar genetically that they cannot have been evolving for the last million or 2 million years, but only for about 250,000 years or perhaps even as little as 200,000 years. Because there is greater human genetic variety today in Africa than in other parts of the world, the evidence also suggests that Homo sapiens have lived there the longest, so that Africa is where they first emerged and all modern humans are descended from a relatively small group in East Africa. (Picking up on the biblical story of the first humans, some scientists have given the name Mitochondrial Eve to the most recent common matrilineal ancestor from whom all living humans are descended.)
Archaeologists distinguish Homo sapiens from other hominins by a number of anatomical features, most notably a relatively slender build, a head with a large cranium (and forebrain) with a face tucked underneath this, small teeth and jaws, and a larynx situated lower in the throat. The earliest fossilized remains showing these features come from two sites in Ethiopia, and have been most recently dated as about 195,000 and 160,000 years old. The younger of these two finds includes skulls that had been deliberately polished, a mortuary practice that several scholars have interpreted as evidence of ritualizing or decoration, and thus perhaps of symbolic thought. The tools found with these skulls are not very different from those found with other hominins, however, nor are those found at other early Homo sapiens sites.
This disjuncture between anatomy and tools has led to sharp disputes among paleontologists and archaeologists about the process of human evolution at this key point. One group, including Richard Klein and Chris Stringer, asserts that although early Homo sapiens were anatomically modern, they were not behaviorally modern. Behavioral modernity, which they see as including long-range planning, rapid development of new technologies such as the bow and arrow, behaviors to deal with changing environments, wide use of symbols in burials and personal adornment, and broad networks of social and economic exchange, developed only about 50,000 years ago, in what is termed the Upper Paleolithic or Later Stone Age. At this point there was a “cognitive revolution”—sometimes dubbed the “Human Revolution” by those who take this position—a sudden flowering of creative activity within one small group that led to symbolic thought and then to everything else that is part of behavioral modernity. This may have been the result of a random, but selectively advantageous, genetic mutation that increased the mental capacity for syntactic language, allowing this group to take full advantage of changes in the vocal tract through which speech could be produced. Historical linguists such as Christopher Ehret see oral language as the key driver of this dramatic change rather than one of its results, noting that changes in vocal tract configuration and facial musculature about 70,000 years ago allowed the intricate manipulation of consonantal and vowel sounds that is human speech. (These and a few other small anatomical changes are what led paleontologists to differentiate this group as a sub-species: Homo sapiens sapiens.) Linguistic evidence suggests that human languages all descend from a small cluster of interacting languages that emerged first in Africa. Language developed in tandem with new technologies, in this point of view, and is what really allowed modern human behavior to develop.
In opposition to those arguing for a sudden and quite recent cognitive or language “revolution” are those who take more gradualist views. Among these are scholars such as Gamble who find symbolic thought evident in material objects, bodily gestures, and social relationships that long preceded speech, and those such as d'Errico who suggest that some “modern” behavior can be found among Neanderthals. The archaeologists Sally McBrearty and Alison Brooks—among others—take a slightly less expansive view, but still assert that evidence of everything labeled “behaviorally modern” emerges gradually in different parts of Africa over the Middle Stone Age, the period from about 250,000 years ago to about 50,000 years ago. For example, pieces of obsidian (a volcanic rock favored for its ability to take and hold a sharp edge) found at Sanzako in northern Tanzania in a site dating from 100,000–130,000 years ago came from more than 300 km away, suggesting that the group at Sanzako traded for this stone rather than traveling that long distance to collect it. Red ochre and ochre-stained stones on which it was ground to make pigment date from sites in Israel, Morocco, and South Africa older than 100,000 years ago (and perhaps much older). In caves near the coast of southern Africa, archaeologists have found shells with holes bored in them (suggesting they were worn as beads), stone tools that had been hardened in a fire through a multi-stage process to keep an edge better, and pieces of ochre with a cross-hatched pattern cut into them, all of which date from around 75,000 years ago. Thus there are indications of trade, long-range planning, and symbols developing separately in different parts of Africa, and then gradually assembled into the modern human cognitive and material toolkit.
Although both revolutionaries and gradualists view social and cultural matters as key markers of behavioral modernity, the gradualists (and to some degree the historical linguists) tend to see social and cultural factors as possible causes for the growth in brain complexity and symbolic thought, or at least for the better survival of hominins that exhibited this. Thus they see the development of cognition as a cultural as well as a neurological process. Some of this operated at the individual level: Individuals who had better social skills were more likely to mate than those who did not — this has been observed in chimpanzees and, of course, in humans from more recent periods — and thus to pass on their genetic material, creating what biologists term selective pressure that favored the more socially adept. For humans, being socially adept includes being able to understand the motivations of others—that is, recognizing that they have internal lives that drive their actions. Such social skills were particularly important for females: Because the period when human infants are dependent on others is so long, mothers with good social networks to assist them were more likely to have infants who survived. Cooperative child rearing required social skills and adaptability, and may itself have been an impetus to increasing complexity in the brain. Selective pressure may have also operated in the realm of language. As we know from contemporary research on the brain, learning language promotes the development of specific areas of the brain. Neurological research thus supports the argument of paleolinguists that gradually increasing complexity in language led to more complex thought processes, as well as the other way around.
Some of these social and cultural factors operated at the group level: As it developed, speech and other forms of communication allowed for stronger networks of cooperation among kin groups and the formation of larger social groupings. Family bands that were more socially adept had more contacts with other bands, and developed patterns of exchange over longer distances, which, as with trade in later periods, gave them access to a wider range of pro
ducts and ways of using them and thus greater flexibility to meet any challenges to survival, including dramatic changes in climate. This was also the case with less utilitarian products, such as pigments and beads, which might have stimulated better forms of communication and higher levels of creativity as well as reflecting these. As Marcia-Anne Dobres and others have pointed out, new technologies and ways of using them were (and are) invented not simply to solve problems or address material needs, but also to foster social activities, convey world views, gain prestige, and express the makers’ ideas and sense of identity.
At the moment, the archaeological record, particularly of human remains, in Afroeurasia for the key period from about 100,000 to about 50,000 years ago is sparse. Further research in many fields—including neurology, comparative linguistics, and genetics as well as archaeology—will no doubt provide firmer support for the revolutionary or gradualist perspective, or perhaps allow them to be combined.
A Concise History of the World (Cambridge Concise Histories) Page 4