Behavioral influences
The story of hominin evolution is one of increasing behavioral complexity, but, because behaviour does not leave direct fossil evidence, clues must be sought in other sources. The most obvious candidates are in the archaeological record, which has traditionally begun with the appearance of Paleolithic (Old Stone Age) tools about 2.5 mya. (See also Stone Age); however, that date is complicated by the discovery of tools in 2015 that date back to 3.3 mya. Early tools were simple indeed: stone flakes a few centimetres long that were chipped off of one small cobble by a blow from another. But, for all their simplicity, they marked a major advance in lifestyle: for the first time, the carcasses of dead animals could be dismembered quickly, and favoured parts could be taken for consumption to safer places, where blows from hammerstones allowed the extraction of nutritious marrow from bones. These tools also signify a cognitive advance in hominins; even with intensive training, no ape has yet mastered the notion of hitting one rock with another at precisely the angle needed to detach a sharp flake. Furthermore, the early toolmakers had the ability to anticipate their needs, since they often carried suitable rocks long distances before making them into tools.
The history of stone toolmaking ushers in a pattern seen throughout the paleoanthropological record until the emergence of behaviorally modern H. sapiens: in general, technological innovations have been sporadic and rare. Moreover, behavioral novelties have tended not to coincide with the appearance of new species. For almost a million years following the introduction of stone tools, the methods used for making them remained largely unchanged. It is only after about 1.8 mya, in Africa (well after the appearance of Homo ergaster), that a larger type of tool is introduced: the hand ax. Shaped carefully on both sides to a standard and symmetrical form, it was usually teardrop- or egg-shaped. It is the characteristic tool of the Acheulean industry. Although the notion has been contested, it does seem fairly clear that these implements bear witness to another cognitive advance: the existence in the toolmaker’s mind of a standard “mental template” to which the tools were made. Hand axes were manufactured in Africa by the thousands—sometimes at apparent workshops—until quite recent times. Stone tools of this kind have always been rare in eastern Asia. It is only at about 300–400 kya that another major technological (and possibly cognitive) advance is found. This is the “prepared-core” tool, whereby a stone core was elaborately shaped until a single blow, perhaps with a hammer made of a “soft” material such as bone, would detach a virtually finished tool with a continuous cutting surface around its periphery. The great masters of this technique (see also Mousterian industry) were the Neanderthals, whose possession of language has long been debated. Regardless, it has been demonstrated (in studies with people) that language is not required for the transmission of the skills needed to make tools of this kind.
The stone tool record is well-preserved, but it is only an indirect reflection of overall lifestyle and cognitive capacities. It is still unknown, for example, whether the earliest tool users hunted extensively or merely scavenged animal remains. It is likely that, if they hunted, it was for small prey. Nonetheless, metabolic studies of bone suggest that some Australopithecus may have eaten substantially more meat than chimpanzees do today.
Most authorities had guessed that efficient ambush hunting was an invention of H. sapiens, but 400,000-year-old wooden throwing spears found in 1995 at Schöningen, Germany, may suggest otherwise. Unlike thrusting spears, which must be used at close range and with considerable risk, these 2-metre (6.6-foot) javelin-like weapons have their weight concentrated at the front and therefore could have been hurled from a safe distance. The age of the location at which these spears were found puts them within the period of H. heidelbergensis.
Also at 400 kya there is the first convincing evidence of two other innovations: the domestication of fire in hearths and the construction of artificial shelters. At Terra Amata in southern France, traces of large huts have been found. The huts were formed by embedding saplings into the ground in an oval and then bringing their tops together at the centre. Stones placed in a ring around the hut braced the saplings. Some of these huts were found to contain hearths scooped in the ground and lined with burned stones and blackened bones. These sites represent some of the earliest definitive proof of fires deliberately maintained and used for cooking, although nearly 800,000-year-old hearths are reported from a site in Israel.
Prior to the advent of H. sapiens, archaeological sites are generally random scatterings of detritus of various types—mostly butchery sites and sites where groups lived at later times. In the dwelling places of behaviorally modern early H. sapiens, on the other hand, there is a definite pattern in the use of space: toolmaking was done in one place, cooking in another, sleeping elsewhere. The earliest intimations of such partitioning are found at the South African site of Klasies River Mouth, dating to more than 100 kya. This pattern is also typical of sites left behind by the earliest European H. sapiens, who colonized that continent many tens of thousands of years later. Although the first evidence of symbolic thinking, which appears to have predated H. sapiens, was discovered on the island of Java in 2014 in the form of a zigzag shape etched on a shell dated to some 450 kya, the African sites serve as the earliest evidence of symbolism and the complex behaviours that characterize H. sapiens worldwide today. At Blombos Cave, near Africa’s southern tip, was found an ochre plaque more than 70,000 years old that is engraved with an unmistakably geometric motif. This and other early African sites have produced engraved ostrich eggshells and snail shells pierced for stringing and bodily adornment; these date from 70 to 50 kya. It is also in Africa that the earliest evidence appears for such modern behaviours as long-distance trade and the mining of flint for artifact production.
The most-striking evidence for a distinct cognitive contrast between modern humans and all their predecessors, however, comes from Europe. H. sapiens came late to this continent and brought a new kind of stone tool based on striking long thin “blades” from a carefully prepared long core. These Aurignacian tools, which were probably developed in Africa some 75,000 years ago, were accompanied by a kit of implements that for the first time were made out of materials such as bone and antler and that were treated with exquisite sensitivity to their particular properties. In short order these Europeans, the so-called Cro-Magnons, left a dazzling variety of symbolic works of prehistoric art. The earliest known sculptures—delicate small carvings in ivory and bone—are about 34,000 years old. From about the same time come the earliest musical instruments, bone flutes with complex sound capabilities. Also from this time, roughly 25,000 kya, come the first known notations. These markings were made on bone plaques, one of which has been interpreted as a lunar calendar. By 30 kya the Cro-Magnons were already creating spectacular animal paintings deep in caves, most of which are accompanied by numerous geometric symbols (see also Eyzies-de-Tayac; Lascaux Grotto; Font-de-Gaume; Altamira).
Domestic items were regularly decorated and engraved by the Cro-Magnons. Burials, already practiced by the Neanderthals in a simple form, became complex, and graves were often crammed with goods that were likely thought to be useful to the deceased in an afterlife. Clay figurines were soon baked in primitive but remarkably effective kilns, and by about 27 kya delicate eyed needles made of bone heralded the advent of couture (garment making). It is hard to ask for better proof that the Cro-Magnons were modern H. sapiens cognitively equipped with all the intellectual faculties of today’s people. Nobody would dispute, for example, that the Cro-Magnons had language; such a claim is arguable in earlier Stone Age H. sapiens and Neanderthals.
The Cro-Magnons contrasted strikingly with the Neanderthals, the hominins they had found already living in Europe upon their arrival and whom they replaced entirely over the next 10,000 to 12,000 years. While symbolic behaviours are typical of all groups of living humans, not all such groups have left behind symbolic records as dramatic as those of the Cro-Magnons. Nonetheless, there is no doubt that the Cro-Magnons and the Neanderthals perceived and interacted with the world in entirely different ways. The Cro-Magnons were people with whom present-day humans could relate on their terms, and, as such, H. sapiens is not simply an incremental improvement on previous hominins. As the archaeological record eloquently indicates, our species is an entirely unprecedented phenomenon.
Exactly when and where this new phenomenon initially occurred is problematic, but again the earliest evidence for the new behavioral pattern comes from Africa, and, as is discussed in the section below, the earliest anatomic intimations for the origin of H. sapiens also come from that continent. However, anatomic and cognitive “modernities” do not seem to have developed hand in hand; evidently there was a time lag between the establishment of modern anatomy (which appears to have come first) and modern behavioral patterns. While perhaps counterintuitive, this observation actually makes sense. Any innovation must take place within a species, since there is no place else it can do so. Natural selection is, moreover, not a creative force. It merely works on variations that come into existence spontaneously; it cannot call innovations into existence just because they might be advantageous. Any new structure or aptitude has to be in place before it can be exploited by its possessors, and it may take some time for those possessors to discover all the uses of such novelties. Such seems to have been the case for H. sapiens in that the earliest well-documented members of our species appear to have behaved in broadly the same manner as Neanderthals for many tens of thousands of years. It is highly unlikely that another species anatomically indistinguishable from H. sapiens but behaviorally similar to Neanderthals was supplanted worldwide in an extremely short span of time. Therefore, it seems appropriate to conclude that a latent capacity for symbolic reasoning was present when anatomically modern H. sapiens emerged and that our forebears discovered their radically new behavioral abilities somewhat later in time.
A cultural “release mechanism” of some sort was necessarily involved in this discovery, and the favoured candidate for this role is language, the existence of which cannot be inferred with any degree of confidence from the records left behind by any other species but our own. Language is the ultimate symbolic activity, involving the creation and manipulation of mental symbols and permitting the posing of questions such as “What if?” Not all components of human thought are symbolic (the human brain has a very long accretionary, evolutionary history that still governs the way thoughts and feelings are processed), but it is certainly the addition of symbolic manipulations to intuitive processes that makes possible what is recognized as the human mind.
The origins of this mind are obscure indeed, especially as scientists are still ignorant of how a mass of electrochemical signals in the brain gives rise to what present-day humans experience as consciousness. But the invention of language would plausibly have released the earliest of the cultural and technological innovations that symbolic thought makes possible—in the process unleashing a cascade of discoveries that is still ongoing. One of the most-striking features of the archaeological record that accompanies the arrival of behaviorally modern H. sapiens is a distinct alteration in the tempo of innovation and change. Significant cultural and technological novelties had previously been rare, with long periods of apparent stability intervening between relatively sudden episodes of innovation. But once behaviorally modern H. sapiens arrived on the scene, different local technological traditions—and, by extension, other forms of cultural diversity—began to proliferate regularly, setting a pace that is still gathering today.