7. The Evolution of Hominids

7.4 Homo Erectus

Homo erectus, the Pithecantrop, originated in Africa. Remains dating 1.8 million years, together with simple “Oldowan” stone tools, have been found in Tanzania (Olduvai Gorge). In Kenya (Turkana), a date of 1.9 million is plausible. This early species of H. erectus, sometimes called H. ergaster, had a braincase inferior to 800cc and was of a small size. Very rapidly, the species expanded. Representatives of this early H. erectus sensu lato species were found in the Republic of Georgia (Dmanisi) 1.7 million years ago10.

Until the find of Dmanisi, the fossil evidence was that early humans did not journey out of Africa until they could walk long distances and were smart enough to invent sophisticated tools: these traveling hominids supposedly had to have big brains and long limbs. Three Dmanisi skulls have been discovered, associated with primitive stone tools, which suggest that our ancestors left Africa at an earlier stage of evolution. One skull has a cranial capacity of just 600 cubic centimeters11 (cc), compared to 650 cc and 780 cc for the other two skulls, and is thus substantially smaller than expected for Homo erectus. Modern human braincases are about 1400 cc. These three skulls tend to indicate that the discovered group is intermediary between H. erectus and H. habilis. Thus, the Dmanisi hominids might be descended from primitive H. habilis ancestors, which had already left Africa. A heretical further possibility is that H. erectus itself evolved outside Africa, still considered the cradle of human evolution.

From there, the dispersal took momentum and members of the species went East and were found in Java (putatively 1.8 million years) and in China (Longgupo Cave – 1.9 million years but the bones are doubted to be human- and Gongwanling 1.1 million years), with a concurrent evolvement of the species into H. erectus sensu stricto. H. erectus sensu stricto was found only much later in Italy (Ceprano, 900,000 years), Spain (Atapuerca 780,000 years) and France (Tautavel, 450,000 years). The speed of its expansion toward the East, backed with such primitive tools as stone flakes, scrapers and chopping tools, and the late expansion in Europe, is puzzling.

The next oldest undisputed traces of early humans outside Africa are primitive tools found at Ubeidiya, Israel, dated to be as early as 1.5 million years. These tools, which appeared in Africa 1.6 million years ago, are of a primitive Acheulean type, which includes hand axes and other tools carefully crafted according to a preconceived plan. The evolved Acheulean technology was rarely seen outside Africa until about 500,000 years ago and this lack of expansion is difficult to understand, compared with the success of the Oldowan toolmakers. The early age and primitive Oldowan technology of the Dmanisi site indicate that the initial hominid dispersal out of Africa was driven by biological and ecological parameters, not technological innovations. The drive was probably the urge to fulfill the increasing energy requirements of larger body sizes, perhaps met by a greater exploitation of animal protein.

The question, facing these different tools and fossils, is if they were members of one single species, H. erectus, which included later fossils in China and Indonesia, or did they belong to two different species, the second one called H. ergaster. Was H. ergaster the human ancestor, and H. erectus an Asian dead end? A million-year-old skull from Ethiopia dug up in 1997 tends to settle the case in favor of only one single species, H. erectus, because this skull shares key features with both the early African and the somewhat later Asian and African fossils and, therefore, links them all as interbreeding members of the same wide-ranging species that gave rise to living humans. There was apparently one single species that spread from Africa to Europe to Asia 1 million years ago, rather than several different species alive at once.

A human species, Homo antecessor, dating about 800,000 years ago, has been dug up in Northern Spain, at Atapuerca, that is believed by some scientists to be the common ancestor of modern humans and Neanderthals. Cut marks on bones of 800,000-year-old H. antecessor show that the inhabitants of the cave were feasting on human flesh.

7.4.1 Brain size increase

A second brain surge, linked to the Pithecanthropus, occurred 500,000 years ago and increased hominid brain size by another 75%, bringing it close to the 1300-1500 cubic centimeters of today.

The skeletons of Pithecanthropus or Man-Apes or Homo erectus are associated with the use of fire. Whereas the skeletons of the Australopithecines are rare, those of the Man-Apes are found in relative abundance from Peking to the shores of the Atlantic, in Casablanca or in Heidelberg. They had formidable jaws and a flat forehead with teeth quite similar to those of modern man. Despite the bestiality of the face, their skeleton was remarkably modern. However, whereas the cranial cavity of modern man is about 1,350 ml, the brain size of the first Pithecanthropus found in Java is 900 ml, which is 10% less than that of the more tardy variety of Pithecanthropus that appeared in China, whose brain size was about 1,000 ml. Thus, human anatomical features were gained before the brain acquired a size above the level of the great apes.

It does not seem that a structured language as we know it, based on at least five vowels and a number of consonants, was possible for any hominid, including Neanderthal, because of an adverse mouth configuration. However, socializing and group activities were necessities for Pithecanthropic hunters if they were to succeed in their enterprises and we can assume that some sort of language was in use. This would reinforce the need for a larger brain. Bipedal locomotion had required the transformation of the pelvis, so that the full weight of the body could be carried on it. As a consequence, the female birth canal decreased in size, which was of no consequence as long as the babies were small. In order to accommodate to the need for an increased cerebrum, the hominid fetus must then have begun to be delivered at earlier stages of development so that the nervous central system could continue to develop after parturition. The baby becoming thereby more dependent, the need to care for it has patterned the whole social development of the hominids. The community life must have been slowly reinforced and this in turn created another need for a bigger brain. Such brains allowed then the use of tools that again were a stimulus for a better development of the brain.

Haim Ofek12 argues that the increase in size of the brain that occurred around that time may be traced to market trading. Market trading meant more than sharing food with the family. It involved distinct commodities, relative prices and a precise reckoning of relative values. Division of labor allowed specialization, in tool-making, in fire keeping, without starving. This specialization allowed new kinds of resources to be exploited. Long distance trade may have reduced the likelihood of speciation by encouraging contact among different tribes. This idea that market trading and competition led to a dramatic increase in brain size challenges the paradigm on which this essay is developed: namely that biology is built on the more fundamental sciences of physics, chemistry, biochemistry and molecular biology, and is itself a building block for the more human social sciences, philosophy and theology. If economy specifies anatomy, then the social sciences, considered an achievement constructed on the more fundamental sciences, become themselves a building block of biology!

7.4.2 The refinement of the tools

7.4.2.1 The chopping tools

The Sinanthropus, i.e. the Chinese variety of Pithecanthropus (Homo erectus of China) was using tools of a very primitive character: the chopping tool. The use of tools is not restricted to man: chimps hurl clots of earth at enemies and use sticks, some insects close their nests with pebbles and cephalopods insert stones between the valves of mussels. The fabrication of stone tools as opposed to the use of tools is by no means easy and requires a good development of the hands, the eyes and the brain. Homo erectus had reached such a stage. The chimpanzee that prepares the sticks he plunges in termites’ nests also reaches this stage.

7.4.2.2 Bifaces

Bifaces appeared 1.5 million years ago. More refined bifaces originated about 500,000 to 350,000 years ago in Kenya, probably in a forested environment (fig. 7.4). From Africa, the use of the Kenyan bifaces expanded to Europe and the Near East.

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Figure 7.4. The Kenyan biface tools are more refined than the chopping tools. In this instance, the maker often shows more interest in the flakes than in the core of the worked cobble.

The Kenyan stone tools initially produced were made in a very crude and rustic way. A progressive refinement in the manufacture of these bifaces took place in the course of the ages. The tools evolved towards specialization with a greater cutting ability of the instruments and a greater economy of means in their preparation. The cutting tools were produced by chopping off flakes from a silex to create an irregular cutting edge on the nucleus. The residual flakes that present a regular edge were used as scraping tools.

7.4.2.3 Flakes

The Kenyan biface made by detaching flakes from the two flat sides of a silex in order to produce a bifaced hammer, was perfected over 200,000 years. It reached a new step 150,000 years ago, during the Riss glaciation. It was a product of the Levallois industry (fig. 7.5).

Figure 7.5. The Levallois point is an elegant product whose symmetry shows the high intelligence of the artisan. The Mousterian point is even more refined and, in this case, beauty is added to the product.

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In the Levallois culture, the flakes became decidedly more important than the nucleus of the worked stone. This improvement and refinement of tools was probably accompanied by a refinement of the physical aspect of the men making the tools.

During this immense period of time that saw the evolution of the first hominids, there is not the slightest evidence of utilization of bows and arrows. A bow allows the penetration and hunting into forests and also allows individual hunting. In its absence, the whole operation of hunting must have rested on the concerted action of a group that used traps and probably also fire extensively. Elephants, rhinos, aurochs, buffaloes, horses, boars and deer were hunted together with carnivores such as the saber-toothed tiger, the hyena, the leopard and Homo pekinensis himself. The Pithecanthropus had thus reached a good stage in the development of man’s evolutionary trend as a hunter of great herbivores and other mammals, as is still exemplified by the hunting habits of Stone Age people such as the pygmies. The pygmies follow an elephant during 2 to 3 days, and harass it. Once the animal is exhausted, they crawl under it and pierce its belly with stakes.

By 200,000 years ago, the sociability of the pre-Neanderthals had so much improved that the group took care of the disabled and sick.

Homo erectus used fire. This step took over 4 million years to be accomplished and is very important because it denotes an ability to dominate a natural element and bears the promise of still greater achievements. Yet, the Pithecanthropus was doomed. At the end of the middle Pleistocene period, about 120,000 years ago, a drastic climatic perturbation took place. The Sahara region dried up and the place most favorable for the development of the bifaces turned into a desert. The desert cut the African continent out of the great cultural exchanges. Diverse retardate provinces that evolved along two local lines kept the tradition of the Kenyan bifaces there. One of these was maintained until 3,000 years ago while the other is still pursued now in South Africa. Stone blades are also still produced now in the Turkish village of Cakmak from locally quarried nodules of flint.

7.4.3 Verbal skills

Within the Pithecanthropic evolving line, one may discern two anatomical specializations correlating with two distinct evolving trends. One trend perfects masticator abilities and ultimately results in the Neanderthal dead-end. The other perfects verbal communication. Two hundred thousand years ago, the African hominids had cranial bases identical to those of modern humans. The larynx had descended, which offers no benefits other than easier speech and, 100,000 years ago, modern speech became possible. The Man from Broken Hill must be 100,000 years old and is morphologically more evolved than the Pithecanthropine prototype, without being Neanderthal. The vocal canal of the Man from Broken Hill is able to produce acoustic signals reminiscent of the vowels (a), (i) and (u). These vowels are the clearest, stablest, least ambiguous, best understood sounds produced in a human language and the hominids who could produce these sounds would have a slight selective advantage over those who could not. This was still not the case for the late Pithecanthropus represented by the Man from Broken Hill. Although on their way to reach this achievement, they were not quite able to pronounce these sounds clearly. At that level, selective advantages due to the refinement of communication may not have surpassed the advantages due to a greater efficacy in mastication. They were perhaps even less advantageous because of a slight impairment of the respiratory function. Selective pressures favoring better mastication produced the Neanderthal.

References

10. L. Gabunia et al. Earliest Pleistocene Hominid cranial Remains from Dmanisi, Republic of Georgia. Science 288, 1019-1025, 2000

11. A. Vekua et al: A new skull of an early Homo from Dmanisi, Georgia. Science 297: 85-89, 2002

12. Second Nature. Economic origins of human evolution. Cambridge U.P. Cambridge, 2001

13. in the 1995 issue of the Proceedings of the National Academy of Sciences : 92, 6720-6722=

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