A105 Lectures 20 & 21, 2001
Archaeological Record of Early Hominids
The earliest archaeological record consists of stone artifacts, flaked with conchoidal fracture, sometimes showing evidence of use (edge damage, use-wear). These broken stones are recognizeable as artifacts because they occur away from natural sources of stone, so they must have been carried to the sites artificially (e.g. by hominids). They often occur in concentrations with fossils animal bones, which sometimes are broken open. This can be thought of as the world's oldest garbage...
The earliest sites now known come from the Rift Valley of East Africa. The Gona site in the Hadar region of Ethiopia is the best dated early site and is 2.6 million years old. Other sites older than 2 million years have been found in southern Ethiopia (Omo) and on the west side of Lake Turkana in northern Kenya. Many sites are known that date between 2 and 1.5 million years old from around Lake Turkana (e.g. Koobi Fora sites, such as site 50, shown in your section video) and Tanzania (e.g. Olduvai Gorge sites described in your textbook).
Which hominid made these stone tools and was responsible for the debris? Most archaeologists assume that Homo habilis (and/or Homo rudolfensis) made many, if not all, these tools, because of its larger brain size and smaller teeth, more gracile chewing musculature. The only problem with this argument is that the oldest stone tools now predate the oldest fossil evidence of Homo by over 250,000 years. Perhaps this is just sampling error... However, it has been argued that the robust australopithecines would have had the manual dexterity to flake stones in this way as well. And since chimps can make and use tools with smaller brains than any hominid it seems difficult to argue that stone tool flaking was beyond the mental capacity of robust australopithecines. However, , stone tools continue to be made even after the australopithecines go extinct, so it seems likely that early Homo made at least some of the flaked stone tools.
A recent set of fossil finds has added a new twist to this argument. As described in the article in your reader, a new species, Australopithecus garhi, has just been described from a site called Bouri, in Ethiopia, that is contemporary with the first know stone tools. Not only that, but nearby were found several animal bones scored with cutmarks made by stone tools. Was A. garhi the "butcher of Bouri" and the maker of the first know stone tools? A. garhi has a small brain and extremely large cheek teeth and chewing muscles, yet it doesn't have the same massive, robust face that was typical of the robust Australopithecines. Perhaps it was supplementing a vegetarian diet with more soft foods, like meat and marrow, obtained using the stone tools? Only time will tell.
These sites with stone hammerstones, flaked cobbles and flakes are called Oldowan technology sites, named after Olduvai Gorge. The technology was simple, but effective for cutting and smashing and chopping a wide range of materials, including wood, soft plant material and bones and meat. Tools give you access to things beyond your anatomical capabilities, which is why California sea otters crack open molluscs with stone anvils, and why chimps use a variety of tools to get foods. What were the Oldowan tools used for? Little evidence of use wear is diagnostic for these early tools, though Larry Keeley has argued that some flakes from Koobi Fora were used on various plant materials, as well as meat cutting. Stone tool cutmarks and percussion marks on animal bones at many of the early sites are good evidence linking the hominids to the animal bones, suggesting that the early tool makers ate meat and marrow from the carcasses of animals larger than any killed by chimps. Did hominids KILL these large mammals? Hard to say.... few complete carcasses found at sites, and many of the bones also have carnivore toothmarks on them. Archaeologists like Rob Blumenschine have argued that scavenging would have been a viable option for early hominids. They could have used sharp stone flakes to steal bits of carcasses away from carnivore kills, to eat them in safety away from the kill sites. Or, as Blumenschine demonstrates in the video, hominids could have found cached leopard kills to get access to meat as well as marrow.
Early Homo would have needed a reliable source of both calories and protein to support the growth and development of their relatively large brains. The appearance of the first Homo erectus specimens in East Africa, at Lake Turkana, dated to 1.9 million years ago, makes this even more likely, since these guys had larger brains (850cc+) than previous Homo, as well as smaller , more gracile faces, smaller molars, and smaller chewing muscles, suggesting a soft, high-quality diet.
They were also big, and the Nariokotome skeleton "Turkana Boy" from West Turkana (WT 15000) (often called Homo ergaster) was tall and thin, adapted for staying cool while walking long distances in hot, dry climates. The brain size of these early Homo erectus individuals was so large, and their hips so narrow, that they probably gave birth to very immature offspring, compared to earlier hominids. Note that apes and all other animals give birth to infants with 50% of adult brain weight, whereas modern human babies are born with brains only 25% their adult size. Nariokotome boy's girlfriend could not have given birth to an infant with a brain more than 30% its adult size... suggesting a very dependent offspring. Additionally, the sexual dimorphism in body size and skeletal morphology seems much reduced in these early H erectus individuals, suggesting that they were less involved in physical competition for mates... Perhaps they used their brains, rather than their brawn, to win over the opposite sex? Some anthropologists feel that this is evidence for pair bonding mating patterns in Homo erectus, which would fit neatly with the home base & food sharing interpretation of early sites proposed by Glynn Isaac (reviewed on video in sections).
New technologies of Homo erectus:
Between 1.9 and 1.5 million years ago, Homo erectus continued the Oldowan technology of its predecessors. But around 1.5 million years ago we find evidence for two types of technological innovation:
Note that Homo erectus is the first hominid to leave the African continent and colonize parts of southern Europe and Asia. Current evidence makes it likely that this had occurred before 1.5 million years ago (before Acheulian technology was invented), perhaps explaining why many early Eurasian sites contain only Oldowan-style core and flake tools, rather than handaxes. See the article by Roy Larick and Russ Ciochon that discusses this evidence.
WWW links to descriptions and images of early Hominid Fossils and Early Archaeology:
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