By looking at 400 bones from 2.5 million years ago, paleoanthropologists can tell how rocks were used as some of the first tools to butcher and process meat and marrow processing of large carcasses. It's a clue that carnivory has been part of hominid evolution for at least 3 million years.
Environment and Behavior of 2.5-Million-Year-Old Bouri Hominids
The Hata Member of the Bouri Formation is defined for Pliocene sedimentary outcrops in the Middle Awash Valley, Ethiopia. The Hata Member is dated to 2.5 million years ago and has produced a new species of Australopithecus and hominid postcranial remains not currently assigned to species. Spatially associated zooarchaeological remains show that hominids acquired meat and marrow by 2.5 million years ago and that they are the near contemporary of Oldowan artifacts at nearby Gona. The combined evidence suggests that behavioral changes associated with lithic technology and enhanced carnivory may have been coincident with the emergence of the Homo clade from Australopithecus afarensis in eastern Africa
We collected 400 vertebrate fossil specimens from the Hata Member (Table 1). Almost all of these come from within 3 m of the MOVT; most were found immediately above this unit. This assemblage largely reflects a mixture of grazers and water-dependent forms, which is broadly typical of later hominid-bearing Plio-Pleistocene occurrences and consistent with the sedimentological interpretation of the deposits as primarily lake marginal. Alcelaphine bovids are abundant and diverse. All indicators point to a broad featureless margin of a shallow freshwater lake. Minor changes in lake level, which were brought about by fluctuating water input, would probably have maintained broad grassy plains leading to the water’s edge. As discussed below, hominids were active on this landscape.
The bone modifications at these two excavated localities and at other localities from the same stratigraphic horizon across .2 km of outcrop demonstrate that stone tool–wielding hominids were active on the lake margin at 2.5 Ma. The bone modifications indicate that large mammals were disarticulated and defleshed and that their long bones were broken open, presumably to extract marrow, a new food in hominid evolution with important physiological, evolutionary, and behavioral effects. Similar patterns of marrow acquisition have been reported for younger sites such as Koobi Fora and Olduvai Gorge (12).
The situation on the Hata lake margin was even more difficult for early toolmakers. Here, raw materials were not readily available because of the absence of streams capable of carrying even pebbles. There were no nearby basalt outcrops. The absence of locally available raw material on the flat featureless Hata lake margin may explain the absence of lithic artifact concentrations. The bone modification evidence demonstrates that early hominids were transporting stone to the site of carcass manipulation. The paucity of evidence for lithic artifact abandonment at these sites suggests that these early hominids may have been curating their tools (cores and flakes) with foresight for subsequent use. Indications of tool curation by later hominids have been found at the more recent Pleistocene sites of Koobi Fora [Karari escarpment versus Ileret (13)] and Swartkrans [polished bone tools in a single repository (16)]. Additional research into the Hata beds may allow a determination of whether the butchery is related to hunting or scavenging. The Bouri discoveries show that the earliest Pliocene archaeological assemblages and their landscape patterning are strongly conditioned by the availability of raw material. They demonstrate that a major function of the earliest known tools was meat and marrow processing of large carcasses. Finally, they extend this pattern of butchery by hominids well into the Pliocene.