advent-of-hominins-day-ten-ARA-VP-12/130

ARA-VP-12/130

This specimen, found by Haile-Selassie in 1997 in Afar depression, Ethiopia, is described in a paper by Berhane Asfaw and colleagues in 1999. It consists of cranial fragments from the frontal, parietals, and the maxilla with much of the dentition.

As you can see, the lower part of the face is fairly prognathic. The cranial capacity is ~450 cm3 and the cranium has marked post-orbital constriction, in which the part of the skull behind the eyes is narrowed. The dental arcade is U-shaped, rather than the more parabolic shape seen in modern humans. The image below (from Asfaw et al 1999) compares an (a) A. afarensis and (b) A. boisei palate to that of A. garhi. Note that for the photo of BOU-VP-12/130 they mirror-imaged on midline to compare to the other fossils.

Based on its size, the cranium is assumed to be a male but this is hard to know for sure. The skull & teeth differ from Autralopithecus genera known from East Africa. For example, it has large molars (as big, or bigger, than seen in robust australopiths) and lacks the morphological suite known for the robust australopiths. For this reason, scientists set this fossil as the type specimen for Australopithecus garhi

Other fossils found nearby, including cranial & limb fragments may also fit into this species. Interestingly, one femur (BOU-VP-12/1A-G) has cutmarks on it left by stone tools. However, it isn’t clear if the postcranial bones can be attributed to A. garhi. That being said, the postcrania show a humanlike humeral/femoral ratio, which may be the earliest known appearance of the relative femoral elongation that characterizes later hominins. It retains a bracial index that is indicative of an ape. This may suggest, contra other work, that hominin’s femora got longer before the forearm shortened.

At the time these fossils were announced the most shocking and surprising claim was that the fossils were found ‘associated’ with cutmarked faunal bones. During surface collection of material within the locality that BOU-VP-12/1 was found, several mammal bones were found that have cut marks & percussion marks made by stone tools. Moreover, stone tools from the nearby Gona site dating to 2.6 mya were also uncovered. This was shocking since at the time many paleoanthropologists thought that only members of the genus Homo could make stone tools. Nowadays I think this hypothesis is, while not completely falsified, very much in doubt. A few years back we learned of the Lomekwian tradition, which dates to 3.3 and also suggests that stone tool production predates our genus.

Of course, it may be that Homo is earlier and we just aren’t finding examples of it. Also, many non-human species use tools and some even use stones to crack open nuts.

These pre-Homo technologies are an indication that maybe other species of hominins were innovating and creating new ways to be human (or human-like). Some of these techniques may have never become part of the human niche, but others may have had a significant, but unknown, influence in the processes of becoming human.