Garhi (which means surprise in the Afar language) was a hominid species that existed in eastern Africa 2.5 million years ago. The fossils were first discovered at the Bouri Formation in Ethiopia by Y. Haile-Selassie in 1997, and consisted of two partial skulls, two mandibles (one mostly complete) and pieces of femur, humerus, radius and ulna. The remains are indeed surprising because very few fossils are found that date from 3.0 to 2.0 million years ago.
Cranial capacity: 450 cc
A. Garhi fossils exhibit a mixture of primitive and advanced traits. The species had a very prognathic face, small cranial vault and long, ape-like arms in relation to overall body size much like A. Afarensis. There was a sagittal crest (indicating large jaw muscles). At the same time, the thigh bone had lengthened to a more Homo-like proportion. The structure of the limb bones appears to be an intermediate between that of A. afarensis and H. ergaster.
The dentition of A. Garhi also reflects this mix of traits. The canines protruded and there was a diastema between the lateral incisor and the canine – again, features shared with Australopithecus Afarensis. At the same time, the anterior molars were larger than any other hominid species outside of Paranthropus boisei. The second molars were larger than any Homo, but the size ratio of molars to incisors was more like Homo than any Australopithecine.
This species in many ways straddles the line between Australopithecine and Homo, making it a good candidate for the missing link in our direct ancestry. The date of Garhi corresponds to time period in which researchers believe that a transition to a more modern hominid occurred. Also, the mixture of dental traits in this species could point to a diet that was changing from basically vegetarian fortified with grubs to a diet that included more meat.
This addition of meat in the diet may have played a key role in the development of larger brains because meat provided more fat and calories in a smaller amount of food allowing for the excess energy needed for the change in brain size. This may have been one of the catalysts in the development of more modern hominid intelligence in Australopithecus garhi.
The fossils in Ethiopia were found in conjunction with traces of animal butchery (using crushing stones and scrapers). Animal bones found at the same site had clearly been notched with stone tools, but there is no way to tell if the butchering had been done by the Garhi individuals. If the Garhi are proven to be the tool-users, this is the earliest evidence of tool usage that can be linked to a particular species.
At this time there is no conclusive evidence that Australopithecus garhi walked with a more modern gait, used tools or even was an direct ancestor of modern humans. The current fossils do not disprove these assumptions either, but it is unwise to base conclusions about a proposed population on fossil remnants of only a few individuals. More fossil evidence is needed before any definitive answers can be discovered.