After There was 'Lucy'
New 2.5 million-year-old ancestor found in Ethiopia
2.5 million-year-old fossils
Earlier this year, a team of Ethiopian, American, and Japanese researchers announced their discovery of the cranial and tooth remains of a previously unknown hominid that may be a direct human ancestor and an evolutionary link between the ape-man of Africa, Australopithecus (“southern ape”), and the genus Homo (“man”).
The 2.5-million-year-old fossils were unearthed between 1996 and December 1998 outside the Afar village of Bouri, in the desert region of Ethiopia called the Middle Awash. The new species was named Australopithecus garhi. The word “garhi” means “surprise” in the Afar language.
In addition to the garhi fossils, the team also found the arm and leg bones of several other hominid individuals in the same geological layer. Although they cannot be reliably assigned to A. gahri or another species, their relative limb proportions are between those of apes and humans.
Long forearms, human-like legs
While the famous “Lucy” fossil (3.2 million years ago) had upper arms that were long relative to her legs, and Homo erectus, “upright man” (1.7 million years ago) had the shortened forearms and the longer femurs of modern humans, these new unidentified primates had an intermediary set of limbs: long forearms and human-like legs. This indicates that the thighbone (femur) lengthened at least one million years before the forearm shortened.
These bipedal creatures used stone tools to fillet meat and scrape marrow from large animals, the earliest known evidence of animal butchering with stone tools, which marks the transition from a heretofore strict vegetarian diet to a carnivorous one. This “dietary revolution” opened up a whole new world of food and may have paved the way for emigration out of Africa to new habitats and continents.
Analyses of the A. garhi fossils show mixed traits that sharply distinguish them from the “Lucy” species Australopithecus afarensis (southern ape of Afar) and the other hominid species known to be alive around the same time.
Ancestors to modern humans
The new species' braincase, face, and palate are more primitive than Homo and lack the specialized cranial characters of the robust ape-men of eastern and southern Africa. Its features are most like its ancestor A. afarensis. The face projects forward, the braincase is crested and small, but the premolars and molars are enormous. This combination of features has never been seen before and scientists say that it is very possible that A. garhi was the direct ancestor of Homo, which includes modern humans.