Human ancestors may have used tools much earlier than previously believed. Findings of a new study reveal that the ape-looking members of the human family tree may have been capable of using tools over 3 million years ago, or about half a million years earlier than the oldest stone tools discovered.
The study, which was published in the journal Science on Jan. 23, challenges the assumption that the Homo habilis, also known as the Handy Man, was the first to craft stone tools. Scientists traditionally believe that this species, which lived 2.4 million years ago, pioneered the use of stone tool in human lineage.
Tracy Kivell from Britain's University of Kent, together with colleagues, analyzed bones from the hands of the Australopithecus africanus, a hominid characterized by a combination of ape and human features that thrived in the Pliocene Epoch about 5.3 to 2.6 million years ago. The now extinct species had foot and leg bones that allowed them to walk upright and long arms that suited them for tree climbing.
Kivell and colleagues found that these early members of the human family tree had human-like hands that allowed for precision grips, such as when one is turning a key, and squeezing or power grips, such as when one is wielding a hammer or holding small objects with the aid of the opposable thumb.
The researcher said that because forceful precision grips are associated with tool making and the use of stone tool, it is possible that the A. africanus also used stone tools.
"Here we show that Australopithecus africanus (~3 to 2 million years ago) and several Pleistocene hominins, traditionally considered not to have engaged in habitual tool manufacture, have a human-like trabecular bone pattern in the metacarpals consistent with forceful opposition of the thumb and fingers typically adopted during tool use," the researchers wrote in their study.
The trabecular bones that the researchers examined changes throughout the course of an individual's lifetime in response to how this bone is used. Thus, this particular bone reflects how an individual used his joints and hands and what the researchers found were suggestive of hands that wielded tools.
"Australopiths were not only capable of using their hands in more human-like ways than living great apes, but also that they actually used their hands in more human-like ways. That's why the bone (in A. africanus) has remodeled in response to that more human-like hand use," said Matthew Tocheri from Lakehead University.
The result of the study encourages researchers to focus on evidence for tools that were used by our ape-like ancestors at least 3 million years ago.
