Fossil suggests 1.98-mn-year-old Au. sediba may be handier than Homo habilis

A 1.98-million-year-old human hand makes a better candidate for an early tool-making hominin hand than the Homo habilis hand, and may well have been a predecessor from which the later Homo hand evolved, according to a new study.

An international team of researchers has described the earliest, most complete fossil hominin hand post-dating the appearance of stone tools in the archaeological record, the hand of a 1.98-million-year-old Australopithecus sediba from Malapa, South Africa.

The researchers found that Au. sediba used its hand for arboreal locomotion but was also capable of human-like precision grips, a prerequisite for tool-making.

The fossil remains of an adult female Au. sediba include an almost complete right hand in association with the right forelimb bones, in addition to several bones from the left hand.

The researchers reconstructed the Au. sediba hand, then compared it with other hominin fossils and investigated the presence of several features that have been associated with human-like precision grip and the ability to make stone tools.

They found that Au. sediba has many of these features, including a relatively long thumb compared to the fingers – longer than even that of modern humans – that would facilitate thumb-to-finger precision grips.

Importantly, Au. sediba has more features related to tool-making than the 1.75-million-year-old “OH 7 hand” that was used to originally define the “handy man” species, Homo habilis.

“Taken together, we conclude that mosaic morphology of Au. sediba had a hand still used for arboreal locomotion but was also capable of human-like precision grips”, Tracy Kivell of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.

“In comparison with the hand of Homo habilis, Au. sediba makes a better candidate for an early tool-making hominin hand and the condition from which the later Homo hand evolved,” Kivell concluded.