Human-Like Hands Came Before Actual Humans

Human-like hands preceded actual humans, suggests a new study that presents compelling evidence that some of the earliest, and still very ape-looking members of our family tree were the first to process foods, make handcrafted stone tools, and do relatively sophisticated tasks.

The study, published in the latest issue of the journal Science, challenges the long-standing assumption that Homo habilis, a.k.a. "Handy Man," was the first crafter of stone tools.

"Instead, I think our findings show that the traditional view that stone tool use was something that only members of our own genus Homo were capable of is outdated," senior author Tracy Kivell told Discovery News, explaining that stone tool usage "goes back much earlier -- long before the appearance of Homo -- than we originally thought."

Kivell, a paleoanthropologist at the University of Kent and the Max Planck Institute for Evolutionary Anthropology, lead author Matthew Skinner, and their colleagues came to that conclusion after analyzing bones from Australopithecus hands from the Pliocene Epoch, approximately 5.3-2.6 million years ago.

Australopithecus individuals had a mixture of ape and human features. They sported foot and leg bones suited for walking upright, but had long arms appropriate for tree climbing.

The researchers found that Australopithecus africanus had human-like hands that were capable of precision grips, such as squeezing small objects. These early members of the human family tree also had an opposable thumb. The hand features likely evolved from even earlier human ancestors that possessed long fingers and short thumbs, which facilitate maneuvering in trees.

Prior studies have found that both making and utilizing stone tools by hand requires forceful, precision-pinch grips. Since A. africanus could use its hands in such a way, logic holds that they were indeed making stone tools, but where are the tools?

That is now a big mystery, because the earliest known stone tools date to after A. africanus lived.

"The first recognizable stone tools consist of stone pebbles and simple flakes and date to about 2.5 million years ago from Ethiopia," Skinner, who is a paleoanthropologist at the University of Kent and the Max Planck Institute for Evolutionary Anthropology, said. "This is also when we start to find animal bones with cut-marks made from stone tools."

"However," he added, "there is some evidence for these type of cut-marks at 3.4 million years ago, a time period only associated with australopiths."

There are challenges to finding very early stone tools, he explained, because "they are likely very simple flakes that were originally scattered across the landscape."

Matthew Tocheri, who is Canada Research Chair in Human Origins at Lakehead University, told Discovery News that the new study makes a convincing case that "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."

He suspects that the lack of stone tools in the archaeological record prior to 2.5 million years ago suggests that the tools were not as adaptively important to A. africanus as they were to later humans.

Brian Richmond, a curator in the Division of Anthropology at the American Museum of Natural History, said, "With this study, we finally have evidence of what we long suspected--australopiths used their human-like hand proportions to handle objects in human-like ways."

Richmond further said that the study raises many new questions, and not just about the missing tools. For example, he wonders if all australopiths had human-like hands, or if it was just A. africanus. Also, he is curious if the bones provide evidence for frequent, or infrequent but high-intensity, hand activity.

Read more at Discovery News