Ever since the first discovery of Neandertal remains nearly 150 years ago, researchers have debated the biological and behavioral similarities and differences between those archaic humans and anatomically modern Homo sapiens. In recent years a number of discoveries have revealed similarities between the two groups. Indeed, archaeological remnants from Neandertal and early modern sites in the Near East, where the groups coexisted for thousands of years, are almost indistinguishable. Findings reported today in the Proceedings of the National Academy of Sciences Early Edition, however, point to differences in hand anatomy that may have enabled early modern humans to make a key shift in manipulative behaviorone that contributed significantly to the group's evolutionary success.

Wesley A. Niewoehner of the University of New Mexico studied hand remains from Near Eastern Neandertals and early moderns dating back to roughly 100,000 years ago, as well as remains from later moderns. He found that the Neandertal handwith its broad fingertips, pronounced crests for muscle attachments and greater thumb leverage, among other thingswas well suited to forceful "transverse power grips," such as those used in gripping a hammerstone. The early modern hand, in contrast, exhibits features on the base of the thumb, index and middle fingers that made it well adapted to "oblique power gripping"gripping a hammer handle, for example. Living humans, too, often employ oblique power gripping when wielding a hafted tool. And although hafted tools are known from Neandertal sites, some archaeological evidence suggests that they figured more importantly in the early modern toolkit.

"A hand better suited to oblique power grips as found by Niewoehner, and by a greater use of hafting, are not in themselves adaptive innovations sufficient to have given modern humans a competitive edge over indigenous archaic populations," Duke University paleoanthropologist Steven Churchill writes in a commentary accompanying the PNAS report. "Rather, these differences are likely part of an emerging modern human adaptive system that involved a greater use of task-specific tools, more complex composite tools, greater planning depth and logistical complexity to foraging, and increased social complexity."