Fossil is earliest evidence of human hand evolution for tool use

FAYETTEVILLE, Ark., Dec. 17 (UPI) -- A hand bone from an early human ancestor found in East Africa shows the earliest evidence of a structural feature related to tool use, anthropologists say.

Dated to 1.42 million years old, the bone from the early hominin Australopithecus anamensis suggests a distinctive feature of modern hands evolved more than a half million years earlier than previously thought, scientists at the University of Arkansas, Fayetteville, said Monday.

"Modern human hands are specialized to hold tools, but hand bones are difficult to find, and we haven't known when modern human hands developed," anthropology Professor J. Michael Plavcan said. "With this discovery, we have the earliest evidence of the structural changes of the hand that are associated with tool use."

The third metacarpal bone, discovered in Kenya, displayed a styloid process, a curved projection at the end of the bone important to a hand that uses tools with both dexterity and precision, the researcher said.

While stone tools date back at least 2.58 million years, until this discovery the earliest evidence of structural characteristics related to tool use dated back just 800,000 years, they said.

"There's still a huge gap in our understanding of the evolution of the hand," Plavcan said. "We need to find even earlier bones to determine just when structural features of the hand appeared."