1.5 million-year-old human hand fossil showed evidence of complex tool use
Researchers have discovered a 1.5 million-year-old fossil that possesses an anatomical feature that is believed to be vital for making and using complex tools. The implication is that our human ancestors had the ability to make tools 500,000 years earlier than believed.
The discovered fossil is a third metacarpal bone, a bone in the palm which allows the hand to lock into the wrist bone. It was unearthed in northern Kenya, west of Lake Turkana. The hand-bone fossil is about 1.42 million years old and researchers suspect it belonged to the extinct human species Homo erectus, an early predecessor of modern humans.
According to the researchers, it is not just intelligence which gives a species the ability to make complex tools; it is also the anatomical features of the hands. Apes, for example, lack a powerful and precise enough grip to create and use complex tools effectively.
"There's a little projection of bone in the third metacarpal known as a "styloid process" that we need for tools," said study lead author Carol Ward, an anatomist and paleoanthropologist at the University of Missouri. "This tiny bit of bone in the palm of the hand helps the metacarpal lock into the wrist, helping the thumb and fingers apply greater amounts of pressure to the wrist and palm. It's part of a whole complex of features that allows us the dexterity and strength to make and use complex tools."
Until now, it was believed that only modern humans (Homo sapiens), Neanderthals, and a few other human ancestors possessed the styloid process, but it was not known exactly when this feature first emerged. It was believed to be fairly recent, in evolutionary terms, but now it appears that the feature is fundamental to the genus Homo, which began about 2.5 million years ago.
The researchers now want to find older hand bones "to see when this feature evolved," Ward said. "We want to get closer to 2 million years ago to find out when this transition to modern hand anatomy took place."