The styloid process has been found on all true human fossils for which the metacarpals have been found-including Neanderthals and Homo heidelbergensis. It’s part of a whole complex of features that allows us the dexterity and strength to make and use complex tools.” “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. “There’s a little projection of bone in the third metacarpal known as a ‘styloid process’ that we need for tools,” explains paleoanthropologist Carol Ward, lead author of the study published in the Proceedings of the National Academy of Sciences. The dexterity made possible by unique features like the styloid process facilitates the human ability to make tools, whether flaked stone axes or optical equipment. The styloid process distributes the stresses created as the thumb pinches and squeezes from a myriad of positions so as to minimize shearing and tearing. Why is the styloid process so important? Without the styloid process to lock the metacarpal into the wrist bones, the entire wrist-a complex of hand, thumb, forearm, and wrist bones formed to fit together perfectly-lacks the stability needed to manipulate objects with both strength and precision.
CHIMPANZEE HAND FOSSIL MANUAL
A little bony projection on the wrist-end of this metacarpal-the styloid process-is unique to humans and essential for the manual precision that is a human trademark. The third metacarpal is the long bone underlying the palm and connecting the middle finger to the wrist bones. The bone, found in East African Lower Pleistocene rock conventionally dated at 1.42 million years, is a third metacarpal. They assert that a hand “preadapted” for precision and manual dexterity may have helped humans produce complex tools and pull themselves up the evolutionary ladder.
Finding this unmistakably human bone unexpectedly deep in the fossil record has prompted them to suppose that ape-like hand bones rearranged themselves to human form half a million years earlier than previously thought. The discovery of a hand bone in Kenyan rock has evolutionary anthropologists pushing back the timeline for evolution of the human hand. Discover: “ Discovery of Partial Skeleton Suggest Ruggedly Built, Tree-Climbing Human Ancestor”.
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