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Under the Microscope
Fri January 10, 2014
MU professor leads research dating the origin of human dexterity
Our hand, the one we use to scroll down this page, is a feature that helps distinguishes us as a species. Carol Ward, professor at the MU Department of Pathology and Anatomical Sciences, puts it this way:
“What we can do with our hands, the way we manipulate objects and use tools and technology, shape all of who we are as a species and how we adapt to the world.”
And part of what makes the Homo sapiens hand so distinctive is its ability to make a particularly forceful grip when using and making tools. Modern humans and Neandertals have that grip, but Ward says researchers don’t know when it developed on the evolutionary history timeline.
“We didn’t know if it was something recent with the advent of really complex stone tools, or something ancient,” Ward said.
That is, until the West Turkana Paleo Project, a research team that’s currently looking for fossil evidence of human origins in West Turkana, Kenya, discovered an early hominin bone that had some answers.
“Immediately, I looked at it, and knew it was something significant,” Ward said.
The bone is a third metacarpal, which is the fancy name for the bone that connects the middle finger to the wrist. Ward knew it was special because even though the bone obviously belonged to an early hominin, it has what’s called the styloid process: a little projection on the end of the bone that helps lock it to the wrist bones. The process helps hands make that forceful grip.
Before the discovery, “The styloid process is only found in modern humans, in Neandertals, in members of our own species,” Ward said. “So maybe 500,000-600,000, maybe even 800,000 years ago, we knew we had this anatomy and we knew they were making complex stone tools.”
The hand bone’s discovery dates the styloid process, and in turn, the origin of modern human dexterity, 600,000 years earlier than researchers thought.
“It fills in a gap in our understanding of how humans evolved,” Ward said. “We have not known when that hand appeared in our evolution. … And it turns out it comes all the way back to the origins of our genus Homo, so it’s really fundamental to who we are and may have pre-adapted us to develop all the kinds of technology that we use today.”
Ward, who co-leads the West Turkana Paleo Project with a Kenyan paleontologist, says she’s excited to make more trips to the research site where they found the metacarpal bone.
“It’s a very, very rich area,” Ward said. “Some of the most significant fossils in all of human evolution have come from West Turkana.”
Ward jokes that the research on the ancient third metacarpal bone is her second installment of publishing the story of human evolution one bone at a time. In 2011, a research she led discovered that Lucy, an Australopithecus afarensis, had arches on her foot like modern humans.
“We’ve just been lucky that even isolated bones can tell us really important things about human evolutions, which is pretty amazing and kind of fun,” Ward said.