Reseacher Analyzes Oldest Fossil Hominin Ear Bones Ever Recovered

In a recent finding, an anthropologist from Binghamton University has analyzed the tiny ear bones, the malleus, incus and stapes from two different species of early human ancestors from South Africa. This new study sheds light on the earliest known existence of humans.

The study, published by the National Academy of Sciences, was conducted by anthropologist Rolf Quam from Binghamton University in collaboration with researchers from Spain, the U.S. and Italy.

One of the smallest bones in the human body are the ossicles, and are rarely found in the human fossils recovered. Unlike the other bones of the skeleton, the ossicles are completely formed and adult-sized at birth. This shows that both the size and shape of the ossicles are under high genetic control. Despite being the smallest bones, they carry loads of evolutionary information.

In the new study, the researchers analyzed several auditory ossicles of the early hominin species Paranthropus robustus and Australopithecus africanus. The study consisted of all the three ear bones i.e., the oldest complete ossicular chain of a fossil hominin. They were excavated from South African cave sites of Swartkrans and Sterkfontein, dating back to two million years ago.

The researchers noticed that the malleus is human-like, and its size and shape can be distinguished from close relatives like gorillas and chimps. The skull, teeth and skeleton are ape-like, but the malleus is similar to our own specie i.e., Homo sapiens. Looking at this, the researchers claim that since a human-like malleus is seen in the hominin, it is clear that the changes in the bone occurred early in evolutionary history.

"Bipedalism (walking on two feet) and a reduction in the size of the canine teeth have long been held up as the "hallmark of humanity" since they seem to be present in the earliest human fossils recovered to date. Our study suggests that the list may need to be updated to include changes in the malleus as well. More fossils from even earlier time periods are needed to corroborate this assertion," Quam said in a press statement.

Unlike the malleus, the incus and stapes were more like chimps, orangutans and gorillas. To their surprise, the ossicles were a combination of ape-like and human-like features.

Further, the team plans on studying the functional features of the ear in early hominins with the help of 3-D virtual reconstructions based on high-resolution CT scans.