Inner ear helps scientists trace human migrations out of Africa

April 3 (UPI) — New research suggests inner ear morphology can trace the dispersion of early humans out of Africa and across the globe.

Using computed tomography, researchers collected high-resolution 3D models of the bony labyrinth, the inner ear structure, from populations all over the world. Analysis revealed a greater degree of labyrinth shape variety within populations than between populations.

“This typically human variation pattern is also known from comparative genetic data,” Marcia Ponce de León, an anthropologist at the University of Zurich, said in a news release. “It shows that all humans are very closely related and have their roots in Africa.”

Researchers also found that the further away a population was from South Africa, the more likely the population’s bony labyrinth was to differ from a South African bony labyrinth. The pattern mirrors the relationship discovered between genetic and geographical differences identified by previous genomic surveys.

The new study, published this week in the journal PNAS, also showed the inner ear shapes of prehistoric populations from Indonesia’s Sunda Islands share the most similarities with those of indigenous people of Papua and Australia. Meanwhile, the bony labyrinth of modern Sunda inhabitants is most similar to the inner ear of people from the Malay archipelago.

European and Japanese populations boast inner ear structures most similar to those of the people living in Europe and Japan during the Neolithic Period.

Despite the important role the bony labyrinth plays in assisting balance and hearing, human evolution has allowed for a surprisingly large amount of variety inside the ear.

“This is probably due to random changes in the genetic material,” said Christoph Zollikofer, professor of anthropology at UZH. “Such changes may have few or no functional consequences, but the associated structural changes provide a record of human dispersal and evolution history.”

Because the bone surrounding the bony labyrinth has a high concentration of well-protected DNA, paleontologists often mine it for genetic samples. Unfortunately, this process can damage the inner ear structure.

“Paleogenetics is a rapidly growing research field and hundreds of labyrinths from archaeological skeleton collections have already been milled to dust without first being documented,” said Zollikofer.

Moving forward, researchers hope scientists will collect computed tomographic data related to shape of the bony labyrinth before sampling DNA from human remains.

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