Hominins walked like modern humans, climbed like apes: Study

New York: Our early hominin ancestors, including their toddlers, could stand on two feet and walk upright, but also had several ape-like foot characteristics that could have aided in climbing trees, a study has found.

The team discovered that hominin toddlers possessed many of the structures necessary to walk on two legs that have been found in adult specimens, but also retained a convexity of the medial cuneiform — a bone important for joint movement, such as that involved in climbing — into adulthood.

The findings, published in the journal Science Advances, are based on a rare tiny foot fossil, about the size of a human thumb, of a nearly 3.32 million-year-old skeleton of a young female hominin ancestor, Australopithecus afarensis, discovered in 2002 in the Dikika region of Ethiopia.

“For the first time, we have an amazing window into what walking was like for a two-and-a-half-year-old, more than 3 million years ago,” said lead author Jeremy DeSilva, Associate Professor at Dartmouth College in New Hampshire.

“This is the most complete foot of an ancient juvenile ever discovered.” DeSilva added.

At two-and-a-half-years-old, the Dikika child was already walking on two legs, but based on the skeletal structure of the child’s foot, specifically the base of the big toe, show that the kid probably spent more time in the trees than adults.

This evidence of increased mobility of the toe is an ape-like pattern that is suggestive of a selective advantage of this trait and which offers new insights into the evolution of bipedality, the researchers said.

“Walking on two legs is a hallmark of being human. But, walking poorly in a landscape full of predators is a recipe for extinction,” DeSilva explained.

“These findings are critical for understanding the dietary and ecological adaptation of these species and are consistent with our previous research on other parts of the skeleton especially, the shoulder blade,” said Zeresenay Alemseged, Professor at the University of Chicago in the US.