Published: Sun, July 08, 2018
Science | By Michele Flores

Study shows ancient ancestors climbed trees, also walked on two legs

Study shows ancient ancestors climbed trees, also walked on two legs

"Not [as well as] a chimp, but certainly more than a human could", said Jeremy DeSilva, a paleoanthropologist at Dartmouth College in New Hamphshire and lead author of the study.

"Studying younger individuals is important because the morphology that you see in adults is the result of both their evolution through time and how they changed as they grew", Alemseged, senior author of the study, wrote in an email.

Astonishingly, it is part of an nearly complete skeleton of a young female Australopithecus afarensis living 3.32 million years ago in the Dikika region of Ethiopia.

Back in 2002, archaeologists discovered a almost complete human skeleton, which turned out to be remains of a female toddler who lived in East Africa three and half million years ago but died before reaching the age of four.

"Placed at a critical time and the cusp of being human, Australopithecus afarensis was more derived than Ardipithecus (a facultative biped) but not yet an obligate strider like Homo erectus".

The Dikika foot is one part of a partial skeleton of a 3.32 million-year-old skeleton of an Australopithecus afarensis child. Later, Selam was found just a few miles away from Lucy and was then given the nickname "baby Lucy", despite being alive around 200,000 years before Lucy.

According to CNN, Selam was similar in size to a chimpanzee and depended on her mother for survival.

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Selam's curved toe suggests that A. afarensis infants and toddlers were grasping their mother's body while being carried and were also climbing trees for food or protection, especially at night.

"If you were living in Africa three million years ago without fire, without structures, and without any means of defence, you'd better be able get up in a tree when the sun goes down", said Dr DeSilva. Even with those abilities, she would have been better at walking than climbing.

The toe most modern humans refer lovingly to as the "big toe" here looks ever-so-slightly different in Selam.

The anatomy of Selam's foot was incredibly well-preserved, allowing the researchers to study how a toddler hominin would have walked. But fossilized hints-namely the base of the big toe-hint that children spent more time in trees than adults. Lucy and other adult A. afarensis fossils had robust heel bones that are similar to those that humans are born with, and they're suitable for walking upright.

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. She said Selam's foot is clearly adapted for walking on two feet and shows "how important life on the ground was for these animals, and that effective climbing was much less important".

These findings could shed light on the evolution of walking upright and shows how crucial the afarensis species was for human evolution.

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