Former human ancestors had to deal with climbing toddlers

More than three million years ago, our adult human ancestors walked on two feet and did not have the option of a fashionable scarf for carry their children. Instead, Australopithecus afarensis toddlers had a special gripping toe that helped them hang on to their mothers and escape into the trees, reports a study published today (July 4th) in Science Advances.

The evidence comes from DIK-1-1 – a relatively complete skeleton 3.3 million years old of a female aged 2.5 to 3 years Australopithecus afarensis discovered in Dikika, Ethiopia. The skeleton, nicknamed Selam – after the word for peace in the official language of Amharic in Ethiopia – includes the oldest and most complete leg bones ever found. [Image Gallery: 3-Year-Old Human Ancestor ‘Selam’ Revealed]

"It's a very exciting discovery," said Will Harcourt-Smith, paleontologist at the American Museum of Natural History in New York, who did not participate in the event. 39; study and was a critic of the newspaper. "It's really special and really allows us to learn something more about this creature."

Human-like, with a chimp-like toe

Zeresenay Alemseged, a paleoanthropologist from the University of Chicago, discovered the preserved skeleton of Selam in 2000 The skeleton was originally dubbed "Lucy's baby." "because of its proximity to the adult female A. afarensis fossil named Lucy, found in 1974. But Selam died more than 100,000 years before Lucy was still alive.

Selam's foot was discovered in 2002 and is about 5 inches long – it's a little shorter than a sticky note. The structure of the ankle and the general anatomy of the foot are the same as those of a modern human, with a distinct difference: the big toe is curved, similar to that of a chimpanzee. But unlike the big toe of the chimpanzee, Selam is in line with his other toes, similar to the toes of a human foot.

"So it's human not to stick to it but it had a lot more mobility and could probably shake and hang on to things, not a chimp, but certainly more than a human, "said Jeremy DeSilva, paleoanthropologist at Dartmouth College in New Hamphshire and senior author.

The anatomy of Selam's heel was also surprising, a He said … Lucy and another adult afarensis fossils had sturdy heel bones that are similar to those that humans were born with, and they are adapted to walk upright.But the heel of Selam was relatively small and delicate. "This suggests that [ A. Afarensis ] grew up very differently from us," DeSilva told Live Science. "Even though we have the same anatomy, they still 39 had different. "

Climbing, but walking over

L & # 39; Selam's curved toe suggests that A. afarensis infants and toddlers grabbed their mother's body while being transported and also climbed on trees for food or protection, especially at night. This is an inference based on the fact that there is no evidence of fire or construction for another million years in Africa, DeSilva said. "We also have fossils of very large predators," he said. "I can not imagine how they would have survived if they did not go to the trees at night."

But they were still not great climbers, says Carol Ward, an anatomist and paleoanthropologist at the University of Missouri who did not participate in this study, but who analyzes S's Colum e vertebral and ribs of Elam. "Even if a baby could have adapted to more things between his first and second toe, he would not have had the ability to seize like a monkey," Ward said in Live Science in an e -mail. She said that Selam's foot is clearly suited to walk on two feet and shows "how important life on earth was for these animals, and that effective climbing was less important."

Although Selam's foot is relatively complete, it could miss pieces of cartilage that have rotten over time. "It makes it a bit difficult to say everything you could want about how the joints work," Harcourt-Smith told Live Science. For example, the researchers "argue that the bow is low and maybe flat in this individual, and I think they're probably right, but you have to take it with a little salt," he said.

The discovery is unprecedented and "allows us to study the growth and development of our ancestors in a way that we do not have," DeSilva said. "He opens this window on what was the life of a child 3 million years ago."

Original article on Live Science.