From Bruce Bawer at Science News::
A largely complete, 3.3-million-year-old child’s foot from Australopithecus afarensis shows that the appendage would have aligned the ankle and knee under the body’s center of mass, a crucial design feature for upright walking, scientists report July 4 in Science Advances.
“The overall anatomy of this child’s foot is strikingly humanlike,” says study director Jeremy DeSilva, a paleoanthropologist at Dartmouth College in Hanover.
But the foot retains some hints of apelike traits. Compared with children today, for example, the A. afarensis child — only about 3 years old at the time of death — had toes more capable of holding onto objects or anyone who was carrying her, the team found. Those toes included a somewhat apelike, grasping big toe. “Young children having some ability to grasp mom could have made a big energetic difference for Australopithecus afarensis adults as they traveled,” DeSilva says.
Even if a young A. afarensis could have fit more items between its big toe and second toe than a human child can, the ancient youngster would not have had a grasping ability even close to that of a modern-day ape, Ward says. More.
Paper. (open access)
Abstract: The functional and evolutionary implications of primitive retentions in early hominin feet have been under debate since the discovery of Australopithecus afarensis. Ontogeny can provide insight into adult phenotypes, but juvenile early hominin foot fossils are exceptionally rare. We analyze a nearly complete, 3.32-million-year-old juvenile foot of A. afarensis (DIK-1-1f). We show that juvenile A. afarensis individuals already had many of the bipedal features found in adult specimens. However, they also had medial cuneiform traits associated with increased hallucal mobility and a more gracile calcaneal tuber, which is unexpected on the basis of known adult morphologies. Selection for traits functionally associated with juvenile pedal grasping may provide a new perspective on their retention in the more terrestrial adult A. afarensis. More.
Hmmm. How good are modern toddlers at grasping things with their feet? Few cultures encourage it so we don’t know what the comparison would show if current human cultures regularly encouraged the habit. The advent of shoes likely killed whatever skill existed dead.
See also: Do racial assumptions prevent recognizing Homo erectus as fully human?
What happens when children are born without arms? Notice how hand-like, the girl’s feet became.