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rhamphotheca:

“Lucy’s Baby” a Born Climber, Hinting Human Ancestors Lingered in Trees

Australopithecus afarensis’ shoulders pointed upward, new fossil study suggests.

by James Owen

What made us human? Part of the answer may rest on the shoulders of a 3.3-million-year-old toddler.

Like “Lucy,” the fossil child was a member of the speciesAustralopithecus afarensis, pioneers of upright walking. Yet her apelike shoulder blades hint that our forebears may have taken longer than we thought to fully come down to earth, a new study says.

Figuring out when the tree-to-ground transition took place is immensely important to understanding how we became who we are. Bipedalism, after all, gave prehumans a literal head’s-up on approaching predators and freed up hands for stone tools, which in turn gave access to more types of food, including brain-boosting animal proteins—among other advantages.

The tiny fossils—including the only known complete A. afarensis scapula, or shoulder blade—add to evidence that that giant stride was more a series of faltering steps.

“What we’re showing is that bipedalism wasn’t this sudden change that took shape in an early common ancestor,” said study co-author David Green, an anatomy professor at Midwestern University in Downers Grove, Illinois. “As bipedalism was developing, there were other forms of locomotion that were still important.”

(read more: National Geo)

(images: T - Dave Einsel/Getty; B - Zeray Alemseged / Dikika Research Project)