No offense, Lucy, but at three feet, six inches you were kind of short. Your diminutive, 3.2 million-year-old bones made it difficult to tell whether your species could even walk like us. Fortunately, researchers in Ethiopia have uncovered an older, bigger relative. As described in Proceedings of the National Academy of Sciences, some researchers believe that these new bones show that members of Lucy’s species, Australopithecus afarensis, could walk like modern humans.
The paper’s authors call him Kadanuumuu (kah-dah-nuu-muu)–”big man” in the Afar language. Big Man still isn’t really that big by today’s standard: His 3.6 million-year-old bones show that he stood at around five feet.
The fossilized remains don’t include a head, but Big Man has many of the same bones as Lucy, and also others previously missing: a shoulder blade and a rib cage bits. Lead researcher Yohannes Haile-Selassie argues that Big Man’s skeleton upends previous beliefs about Lucy’s love of tree climbing and more primitive walk.
“This individual was fully bipedal and had the ability to walk almost like modern humans,” said Haile-Selassie. “As a result of this discovery, we can now confidently say that ‘Lucy’ and her relatives were almost as proficient walking on two legs as we are, and that the elongation of our legs came earlier in our evolution that previously thought.” [Cleveland Museum of Natural History]
Haile-Selassie argues that Lucy’s stubby legs mislead researchers into thinking that she wasn’t fully adapted to upright walking. He says that if she had been as tall as Big Man, she would have a similar stance.
Others researchers argue that the skeleton adds little new information.
Fossil hominid skeletons as complete as Big Man “are few and far between,” says anthropologist William Jungers of Stony Brook University in New York. But the new find mostly confirms what was already known about Lucy, he asserts. Lucy’s kind, including Big Man, were decent tree climbers, even if they couldn’t hang from branches or swing from limb to limb as chimpanzees do, he says. “Riddle me this,” asks Jungers in considering Hailie-Selassie’s [sic] emphasis on a ground-dwelling A. afarensis. “Where did they sleep? Did they wait for fruit to fall to the ground? Where did they go to escape predators?” [Discovery News]
Even if Big Man can’t settle the walking debate, he does give researchers some new clues about past hominids and even some close living relatives.
Carol Ward of the University of Missouri at Columbia agrees that the debate over exactly how A. afarensis walked is likely to continue. Still, Big Man does add important information about the evolution of the upper body of hominids, she notes. The shoulder blade, or scapula, is the oldest hominid scapula discovered, and an adult one, which allows for a proper comparison to other species. [Nature News]
This shoulder blade is very different from that of chimpanzees, our closest living relative, as described in a Cleveland Museum of Natural History release, meaning that chimpanzees have evolved quite a bit since we shared a last common ancestor.
Beautiful bone footage available, here.
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Image: Yohannes Haile-Selassie, Liz Russell, Cleveland Museum of Natural History.