The skeleton of Lucy, the famous fossil remains of an early human ancestor, turn out to be not quite as complete as always believed, say researchers who've said they think they've identified one of Lucy's bones as actually belonging to an ancient baboon.
Lucy was pieced together from dozens of fossilized fragments discovered in 1972 in Ethiopia, all belonging to one hominin skeleton dated as around 3.2 million years old.
The skeleton of an Australopithecus afarensis was dubbed Lucy after a Beatles song playing on the discovers' cassette player while they celebrated their finding.
Lucy has long been considered a significant specimen of one of our earliest ancestors, in part because of the completeness of the skeleton, of which replicas have been made for museums around the world.
However, the original is apparently a little less complete than previously believed, report researchers at the American Museum of Natural History in New York, who recently started creating a new reconstruction of the fossil skeleton.
Museum scientists Gary Sawyer and Mike Smith, joined by Scott Williams of New York University, noticed something strange about Lucy — or at least one part of her.
"Mike pointed out that one of the [vertebra] fragments, which no one, including me, had really paid close attention to, looked fairly small to fit with the rest of Lucy's vertebral column," says Williams.
The scientists first thought was that the fragment had come from another younger member of the species; around 300 individuals of the species have been discovered to date.
However, comparison studies with other Australopithecus fossils from the region in Ethiopia rules out that possibility, they said.
Further study strongly suggested it didn't come from an Australopithecus, and in fact likely didn't belong to any kind of early human at all.
"It was just too small," says Williams.
So what is it? The researchers, after considerable study, decided a baboon bone was the closest fit to the mystery bone among Lucy's remains.
"Baboons were a close match, both in shape and size," Williams states. "So we think we've solved this mystery. It seems that a fossil gelada baboon thoracic vertebra washed [into] or was otherwise transported in the mix of Lucy's remains."
However, he stresses, their close study of Lucy confirms that all the other bones — 88 in all — have been correctly identified as that of an Australopithecus hominim.