Wednesday, November 7, 2012

Arboreal and Bipdeal Ancestors

Australopithecus afarensis, a hominid and closely related human ancestor, was an upright-walking species, or bipedal. However, it has long been debated whether or not this species were also climbers who spent much of their time in trees. This has question has remained a mystery due to the fact that a complete set of A. afarensis shoulder blades had never been available to study. However, for the first time ever, David Green and Zeresenay Alemseged were able to analyze a complete set of shoulder blades and conduct a study on their ability to climb.

The two scientists took 11 years to extract the shoulder blades from a skeleton embedded in sandstone. The skeleton, named Selam, lived 3.3 million years ago. The extraction took so long because shoulder blades are extremely thin and rarely fossilize. When they do fossilize, they often fragment.

The scientists digitized the shoulder blades and compared them to fossils of other human relatives as well as other old world apes. They discovered that these shoulder blades were quite apelike, suggesting that this species was adapted to climbing in trees, in addition to its bipedalism.

This study is significant because it moves us closer to answering the question: When did our ancestors stop climbing? This study shows that this happened much later than previously thought. In addition, this study answers this question of arboreal adaptation that had been debated about for several decades.


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