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Did Our Early Ancestors Climb As Well As Walk?

australopithecus_1

One of the joys of scientific progress is the mysteries created by newly discovered information, and one of its banes is often in having that new mystery last longer and present more complicated issues than anything coming before it. Perhaps this is the reason for a lack of science-themed spas and other locations of relaxation.

The point at which our hominid ancestors left the trees behind for bipedal walking has been a source of debate among scholars for some time. The hominid Lucy, the 3.5-million-year-old earliest skeletal evidence of Australopithecus afarensis, was a walker, scientists agree, but a Dartmouth college study published in the journal Proceedings of the National Academy of Sciences (PNAS) may finally prove the dual nature of the species at that time.

Though the rigid ankle and arched, nongrasping foot seem to imply a lack of climbing in our evolved past, associate professor of anthropology Nathaniel Dominy and his colleagues performed field studies in the Philippines and Africa, focusing on comparisons of area tribes who rely on terrestrial tactics rarely utilized by city folk. The Twa hunger-gatherers in Uganda were compared to the Bakiga, and Philippine tribe the Agta were matched against the Manobo agriculturalists.

Both the Twa and Agta tribes have a high dependence on honey in their diet, honey they have to acquire from treetops. By using extreme dorsiflexion — bending the foot upwards at an extreme angle — not often used by those in more industrialized nations, the tribe members climb smaller-diameter tree trunks by pressing their soles to the tree and alternating their arm and leg climbing. The researchers hypothesized “that a soft-tissue mechanism might enable” this tactic, and they then used ultrasound imaging to measure the large gastrocnemius muscle fibers in the calf. Of the four groups tested, those muscle fibers in the Twa and Agta were significantly longer, suggesting that years of climbing by these tribes have altered their muscle structures.

The research team says, “This demonstrates that the development of foot and ankle adaptations for walking on land does not necessarily mean that Lucy and her kin weren’t still able to use their feet for climbing as well.” So even though we don’t have any fuzzy and questionable photographs to argue over, this modern take on an old problem has given us actual facts to discuss. And if this evidence isn’t good enough for you…well, you know what you can do.

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