Human Skull Evolved Along With Two-Legged Walking: Study

Posted: Mar 19 2017, 10:27am CDT | by , Updated: Mar 19 2017, 2:00pm CDT, in News | Latest Science News

 

Human Skull Evolved Along with Two-Legged Walking: Study
Comparison of the positioning of the foramen magnum in a bipedal springhare (left) and its closest quadrupedal relative, the scaly-tailed squirrel. Credit: Russo and Kirk, University of Texas
 

The evolution of human bipedalism is tied to distinctive hole in our skull

A new study confirms that the evolution of bipedalism in humans is driven by the changes in their skulls.

Bipedalsim or walking upright on two legs is a trait that separates the first hominids from four-legged apes. This evolution of this distinctive feature is often attributed to a hole on the bottom of human’s skull known as foramen magnum. However, not everyone agrees on the importance of foramen magnum in terms of developing bipedal habits among hominids.

In the 1920s, an anatomist Raymond Dart discovered the skull of Taung Child in South Africa. Taung Child had a small brain and many researchers thought that the three-million-year-old Taung fossil belonged to an ape and walked on four legs. But the presence of distinctive hole in the skull in which the spinal cord runs through suggested otherwise. It indicated that Taung held its head erect and therefore likely walked upright on its two feet.

Although the connection between foramen magnum and bipedalism seems logical, there’s not much strong evidence to back up this notion. The question of how bipedalism evolved could come closer to an answer if paleoanthropologists managed to find more fossils of the earliest hominids, which they actually did not. 

However, in a study published in the 2013 Journal of Human Evolution, anthropologists from university of Texas Gabrielle Russo and Christopher Kirk suggested a new way to reach a conclusion. The noted that human foramen magnum is often explained as an adaptation for maintaining balance of the head during bipedalism. This forward-shifted foramen magnum is found not just in humans and their bipedal fossil relatives, but feature has evolved independently among mammals groups other than primates. 

“This question of how bipedalism influences skull anatomy keeps coming up partly because it's difficult to test the various hypotheses if you only focus on primates," said Kirk. "However, when you look at the full range of diversity across mammals, the evidence is compelling that bipedalism and a forward-shifted foramen magnum go hand-in-hand."

In the latest study, researchers expanded on their previous research by using new methods to study foramen magnum in humans, kangaroos, springhares and jerboas and compared the results with 77 mammal species including marsupials, rodents and primates. They concluded that humans and other bipedal mammals have a more forward-positioned foramen magnum than their quadrupedal close relatives. 

“We've now shown that the foramen magnum is forward-shifted across multiple bipedal mammalian clades using multiple metrics from the skull, which I think is convincing evidence that we're capturing a real phenomenon," said Russo.

"Other researchers should feel confident in making use of our data to interpret the human fossil record.”

 

 

 

 

 

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Hira Bashir covers daily affairs around the world.

 

 

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