Human Skull Evolved Along with Two-Legged Walking, Study Confirms

However, in a study published in the Journal of Human Evolution, UT Austin anthropology alumna Gabrielle Russo, now an assistant professor at Stony Brook University, and UT Austin anthropologist Chris Kirk built on their own prior research to show that a forward-shifted foramen magnum is found not just in humans and their bipedal fossil relatives, but is a shared feature of bipedal mammals more generally.

“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,” Kirk said. “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 this study, Russo and Kirk expanded on their previous research (published in the same journal in 2013) by using new methods to quantify aspects of foramen magnum anatomy and sampling the largest number of mammal species to date.

To make their case, Russo and Kirk compared the position and orientation of the foramen magnum in 77 mammal species including marsupials, rodents and primates. Their findings indicate that bipedal mammals such as humans, kangaroos, springhares and jerboas 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,” Russo said.

Additionally, the study identifies specific measurements that can be applied to future research to map out the evolution of bipedalism. “Other researchers should feel confident in making use of our data to interpret the human fossil record,” Russo said.