An oddity in your forearm proves humans aren’t done evolving yet


Just when you thought we had this whole being-a-human thing figured out, we’re apparently still changing in irreversible ways. In a new paper, scientists have identified a feature they say is actively evolving in the human forearm.

Everything in nature is always in some state of evolution, but it’s very hard to see in realtime because of how long the time scales are outside of isolated examples like the birds of the Galapagos Islands or scientific studies of fruit flies. In the new research, experts identify different kinds of human forearms: some people have something called the median artery, and some people don’t … yet.

The scientists, based in different schools in Australia, studied human remains for the presence of the median artery. “A total of 26 median arteries were found in 78 upper limbs obtained from Australians aged 51 to 101 years, who died in the period 2015–2016, a prevalence rate of 33.3 [percent],” they explain in the paper:

“Second-order polynomial regression of the median artery’s prevalence on dates of birth shows that it is now present in 35 [percent] of people and predicts that people born 80 years from now will all carry a median artery if the trend continues. When the median artery prevalence reaches 50 percent or more, it should not be considered as a variant, but as a ‘normal’ human structure.”

This content is imported from {embed-name}. You may be able to find the same content in another format, or you may be able to find more information, at their web site.

There are other qualities that are divided in this way, which scientists speculate have to do with ongoing evolution especially of human groups that came from geographically separated groups—think varying lactose tolerance, an interesting selective allergic reaction to alcohol, and other very minor characteristics.

But for a physical structure in the body to be different is much more uncommon, and even physiognomist favorites like “the bump at the base of the skull” don’t follow the population guidelines they insist are true.

This content is imported from YouTube. You may be able to find the same content in another format, or you may be able to find more information, at their web site.

The median artery forms in quite young fetuses in the womb, and as with lactose tolerance, it eventually disappears in most people. This is the key fact that scientists say is changing. They describe the median artery in adults as the persistent median artery referring to the survival past fetal development.

Persistent median arteries come in two flavors so far, named for how far they radiate down into the forearm and sometimes the hand. “Two main phenotypes of persistent median artery, almar and forearm have been described. They supply the forearm and the hand, or the forearm only, respectively,” the researchers explain. “This pattern of median artery arrangement has been referred to as the antebrachial phenotype.”

For now, the study was of just Australians of European descent, and the scientists say in the paper that they don’t yet understand the scope of how this feature has evolved around the world. They used volunteer-donated remains and only checked for the presence of a median artery, not a particularly palmar or forearm median artery.

This study is just one small step toward a much larger study of this feature in different population groups, born in different time periods and all around the world., 12 October 2020