If you thought that humans had stopped evolving, think again. Researchers in Australia have just published a study proving that humans are continuing to change. While evolution can be so slow that it is hard to see concrete examples within a single lifetime, the recent appearance of an extra artery in our arms highlights our constant development.
The median artery develops in all humans while in the womb, helping bring the extra blood needed to develop our growing hands. Typically, this blood vessel deteriorates after about eight weeks, leaving the two other main arteries—radial and ulnar—to continue on. However, occasionally this regression doesn't occur and the median artery can stick around for another few months or, sometimes, after birth.
The researchers wanted to look into the prevalence of this third artery sticking around upon birth and so they studied the cadavers of 80 Australians of European descent. What they found was remarkable. With donors ranging in age from 50 to 100 years old, the study demonstrated a startling increase in adults with this third artery.
“Since the 18th century, anatomists have been studying the prevalence of this artery in adults and our study shows it’s clearly increasing,” stated Dr. Teghan Lucas of Flinders University. “The prevalence was around 10% in people born in the mid-1880s compared to 30% in those born in the late 20th century, so that’s a significant increase in a fairly short period of time, when it comes to evolution.”
According to Dr. Lucas, this increase in adult median arteries could spring from a genetic mutation or health problems in mothers during pregnancy. Either way, if the trend continues, there will be more adult with than without median arteries by 2100.
While the presence of the median artery can be a risk factor for carpal tunnel syndrome, senior author of the study Professor Maciej Henneberg sees other benefits. Not only can the additional artery increase blood supply, but it can also be used as a replacement in surgical procedures in other parts of the body.
“This is microevolution in modern humans and the median artery is a perfect example of how we’re still evolving because people born more recently have a higher prevalence of this artery when compared to humans from previous generations,” he shares.
Of course, this isn't the only evolutionary change in humans to be recognized more recently. Other examples include the increasing absence of wisdom teeth and the resurgence of the fabella, a small bone in the back of the knee joint. Much like the median artery, this bone is now three times more common in humans than it was a hundred years ago.