Researchers say some humans are developing an extra artery in their arms

Researchers from Flinders University and the University of Adelaide in Australia have discovered something interesting in some humans. When in the womb, babies have a temporary artery that runs down the center of the forearm that typically vanishes over time. However, that artery isn't disappearing as often as it used to.Scientists say that means more adults than ever have what amounts to an extra channel of vascular tissue under the wrist. The change is a significant increase from the mid-1880s when only 10 percent of people were born with the extra artery in place compared to 30 percent born with it in the late 20th century. Scientists point to this as evidence that humans are still evolving and note that the increase in such a short period is significant.

The median artery forms early in development in humans and transports blood down the center of the arms to feed the hands as they grow. It typically regresses at around eight weeks, leaving two other blood vessels known as the radial and ulnar arteries. In the research, scientists studied 80 limbs from cadavers that were donated by Australians of European descent. Donors range from 51 to 101 years old when they passed away, meaning they were born in the first half of the 20th century.

During the research, the team noted how often they found the median artery still capable of carrying an adequate blood supply and comparing that to figures from a literature search of the past. They believe it means that natural selection favors those who hold onto the extra blood supply. The increase in retention for the vessel could result from mutated genes involved in median artery development, resulting from health problems with the mother during pregnancy, or both.

Researchers say that they expect to see more retention of the vessel in the coming years. They note if the trend continues, most people have a median artery in the forearm by 2100.