Over generations, more people born with an extra artery in their forearm shows modern humans are evolving at the fastest rate in the past 250 years and the natural selection could be the major reason, Australian researchers said.
The recently published study showed the number of people who retained the median artery has been increasing significantly since the 19th century and everyone will have the artery by the end of this century if the trend continues.
Co-researcher Dr. Teghan Lucas from Flinders University in Australia told Xinhua on Friday that the median artery naturally disappears during embryonic development as it is replaced with two other major arteries which supply the forearm.
However, it is not disappearing in many humans and persists into adulthood, especially for people born in the late 20th century. Lucas said the artery cause no harm to body which makes sense for natural selection to keep it in a faster human embryonic development process.
"Embryonic development is now faster to the extent that WHO changed the definition of the normal duration of pregnancy from 40 weeks to 39 weeks," Lucas said.
"Thus, evolution has decided to keep the artery and not spend the body's resources in removing it. "
As a matter of fact, the extra artery has evolutionary advantages to some people as it provides better overall blood supply and can be harvested as a replacement artery if the operation is needed on other parts of the body, according to senior author Professor Maciej Henneberg from the University of Adelaide in Australia.
"This is micro evolution 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," Henneberg said.