When thinking about evolution, we rarely think about how we, as humans, are continuously evolving. If the topic of human evolution does come up, we tend to think in terms of dramatic changes manifesting over centuries, like changes in brain structure or eye sizes. However, evolution is just a combination of small changes combining to give rise to new features over extended periods of time. 

In a research conducted by Flinders University and University of Adelaide in Australia, the occurrence of an artery in the human body was studied. This artery, commonly known as the median artery, is a common sight while humans are still in the womb, running down the centre of the forearm. At around 8 weeks it starts regressing, and shifts the responsibility of the blood it was carrying to the other two arteries in the forearm: the radial and ulnar arteries. It can take up to a few months to completely vanish too. However, its vanishing is not always guaranteed. 

The researchers conducted a research, using 78 limbs from cadavers donated by Australians of European descent, nearly all of them born in the earlier half of the 20th century. The goal of the research was to compare the general prevalence of persistent median arteries in modern day to its prevalence in earlier generations. Data for earlier generations was taken from old records and checked so that it did not accidentally overstate the numbers. The results were curious. In the 1880s nearly 10% people had a persistent median artery. The percentage had increased to about 30% in people born in the late 20th century. By 2100, more than half the population might have a persistent median artery. 

The implications of this are interesting. Naturally having increased blood supply to the arms and hands might signify a greater blood supply, boosting dexterity and strength. However, other researches indicate this could actually increase the risk of carpal tunnel syndrome, which diminishes hand usage, as well as causing discomfort. 

The increase in the artery’s prevalence has been linked to genetic mutational factors, as well as problems mothers face during pregnancy. 

The increase in the occurrence of this artery is not unlike the slow reappearance of the fabella bone in human knees, a feature which is three times more common today than it was a century ago. 

The research was published in the Journal of Anatomy.

References

https://www.sciencealert.com/more-of-us-are-growing-an-additional-artery-in-our-arm-showing-we-re-still-evolving/amp

https://bigthink.com/surprising-science/median-artery

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