This seems rather dubious to me; what selection pressure exists that's increasing fitness for people with three arteries?
The fact that it's progressing so rapidly suggests that this is either bad data, or environmental changes
According to the abstract, there has been a significant (p-value of under 0.001) increase in the prevalence of mid-arm arteries over time, which has been corroborated by multiple studies.
After removing studies that focus specifically on the evolutionary aspect of this change, the p-value is 0.018, which still suggests a correlation.
Why does increased blood supply create such a large selection pressure? And what type of surgical procedure uses the median artery as a replacement part?
I have zero training in biology, so I think my mental model must be very off.
- selection pressure for some other trait that happens to involve some genetic material that affects the forearm arteries.
- the recent removal of strong selection pressure for having two arteries, on a trait that generally tends to drift towards three arteries in many directions.
- a dominant gene isolated to one province, which then got diluted across the population when people traveled more.
- a trait found more often in the rural population, which over the past century had more children.
>It runs with the median nerve and supplies the same structures as that nerve.
so, may be it affects dexterity (or ability to sustain it). That would be a huge boon in our industrial and post industrial society. May be it decreases load on the other 2 arteries and thus again improves some aspects of blood flow supply in the arms and/or to the palms. Also the dexterity seems to be a major factor in early brain development, kind of feedback loop. It may also just correlate with/manifest some overall characteristic (say "branch-ness") of the blood vessel system which say provides better blood flow to the body and/or brain.
It also may be just a characteristic prevalent in some ethnicity or region, and the last 1-2 centuries there has been a lot of people moving/mixing, and if it is a dominant allele then it would explain such a fast spread.
> Senior author Professor Maciej Henneberg who is also a member of the Institute of Evolutionary Medicine at the University of Zurich, Switzerland, says the median artery offers benefits because it increases overall blood supply and can be used as a replacement in surgical procedures in other parts of the human body.
But that's what I want explained why is more blood beneficial for a person's forearm?
I don't feel like I am lacking blood flow during my daily tasks in life. Can "extra arm artery mutant guy" out-compete me in a specific task so critical it means his genes are more likely survive than mine are?
Worse, Wikipedia claims it’s easier to commit suicide by slashing your wrists if you have this artery (https://en.wikipedia.org/wiki/Median_artery), and https://radiopaedia.org/articles/persistent-median-artery-of... says it can be a cause of carpal tunnel syndrome.
I don’t see how either could be an evolutionary advantage.
The most likely answer is that natural selection isn't directly driving this specific trait.
Perhaps those that developed differently to have this artery retained were selected against in less civilised times.