If you're interested in the study or its methodology, you can request the paper directly from the authors at: https://www.researchgate.net/publication/344230933_Recently_...

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.

No need to request: https://scihubtw.tw/10.1111/joa.13224

I also find this shocking - 10% -> 30% seems like a massive change in ~100 years in the context of human evolution.

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.

Let's assume the research is sound. (Inferring from mci's comment, probably not.) But let's suppose we saw this phenomenon in a specific country's population, measured without any sampling bias. It could be from:

- 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.

There doesn't need to be selection pressure for a mutation to spread, it just needs to be no disadvantage to develop it

With no selection pressure a gene will not from 10% to 30% in a few generations. That requires a tremendous selective advantage.

Well, or it just needs to be a dominant gene.

The gene didn't become dominant in the last several generations.

That makes absolutely no difference.

from wikipedia:

>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.

Right from the article:

> 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.

>because it increases overall blood supply

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?

I would guess extra blood flow could somewhat prevent people from suffering of cold fingers. I couldn’t find evidence for that, though.

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.

More stamina when composing romantic emails → greater chance of reproduction.

Replacement makes sense, your friend with extra artery will survive in case of a critical surgery and might have another kid while you'd die with no extra kid. Does not need to happen to you but on average. Your friend with better bloodflow might also have a stronger erection and therefore on average more kids (pulling this out of my ass obviously). You dont need to have any obvious disadvantages, on average it might still work better..

If we're talking about a trend strong enough that most humans will have this trait in 80 years, then if natural selection is driving it, none of those advantages are great enough to explain that.

The most likely answer is that natural selection isn't directly driving this specific trait.

That’s not exactly a selection pressure. It would seem likely that there is no selection pressure here but in fact greater genetic diversity due to overall better survival of more and more people.

Perhaps those that developed differently to have this artery retained were selected against in less civilised times.

But that does not increase, in any way significantly, a person's reproductive success.

That second part seems unlikely to me. I would guess the percentage of people that’s beneficial to is extremely low.

So this means evolution actually reacted on progress on medicine and we are evolving our own spare parts for surgical procedures. While this makes sense im still amazed!