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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 rapi

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

ceejayoz 6y ago
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.
- dghughes 6y ago
  >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?
  - fleischhauf 6y ago
    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..
    - learc83 6y ago
      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.
    - deleted 6y ago
      [deleted]
    - deleted 6y ago
      [deleted]
  - Someone 6y ago
    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 https://en.wikipedia.org/wiki/Median_artery), and https://radiopaedia.org/articles/persistent-median-artery-of-the-forearm 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.
    - leephillips 6y ago
      More stamina when composing romantic emails → greater chance of reproduction.
- fleischhauf 6y ago
  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!
- Gupie 6y ago
  But that does not increase, in any way significantly, a person's reproductive success.
- Someone 6y ago
  That second part seems unlikely to me. I would guess the percentage of people that’s beneficial to is extremely low.
- knolan 6y ago
  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.
tronbabylove 6y ago
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.
fs_tab 6y ago
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_increased_prevalence_of_the_human_median_artery_of_the_forearm_A_microevolutionary_change 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.
- oh_sigh 6y ago
  No need to request: https://scihubtw.tw/10.1111/joa.13224 https://scihubtw.tw/10.1111/joa.13224
heeen2 6y ago
There doesn't need to be selection pressure for a mutation to spread, it just needs to be no disadvantage to develop it
- pfdietz 6y ago
  With no selection pressure a gene will not from 10% to 30% in a few generations. That requires a tremendous selective advantage.
  - ip26 6y ago
    Well, or it just needs to be a dominant gene.
    - pfdietz 6y ago
      That makes absolutely no difference.
    - jessaustin 6y ago
      The gene didn't become dominant in the last several generations.
trhway 6y ago
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.
SamReidHughes 6y ago
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.

ceejayoz 6y ago

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.

dghughes 6y ago
>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?
- fleischhauf 6y ago
  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..
  - learc83 6y ago
    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.
  - deleted 6y ago
    [deleted]
  - deleted 6y ago
    [deleted]
- Someone 6y ago
  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 https://en.wikipedia.org/wiki/Median_artery), and https://radiopaedia.org/articles/persistent-median-artery-of-the-forearm 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.
  - leephillips 6y ago
    More stamina when composing romantic emails → greater chance of reproduction.
fleischhauf 6y ago
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!
Gupie 6y ago
But that does not increase, in any way significantly, a person's reproductive success.
Someone 6y ago
That second part seems unlikely to me. I would guess the percentage of people that’s beneficial to is extremely low.
knolan 6y ago
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.

tronbabylove 6y ago

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.

fs_tab 6y ago

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_increased_prevalence_of_the_human_median_artery_of_the_forearm_A_microevolutionary_change 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.

oh_sigh 6y ago
No need to request: https://scihubtw.tw/10.1111/joa.13224 https://scihubtw.tw/10.1111/joa.13224

heeen2 6y ago

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

pfdietz 6y ago
With no selection pressure a gene will not from 10% to 30% in a few generations. That requires a tremendous selective advantage.
- ip26 6y ago
  Well, or it just needs to be a dominant gene.
  - pfdietz 6y ago
    That makes absolutely no difference.
  - jessaustin 6y ago
    The gene didn't become dominant in the last several generations.

trhway 6y ago

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.

SamReidHughes 6y ago

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.