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Forearm artery reveals human evolution continues?
- iheartblocks 6y agoThis 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 agoRight 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 agoReplacement 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 agoIf 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.
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- Someone 6y agoI 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 agoMore stamina when composing romantic emails → greater chance of reproduction.
- fleischhauf 6y agoSo 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 agoBut that does not increase, in any way significantly, a person's reproductive success.
- Someone 6y agoThat second part seems unlikely to me. I would guess the percentage of people that’s beneficial to is extremely low.
- knolan 6y agoThat’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 agoI 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 agoIf 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 agoNo need to request: https://scihubtw.tw/10.1111/joa.13224 https://scihubtw.tw/10.1111/joa.13224
- heeen2 6y agoThere doesn't need to be selection pressure for a mutation to spread, it just needs to be no disadvantage to develop it
- pfdietz 6y agoWith no selection pressure a gene will not from 10% to 30% in a few generations. That requires a tremendous selective advantage.
- ip26 6y agoWell, or it just needs to be a dominant gene.
- pfdietz 6y agoThat makes absolutely no difference.
- jessaustin 6y agoThe gene didn't become dominant in the last several generations.
- trhway 6y agofrom 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 agoLet'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.
- carbocation 6y agoThe selection pressure on three versus two arteries feeding the hand has to be so incredibly small (in terms of survival to reproduction in humans) that I am having a hard time imagining how this story has any causal plausibility. Edit to be more clear about what in the article I'm responding to, it's this: > Dr Teghan Lucas from Flinders University says ... “This increase could have resulted from mutations of genes involved in median artery development or health problems in mothers during pregnancy, or both actually. If this trend continues, a majority of people will have median artery of the forearm by 2100.”
- Retric 6y agoDNA isn’t so neat as to cleanly separate every change. Thus this could be related to a host of changes that collectively represent a noticeable advantage. With circulatory issues being the #2 killer in the US it’s likely for the circulatory system to be undergoing rapid change. Increased blood flow to the hand may mean a more efficient circulatory system increasing athletic performance and lowering disease risks etc.
- carbocation 6y agoI agree. There are plenty of reasons why this could be happening, including reasons that have nothing to do with any sort of selection at all. I've updated my comment to clarify what I'm responding to.
- learc83 6y ago> #2 killer in the US it’s likely for the circulatory system to be undergoing rapid change. Primarily killing people past reproductive age though.
- HNAwayGone 6y agoThose people still influence the young, though. They have a huge impact on their young childrens' diets and habits, and I think epigenetics can throw a wrench into things by affecting how genes are expressed based on environmental factors.
- drbojingle 6y agoWhy would it stop?
- robbomacrae 6y agoBingo. If anything it would speed up with the population bloom and given society has A: changed our selection priorities and B: made it easier to survive allowing dna to jump out of the local minima we might otherwise be stuck in. Being able to afford for a few steps up hill might find a new valley with a deeper minima.
- Ericson2314 6y ago> Humans haven’t developed mutations or superpowers just yet, but a new study shows our species is still evolving in unique ways and changes in natural selection could be the major reason. Ewwww. Why is university press the worst? If we are still evolving and this isn't just about genetic recombination then by definition mutations are involved. Also the publicist writes > This evolutionary trend will continue in those born 80 years from today, with the median artery becoming common in the human forearm. Wat. "Evolutionary intertia" probably has been defined by someone, but it's not that. It looks like this is a doubl-wammy misinterpration of the following quote, also from the press release: > “This increase could have resulted from mutations of genes involved in median artery development or health problems in mothers during pregnancy, or both actually. If this trend continues, a majority of people will have median artery of the forearm by 2100.” It could involve mutations and the trend could continue.
- ffhhj 6y ago"Evolutionary intertia"? Evolution is change, and inertia is the resistance to change... it makes no sense anyway.
- Ericson2314 6y agoSo I'm totally making this up but if interia is about the rate of change being the same, I can imagine a population bottleneck forcing more change as the remaining population finds a niche.
- Izkata 6y ago> Ewwww. Why is university press the worst? If we are still evolving and this isn't just about genetic recombination then by definition mutations are involved. The use of "superpowers" alongside it indicates they're referring to pop culture mutations (in the sense of the X-Men).
- Ericson2314 6y agoYes, but does using that overloaded word cover anything "superpowers" didn't? I'd think it just adds ambiguity.
- lehi 6y ago> "Other examples of human anatomy changing over time, include the prevalence of spina bifida occulta (opening of the sacral canal), abnormal connections of two or more bones in feet, increasing absence of wisdom teeth, thyroidea ima artery (branch of the aortic arch) – decreased over time, disappeared completely by the end of the 20th century) and fabella (small bone in the back of the knee joint – increased over time)." Many of these, and the headline artery, appear to be newly retained neotenous traits and/or atavisms. It reads similarly to a list of physical differences between domestic dogs and wolves.
- rthomas6 6y agoCould this be an epigenetic/gene expression change caused by increased use of our forearm and hand muscles? For instance, how I'm typing this right now, and how children write a lot more than they used to.
- sradman 6y agoFrom the paper's Introduction: > The regression of the median artery commences at approximately the eighth week of intrauterine life. However, the median artery persists in a considerable number of foetuses of gestation ages 13–38 weeks, in newborns and infants and in adults. I'm guessing no to epigenetics unless it involves a change in the intrauterine environment.
- jessaustin 6y agoChanges to the intrauterine environment (which is affected by the larger environment that has seen significant changes) are vastly more likely than selection pressure of the strength proposed in TFA. More likely yet is that this is a spurious interpretation of bad data. The anatomists of centuries past weren't looking at the median arteries of all humans.
- mci 6y agoI have procured a PDF of the paper. Ctrl+F race finds nothing in it. The authors treat e.g. these results equivalently: * Adachi, B. (1928) Das Arteriensystem der Japaner. Kyoto, Japan (8.00%) * Kodama, K. (2000) Arteries of the upper limb. Tokyo, Japan (8.2%) * Henneberg, M. and George, B.J. (1992a) High incidence of the median artery of the forearm in a sample of recent South African cadavers (27.10%) * Cheruiyot, I. et al. (2017) Prevalence and anatomical patterns of the median artery among adult black Kenyans (59.68%) To me, a more plausible explanation is: "as time passes, anatomical studies cover more diverse humans".
- danieltillett 6y agoBut this hypothesis is not going to get you sexy headlines and your next grant funded. If we don’t fix the problems with grant funding and the resulting imperative to publish or perish we are going to kill science.
- tyre 6y agoWith a limited pool of funding, how would you decide? If a committee, how would they be chosen, guarding against bias, etc.
- danieltillett 6y agoThis problem has been solved long ago. Screen all grant applications to weed out the flawed approaches (the bottom 25%) and then run a lottery on the remaining. If there is nothing to game, the gaming stops.
- bonoboTP 6y agoBut it goes way deeper than just grants. Who will get tenure for example? Citations and publication counts are used for many many things. Also, making your findings sexy is not just done to improve metrics for promotion and grants. Sexy research also draws attention among experts and lay media alike. They will be invited to give talks at conferences and seminars etc. more if their findings are exciting.
- rationalfaith 6y agoWhy would mutations ever stop? Also evolution is used ad nauseum it's annoying. Is cancer mutation evolution? Are hereditary sicknesses evolution? Mutation seems more objective and neutral term here.