[HN Gopher] Recently increased prevalence of human forearm media...
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Recently increased prevalence of human forearm median artery:
Microevolution
Author : bookofjoe
Score : 36 points
Date : 2024-05-25 22:52 UTC (2 days ago)
(HTM) web link (onlinelibrary.wiley.com)
(TXT) w3m dump (onlinelibrary.wiley.com)
| leblancfg wrote:
| I read the following:
|
| > The focus of this study was not to analyse the prevalence of
| the occurrence of the median artery in relation to ethnicity,
| geographic origin or variations by sex, but to identify the
| global trends in its occurrence.
|
| and thought "well that explains the astronomical precision of the
| p-value, they didn't take ethnicity into account!". You would
| expect to see variation prevalence vary by ethnicity, no big news
| here.
|
| But no! Thinking about it more, that's exactly what is says on
| the tin: global ethnic populations changed in the last ~140
| years, and with it, the prevalence of generic variations. Makes
| perfect sense -\\_(tsu)_/-
|
| edit: I mean... assuming the causal link ofc. I'm assuming this
| makes more sense than some kind of evolutionary pressure that is
| selecting for forearm median arteries.
| akdor1154 wrote:
| Simpson's paradox...
| penteract wrote:
| From section 4:
|
| > The present study used an Australian sample of European
| origin. These results were comparable to those reported in
| black South Africans, their white counterparts and Malaysians
| of similar birth years; all these groups had a prevalence of
| approximately 30%
| aredox wrote:
| We need to retire the idea that evolution has a goal, or that
| evolutionary pressure explains everything. There are tons of
| things in the human body that are very suboptimal or are purely
| accidental, from the tons of "junk" DNA, our difficult
| birthing, the appendicitis, wisdom teeth, the way our knees
| fold, differences in earwax, etc, etc.
|
| https://en.m.wikipedia.org/wiki/Human_vestigiality
|
| https://www.scientificamerican.com/article/no-humans-have-no...
|
| "Evolution" is just a (fairly tautological when you think about
| it) observation that "traits that manage to get passed on,
| subsist". It weeds out very bad traits, but the rest? It's just
| a giant lottery, not a great design with a teleological goal of
| "improving".
|
| (And the human species has been short-lived so far, and may
| wipe out themselves without the "help" of a meteorite. In the
| same vein, cockroaches could be argued to be the pinnacle of
| evolution.)
| IshKebab wrote:
| Evolution does have a goal - spreading genes. Of course when
| we say "it has a goal" that doesn't mean it intelligently
| plans how to get there. Nobody* thinks that.
|
| I think what you probably meant to say is that evolution
| isn't a perfect optimiser.
| philwelch wrote:
| > There are tons of things in the human body that are very
| suboptimal or are purely accidental, from the tons of "junk"
| DNA, our difficult birthing, the appendicitis, wisdom teeth,
| the way our knees fold, differences in earwax, etc, etc.
|
| Right, but evolution also can explain those; many of these
| are tradeoffs for things that do deliver benefits. Difficult,
| premature births are the cost of big brains, for instance.
|
| > "Evolution" is just a (fairly tautological when you think
| about it) observation that "traits that manage to get passed
| on, subsist". It weeds out very bad traits, but the rest?
| It's just a giant lottery, not a great design with a
| teleological goal of "improving".
|
| The tautological explanation is extremely powerful, because
| it means even a small variation that delivers a marginal but
| consistent advantage is going to be selected for. For
| instance, a person with dark skin can survive in Northern
| Europe, and a person with light skin can survive in sub-
| Saharan Africa, but the ideal skin tones for those regions
| that optimally trade off vitamin D production with protection
| against skin damage from the sun are probably pretty close to
| the ones typical to their indigenous populations.
|
| The actual catch is that there's a lot of path dependence and
| all changes are stepwise. You can't just install a new trait
| or body part that's been designed from scratch; it has to
| evolve from an earlier, similar thing. If you look at the
| bones of your hand, the bones of a bat's wing, and the bones
| of the front paw of a dog, the bone structure is basically
| the same; it's just by changing the proportions that you can
| get the structure of a flapping wing, a front foot, or a hand
| with an opposable thumb.
| ano-ther wrote:
| Are we seeing
|
| 1 A random mutation that is "testing the waters" if this brings
| some evolutionary benefits?
|
| 2 A mutation that already provides a benefit? (Which one would
| that be?)
|
| 3 A mutation that is neutral and is neither beneficial nor
| detrimental?
| FrustratedMonky wrote:
| What is the environmental pressure? Just a mutation by itself
| doesn't spread, there should be some advantage? Shouldn't there?
| napoleongl wrote:
| It's enough that there is no decrease in the success of the
| offspring really. They don't have to be more successful, just
| not less.
| bhickey wrote:
| Under Hardy-Weinberg equilibrium we wouldn't expect a trait
| to go from 0.1 to 0.3 in a large population in four
| generations. This suggests that the trait is subject to
| selective pressure.
|
| There are a lot of potential causes. In my estimation the two
| most likely causes--
|
| First, hitchhiking. The mutation could be near some other
| beneficial mutation. The closer genes together on a
| chromosome the less frequently they'll be separated by
| crossing over events.
|
| Second, it could have some other, presently unobserved
| cardiac effect that reduces infant or maternal mortality.
| FrustratedMonky wrote:
| My joke pet theory is that it helps with mouse control on
| PC's.
|
| We are living our whole life at a desk, it is providing
| extra endurance for clicking.
| mometsi wrote:
| Better-nourished mothers => chonk fetuses => thicker forearms =>
| increased utilization of arterial supply in the immediate
| environment of the the fetal median artery => median artery is
| less likely to atrophy during a critical period of gestation.
|
| No genetic mutations necessary.
| owenversteeg wrote:
| >Analysis of the literature showed that the presence of the
| median artery has been significantly increasing (p = .001) over
| time, from approximately 10% in people born in the mid-1880s to
| approximately 30% by the end of the 20th century.
|
| That is incredibly fast! That's three generations and change,
| which I find suspicious... if it indeed is progressing at that
| rate then I would be quite shocked to learn that the cause is
| purely genetic.
|
| As another comment noted, "It's enough that there is no decrease
| in the success of the offspring really. They don't have to be
| more successful, just not less" - except for the prevalence to
| change that rapidly is very unusual. In the famous story of the
| peppered moths, the first black moth was collected 1811, they
| were about 50/50 in 1864, and they were at 98% in 1895. It took
| until 2003 for the melanic phenotype to fall to around 10%. A
| peppered moth generation is one year, versus a human's twenty-
| seven, and the reproductive pressure was massive (a white moth on
| black trees can't hide and is easily eaten by birds; I can't
| imagine anything similar for humans.)
|
| Also quite interesting for the HN audience: >persistent median
| artery has been suggested to cause pain in carpal tunnel syndrome
| (Barfred et al., 1985; Lisanti et al., 1995)
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