Forearm artery reveals human evolution continues?

With a limited pool of funding, how would you decide?

If a committee, how would they be chosen, guarding against bias, etc.

Nothing says science needs to progress linearly. Also, sometimes you gotta make the public think lame stuff is magic in an ELI5 way to get them to have a positive opinion on it so that when the government funds these things, people aren't up in arms that millions are spent on that as opposed to lowering their property taxes.

Like Tommy Lee Jones said in Men in Black: "A person is smart; people are dumb panicky animals."

Is there a non-intrusive (and hopefully inexpensive) imaging technique that can be used on a living population rather than depending on cadaver dissection? Doppler, ultrasound, or even modified consumer wrist reflective PPG (like in the Apple Watch) should be able to detect the median artery. I imagine nerves are harder to map.

I once tried to write an algorithm cookbook where the network flow problem would be illustrated by a simplified human circulatory system, and its edge capacities — by the diameters of the major blood vessels (this is how I knew to look for Adachi in this paper).

Besides the diameters being different in autopsies and ultrasounds, it turned out that while the mean diameters of the arteries are generally known, as they are used for diagnosing aneurysms, no source I found cared to publish the mean diameter of, say, the left and right gastroepiploic veins.

Also, even if 90% of people have the prevalent topology of some branching of blood vessels and only 10% have other variants, there are so many branchings that hardly anyone has a "textbook" circulatory system (that is, if the branchings are independent; I have seen no study of their correlations).

Do I understand correctly that their observations are compatible with the possibility that some ethnic groups have more of this phenotype and these ethnic groups are becoming a larger percentage of the world population in general? This would make the story about the artery a red herring.

For example if Northern Europeans started reproducing at a higher rate, could we say that humanity is evolving more and more lactose tolerance? I would say that would be very misleading.

My question is, does their methodology tell apart the following effects:

- The new artery is spreading across the board in various places, e.g. there is a general environmental selection pressure for random mutations in this direction, OR

- Populations that have it or don't have it are reproducing at different rates, possibly for totally unrelated reasons like socioeconomic ones.

You would want to stratify results by race or ancestry, since this allele is probably more prevalent in specific populations.

> The conclusion of the paper is just bad science, not an example of human microevolution.

"Bad science" might be a bit harsh. I read the paper as a call to arms (no pun intended). The data presented in Table 1 is good science but the sample is far too limited to support the paper's subtitle "A microevolutionary change".

It is plausible that a microevolutionary change has occurred (ditto environmental change or no change). We need much larger surveys that span populations and geographies to first establish that a change has occurred and then quantify the causal factors.

Perhaps the fault lies in the culture surrounding the publishing of scientific papers with an emphasis on strong conclusions rather than unresolved questions. Maybe I'm being too forgiving because I was previously unaware of the adult median artery phenotype. Regardless, your criticism is important and appreciated as is tgbug's point that we are lacking data on population wide anatomical variation.

I 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.

> #2 killer in the US it’s likely for the circulatory system to be undergoing rapid change.

Primarily killing people past reproductive age though.

Yes, I agree. I'm mostly responding to the authors' speculation:

> “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 seems like we're on a terrible path with this absence of evolutionary pressure. What's happening to all the babies who survive today that would have died in childbirth had they been born at any time in human history before 100 years ago? Since infant mortality was so high, it must have been an close battle for evolution to keep it under control. Now the brakes are off and whatever mutations were regularly killing babies (and mothers) are now free to propagate to subsequent generations.

Not that that's necessarily a bad thing. We've already evolved to become dependent on technology (cooking, clothing, shelter) and it probably does us good by freeing up our body's resources to do other things better. So perhaps becoming dependent on healthcare for childbirth will eventually happen too and nobody will be worried when women can only give birth by C-section or whatever.

A related issue is immunization. People are so worked up about the politics that they don't want to think about this, but could it be that immunizing ourselves is taking away the evolutionary pressure to maintain a good natural immune system? Multiple generations of measles vaccinated people might end up like the native Americans who were vulnerable from their ancestors having never experienced measles.

This seems like a whole alternative kind of morality - protection of the genes of future generations. But it goes against the popular short term moralities that people have so it seems too objectionable.

I’ve always wondered that. Like why hasn’t evolution itself evolved as well?

Selection pressure probably doesn’t apply to evolution in the present tense as evolution is not a conscious entity. Survival of the fittest could have only a past tense application ie the cause of evolution traits surviving. In this case evolution doesn’t know if 3 arteries is good or bad it just happens those people have more kids and their kids have more kids until one day all the 3 artery people die because of some disease where having 3 arteries means you are more likely to die. This will leave 2 artery people living on and from their perspective looking back it’s then selection pressure.

There is no such thing as "Darwinism" outside of Creationist propaganda.

Evolution by natural selection is directly observed in labs, farm fields, and jungles alike. Biologists are not seeking to "establish" it, but to refine it and place it in context with evolution by sexual selection, by genetic drift, by mutualism, and by other influences less well characterized, not least epigenetics, which acts at the scale of individuals.

I.e., lots of "mechanisms" are known. None contradicts any other. What mix is responsible for a change is often hard to tease out.

Darwin wrote about both natural selection and sexual selection. Which do you imagine to be "Darwinism"?

You would better get your information from people not seeking actively to delude you.

>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?

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!

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.

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.

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

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

Changes 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.

So 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.

Yes, but does using that overloaded word cover anything "superpowers" didn't? I'd think it just adds ambiguity.