Forearm artery reveals human evolution continues?

https://news.flinders.edu.au/blog/2020/10/08/forearm-artery-reveals-human-evolution-continues/

80 90 6 years ago

news.flinders.edu.au

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• 6 years 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• 6 years 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?

fleischhauf2• 6 years 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• 6 years ago

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

Someone2• 6 years ago

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

knolan• 6 years 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• 6 years 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_tab3• 6 years 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_...

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• 6 years ago

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

heeen2• 6 years ago

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

pfdietz2• 6 years ago

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

trhway• 6 years 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• 6 years 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.

carbocation3• 6 years ago

The 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.”

Retric5• 6 years ago

DNA 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.

carbocation3• 6 years ago

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.

learc837• 6 years 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.

eecc2• 6 years ago

Well, Natural Selection doesn’t necessarily mean that only advantageous genes survive the Darwinian hustle, it can also mean that in the absence of negative external pressure also neutral variations are not systematically culled.

It’s like living in a civilized society; you don’t have to worry of starving tomorrow so you take on making art...

carbocation3• 6 years ago

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.”

lopmotr2• 6 years ago

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.

cm21872• 6 years ago

Similar evolution with no selection pressure:

https://www.independent.co.uk/news/science/wisdom-teeth-evol...

I don’t think Darwinism is scientifically established. It has become a bit of a sacred cow because of its opposition with religion, but it is merely a good explanation compatible with the data. That doesn’t prove it. It may be that life evolves and adapts through other mechanism than mere selective pressure.

mrfusion• 6 years ago

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

slickrick2162• 6 years ago

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.

ncmncm2• 6 years ago

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.

drbojingle• 6 years ago

Why would it stop?

robbomacrae• 6 years ago

Bingo. 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.

Ericson23143• 6 years 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• 6 years ago

"Evolutionary intertia"? Evolution is change, and inertia is the resistance to change... it makes no sense anyway.

Ericson23143• 6 years ago

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.

Izkata• 6 years 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).

Ericson23143• 6 years ago

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

lehi• 6 years 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• 6 years ago

Could 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.

sradman4• 6 years ago

From 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.

jessaustin2• 6 years ago

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.

mci4• 6 years ago

I 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".

danieltillett7• 6 years ago

But 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• 6 years ago

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

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

MeinBlutIstBlau• 6 years ago

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."

tgbugs• 6 years ago

I work with a consortium that is trying to map the anatomy of the peripheral nervous system. My key take home has been that our knowledge of peripheral anatomy at population scale is woefully inadequate. People look at Vesalius and think "oh, that was settled 500 years ago," but as it turns out it seems that we know far more about the peripheral anatomy of our pets and domestic animals than we do about our own.

sradman4• 6 years ago

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.

mci4• 6 years ago

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).

sradman4• 6 years ago

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.

Hopefully this paper will inspire more research involving this interesting phenotype. I'm curious about the population specific prevalence too.

bonoboTP4• 6 years ago

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.

x86_64Ubuntu• 6 years ago

I'm confused about why you would CTRL+F "race".

fs_tab3• 6 years ago

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

mci4• 6 years ago

Here is a polished version of my argument: https://marcinciura.wordpress.com/2020/10/11/bad-medicine-th...

sradman4• 6 years ago

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.

rationalfaith• 6 years ago

Why 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.

Forearm artery reveals human evolution continues?

Related Stories