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.
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).
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.
Doppler ultrasound can be used to measure blood flow; I've seen it used in prenatal scans to check for heart defects. I'd think it would be straightforward to use it to locate arteries in the forearm.
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.
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."
This 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.
Why wouldn’t the gaming morph to stuffing the lottery? Submit similar grants with different PIs, different combinations of researchers, slightly different focuses or plans.
Apart from the issue of grant stuffing, I have a strong suspicion that 25% is an extremely low number and even among those grant applications that pass obvious flaws there is still an extremely large variance in quality.
To put it another way, imagine if a strategy for funding software development was to take every piece of software that compiled and then randomly choose among them to fund. This seems like it's ripe for exploitaton and hard to fund meaningful software development (especially coherent ecosystems).
Similar dynamics would probably be at play for research.
Having personally read through a large number of grant applications I would say 25% is about accurate. It really doesn’t change anything if we were to raise the threshold to say the top 50%. The key to success is to remove the human element of trying to determine what is a top 5% grant from a top 10% grant. This has been proven to be impossible.
You can stop the grant stuffing gaming by limiting the number of grants people can apply for every year.
Don't forget that the people writing the grants are heavily influenced by what is required to obtain a grant. If the aim of writing a grant becomes to not be in the bottom 25%, than the average quality of grants will go down.
I think it has not been proven to be impossible to determine the difference between a top 5% and a top 10% grant, it has just been proven that the current system does not do that. In trainings for grant applications it is often mentioned that members of grant committees spend extremely little time per grant proposal, which I imagine is just sufficient to weed out the bottom 25% proposals (those that contain obvious flaws)
It doesn’t matter if the average quality of the grants goes down (it would actually be a good thing if it reflected less time being spent on grant writing), what matters if the average quality of the science goes up. Grants are a means to an end, not an end in themselves (administrators feel different about this I will admit).
It has been proven that grant reviewers can’t agree amongst themselves what are the top 5% verses the top 10%. Having personally gone through the process as a reviewer I can identify the difference between a good and a bad grant, but I can’t with any reliability determine the difference between a top 5% and a top 10% grant. Once you get into the top 25% of grants the ranking gets very arbitrary. I might like one grant more than another purely because I like the area more, but my taste should not be the criteria on which grants are chosen.
The crazy thing is all of this is known by everyone involved in the grant process yet everyone continues on as though the system is working.
But 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.
The same approach can be applied to tenure. Set a basic threshold that someone needs to meet, then run a lottery to chose who gets tenure. Would end an amazing amount of unproductive gaming of the system.
This would work if people are roughly equally good above that low bar. But there are vast differences. The current metrics aren't perfect but they do correlate with ability. And as I said, you can't randomize everything, like talk invitations or "followers", collaboration offers, research stay offers at prestigious places, media exposure etc.
Ultimately, most people are driven by a striving for social status and prestige. This is very general and includes money, power, freedom, intellectual influence, access to interesting people to work with and discuss, being taken seriously by intelligent co-experts, being a valued and respected member of the community, whose insights people look out for etc.
This is taboo to say explicitly of course, one must say that it's all internal passion, but people, whether they admit it or not, will have to strive for these things. If they don't, they fall behind.
This goes way way deeper than grants. It's not even just human nature, but a fundamental property of life.
The same is true in dating. You have to present yourself in the best possible way, and those who do have better success.
It's not enough that you and your ideas are good, you have to be able to convince people that you are worth investing in.
You can't forbid people to associate, to form cliques, to keep tabs on who is good and who isn't (and the same for departments and universities) etc, to invite each other to work together.
A grant that led to a sexy result will be considered money better spent, than something that leads to no presentable conclusions.
And beyond the gaming, there are genuine differences in how good a research vision some people have. Top, visionary people vs mediocre incrementalist copycats is a real distinction.
> 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.
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.
> My question is, does their methodology tell apart the following effects: [...]
First and foremost, their curve fitting, disguised as race-agnostic methodology, ignores the number of studies of the median artery in Africa 100 years ago (zero) and now (many).
> 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.
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.”
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.
Those 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.
If you're talking about a mutation that will increase the reproductive success of your children(or more likely grandchildren in the case of reduced chance of a heart attack), then the advantage would have to be even greater because of the high chance that your descendants don't have the same mutation.
I'm not saying there's no natural selection occurring, but that saying that heart disease is the #2 killer of Americans out of context likely overstates the selection pressure heart disease causes.
Yes, but the vast majority of people who die from heart disease don’t develop it until they are older. Which is why it’s misleading to talk about it being America’s #2 cause of death when discussing evolutionary pressure.
Target heart rate declining and blood pressure rising with age in no way implies that most people who later die of heart disease are somehow less reproductively fit when they are younger.
You say that, but the connection seems likely which is my point. The indirect symptoms of heart disease such as loss of athleticism and cognitive function would be important.
Heredity is one of the stronger predictors of heart disease so it’s got a strong genetic component beyond diet and lifestyle. So, it’s really just a question of how early meaningful symptoms show up as the physical differences already exist during people’s reproduce years.
It seems like an obvious test if do differences in Forearm arteries have fewer heart attacks. And do they correlate with higher blood pressure in people’s 20’s to 30’x.
>You say that, but the connection seems likely which is my point. The indirect symptoms of heart disease such as loss of athleticism and cognitive function would be important.
Only if as you say the meaningful symptoms show up during common reproductive years.
So far I see no evidence that that is the case.
>Heredity is one of the stronger predictors of heart disease so it’s got a strong genetic component beyond diet and lifestyle.
Again there is no evidence that it is common that hereditary heart disease that generally affects people 50+ has meaningful symptoms during reproductive years.
And there is even less evidence that these symptoms are meaningful enough to impact fertility to such an extent that it creates significant short term evolutionary pressure.
You're taking 1 condition which is common in later life and saying: well maybe some people with that condition actually develop it earlier in life, and just maybe some people that develop it earlier have some externally significant symptoms, and maybe some of those people have specific symptoms that would make them less likely to reproduce all else being equal.
Each step of that funnel is a complete unknown, and each step diminishes the overall impact that genes that control the most common forms of hereditary heart disease have on reproductive fitness.
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.
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...
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 can’t even decide where to start picking apart these arguments... it’s mostly just a “the skies are falling” fear-trip occurring whenever some significantly new status quo emerges.
Sure, literacy made people less willing to spend their lives farming for a pittance, but we managed to industrialize farming and some of those peasant families contributed to society more than a couple loads of bread.
Let’s put it this way: we’re on the path to fully disassemble cellular processes, we won’t need natural selection to tune our immune system when we can design a better one ourselves
Those are valid points. However, immunization has virtually eradicated entire families of diseases with serious, life-altering side effects. I would argue that the short-term benefits outweigh the potential long-term consequences in this case, especially if we continue to vaccinate children against these diseases.
That being said, I think it's far more likely that genetic conditions and predispositions to disease will be resolved through genetic engineering, not natural selection.
Yea, it's not obvious whether we should be sacrificing people today to maybe save future people, especially if we can genetically engineer it all away. But our ancestors (or rather the humans that weren't our ancestors) were certainly sacrificed for our benefit.
I don't think we'll evolve our way out of genetic diseases or we would have already. Rather, it seems like we'll degenerate into higher rates of them without ongoing selection pressure keeping the rate low.
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.
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.
evolution itself does evolve. Eusociality or sexual dimorphism, group dynamics and all kinds of complex phenomena obviously weren't present in the primordial soup but are pathways themselves carved out by evolution.
Rate of mutations may change, new mechanisms of evolution may turn up, humans ironically by understanding our genome have acquired the ability to manipulate it in intelligent fashion, and so on.
What has led you to believe that evolution is not itself continuously evolving in each lineage? What do you imagine DNA is for? What do you imagine sex is for? Do you imagine that sexual reproduction always existed, or that it has had no effect on the lineages where it occurs, or their relative prevalence? How do you imagine those lineages became so prevalent, among multicellular organisms?
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
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.
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.
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.
>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.
> 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.
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?
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..
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.
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.
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!
> "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.
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.
> 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.
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.
> 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.
> 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).
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.
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.
* 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".