Investigating the case of human nose shape and climate adaptation (2017)
journals.plos.org
journals.plos.org
Quite fascinating topic to wonder about: how long will it take for the modern era to genetically change us ?
We have diseases and genetic defects, among other impacts through modern behaviors and environments/toxins, which are also retained in the genetic mutational load. We even have a whole lot of energy and human activity working to counter evolutionary pressures and assure those accumulated mutational loads remain in the genetic code.
Ignoring genetic drift and taking into account only natural selection, all that's needed is differences in fitness, i.e. differences in how much an individual contributes to the gene pool of future generations.
Not sure if he's the originator, but I'm pretty sure I learned about it in a Richard Dawkins book.
Like the traits must have already been present in some lower frequency pre crisis, and the crisis distills the traits which are selected for by the crisis.
So probably less evolution moves faster during crisis and more that there is an interesting survivorship bias related to crisis when analyzing the change of a species over time.
Evolution is not primarily driven by the mutation rate. It's primarily driven by differential success of already-existing genetic variation. Over the very, very long term, you need mutation to be the source of that genetic variation, but over the short term mutation is mostly just harmful, and this:
> Like the traits must have already been present in some lower frequency pre crisis, and the crisis distills the traits which are selected for by the crisis.
is correct.
> So probably less evolution moves faster during crisis and more that there is an interesting survivorship bias related to crisis when analyzing the change of a species over time.
This is conceptually wrong; in this context "survivorship bias" bears a technical name you've probably heard of, "natural selection". A stronger survivorship bias means faster evolution.
I only mean, natural selection is the survivability of e.g. a nose shape trait across generations, which can happen via reproduction, early death, etc and it’s not about survivability of the person WITH the nose except to the extent that facilitates the former
Survival of the fittest traits
There are ways we could avoid losing most of that survivability but of course they are wildly unpopular such as actively discourage people with terrible inheritable diseases to procreate (e.g. ALS, Lupus), favor reproduction of people with both higher intelligence and physical skills (e.g. goverment subsidies for their parents, tied to their children grades and general well being)
Humans aren't individuals, no matter how certain blips of modern culturalism pretend.
Note that sexual selection selects for health, wealth and reputation. Women are doing most of the selection here.
Take just the easiest to measure of those factors, wealth. Per your hypothesis, wealthier men should have more babies. Do you have any evidence that wealthier men have more babies?
In fact, it's quite the opposite. There is a strong inverse correlation between wealth and number of babies. Both globally [1] and in the US [2]. There is some data that you can seek out that will suggest the trend is reversed in some first-world countries in the past couple of years, but that's no where near enough time to draw conclusions.
Is there real evidence that men with greater "health" (besides the obvious, of, say, having a crippling disease) or "reputation" have more children?
I'm sorry, but this sounds like "women only chose alpha males" junk to me.
1. https://en.wikipedia.org/wiki/Income_and_fertility
2. https://www.statista.com/statistics/241530/birth-rate-by-fam...
Women do marry and prefer richer men. Hypergamy is scientifically true, you can look it up if you want. But birth control changes the outcome even though hypergamy is an influencing factor.
In addition I said health and reputation are factors. So a man with good health but low wealth has one positive factor in his favor.
I feel your entire reply is rude and over the top. Calling my statement junk is not conducive to discussion.
The thread is about evolution, and sexual selection in the context of evolution generally implies having an evolutionary fitness. I missed the part about birth control, since then we're not really talking about whether sexual selection is having a role in human evolution.
In the context of sexual selection affecting evolutionary fitness, it seems clear that there is an inverse relationship between wealth and number of offspring.
I am not sure if there are any scientific studies purporting to link "reputation" and either marriage or offspring. Do you know of any?
This inverse is caused be birth control and economic circumstance. For the poor person, more kids means more kids on the farm to work. So the poor person chooses to have more kids via not using birth control.
For rich people in rich areas, more kids equals more college tuition to pay. So the rich person chooses to have less kids via using birth control.
That's what causes it. I'm too lazy to cite sources but this comes from anthropology 101 it's textbook stuff. And like most anthro stuff the studies are qualitative, so take from it what you will.
>I am not sure if there are any scientific studies purporting to link "reputation" and either marriage or offspring. Do you know of any?
Just google it. I hit a result here:
https://en.wikipedia.org/wiki/Hypergamy
It's even in the wikipedia. It's also quite obvious if you've interacted with a lot of women before.
Look I know there's this woke movement that likes to cover up a lot of the dark stuff surrounding human behavior. Men and women have dark sides and this is just one of the darker things about women: Hypergamy. I think the thing that makes it more intriguing then the dark side of men is that culture and society basically masks this fact about women.
You see the double standard here? You can call men dumb and into boobs and butts and physical pleasures but to even mention something superficial about women you became all reactive about it like it's sexist. Men ARE into boobs and butts, that's just a fundamental truth and it's not sexist. Neither is this. It's also obvious.
Broadly, yes--wealthy people have more kids than poor people [1]. The confounding variable is market opportunity: when opportunity is high, the opportunity cost of kids goes up, which causes wealthier people to have fewer kids.
The study cites a dozen or so papers saying:
> Within contemporary Western populations, wealthier, higher status men tend to have lower fertility. In low and middle-income countries where populations are at different stages of this transition, women in wealthier households have fewer children on average. Over the course of the fertility transition, wealthier families also reduce their fertility earlier and more dramatically than the rest of the population.
They then essentially do a big regression analysis to say that if you take your material wealth and your education together, which they call your market opportunity, there is a strong negative relationship between that and fertility. Then if you take that same material wealth and your agricultural wealth together, there is a weaker positive relationship between that and fertility. So basically agricultural wealth (land and livestock) may be weakly correlated with having more kids, but other kinds of wealth aren't.
(And that's ignoring the fact that the chi-squared analysis said that their model was a poor fit anyway, but they hand-wave that away by saying that that's probably just because they had too much data.)
Finally, and importantly, the original statement by GP was that there was a sexual selection that favoring rich men. That is, that rich men would be selected by women and have more children. This study does not address that at all, as it measures household wealth, household education and number of children per woman, not per man.
it's not about killing people before reproductive age, it's about absolute numbers of offspring born. dying before reproducing ensures that number stays 0, but you can still hit sexual maturity and not reproduce.
plus there is a fertility window -- after 50 most humans, male or female, ain't having kids (a handful of rockstar types whelping babies at 80 notwithstanding).
there is a TON of meaningful pressure in our environment, like the inability to have a living wage reducing how many Gen Z's are marrying and having kids.
Technically, it's about averaging offspring (weighted by your genetic contribution to them) across all of time. If you have 30 children, and all of them starve to death before reproducing, you've reproduced less than your neighbor with the one child and one grandchild.
But that's impossible to calculate, so mostly we just have to work with number of children. This detail, though, is something you might want to keep in mind when looking at reports of "effective population" in the past. Any actual population in the far past who end up being wiped out in the middle past are excluded from the "effective population" that we calculate.
If a population used genetic engineering to collectively ensure their genetics didn't change, no mutations, no other populations involved, then... I guess? Otherwise, there is this staggering multitude of influences.
Living longer and reproducing longer is a huge weight on the scales of evolution. Why does anyone need to die early for it to work?
Empirically false [1]. The median artery is a poignant example from the industrial era [2].
[1] https://en.wikipedia.org/wiki/Recent_human_evolution#Early_M...
My understanding is that evolution is specifically directional change in response to a pressure, not random drift or coincidence.
Is it accurate to say a trait evolved if the change in prevalence is entirely incidental and tied to a second Factor?
Is it accurate to say a trait evolved if the change is a regression to the mean in the absence of pressure?
I went looking for papers on why the median artery might be selected for, and one hypothesized that it may be grouped with, fetal deformities, such as spina bifida, which are increasing not because they are advantageous, but because adverse selection pressures are diminished.
Another hypothesis is that the variation in median artery is not reflective of a change in genome, but change in environmentally triggered gene expression associated with maternal health.
Nobody seems to have studied the effects of a persistent median artery on dexterity (important amidst increasing literacy and now phone/computer use) or forearm circumference (looks hot).
Evolution just means change, and it includes genetic drift. In common parlance, 'evolution' generally implies improvement, but that's not the technical definition.
War and disease. Rich countries can afford defence and healthcare. Poor countries cannot. (Within rich countries, the kids of the rich see war and disease less. They're more likely to be in offices, not on the battlefield and they're more likely to be educated and vaccinated.)
And even rich countries have periodic selection pressures. Natural disasters. Pandemics. Addiction epidemics. Propensities towards violent altercations or risk-taking behaviour. (Exhibit A: young men in cars.)
Did the authors propose a counter-evolutionary pressure, to favor a shorter nose in more humid environments?
It's possible that the mechanism would be as simple as "it requires more resources to maintain a longer nose," but I'm also wondering if they suggested anything.
> We find that variation in both nares width and alar base width appear to have experienced accelerated divergence across human populations. We also find that the geospatial distribution of nares width is correlated with temperature, and absolute humidity, but not with relative humidity. Our results support the claim that local adaptation to climate may have had a role in the evolution of nose shape differences across human populations.
I really wonder how nose shape can affect evolution. What is the mechanism? How can better air lead to higher numbers of successful offspring or fatalities?
Some environmental parameters are temperature and absolute humidity. But there are also significant differences in sex when a other parameters are equal. So perhaps the correlation is not so straight forward.
Breathing through your nose in the cold while walking to class was one of them. I heard this a lot back then, the logic being as you propose; that it just gives the cold air a bit more time to warm before it reaches your core. Adding to that, you were also supposed to breathe slowly, rather than taking fast, gulping breathes. That just added to the reasons to avoid over-exerting yourself in the cold, which poses other risks.
Other stuff had more to do with choice of clothing material, layering, etc, but that's not really applicable to this conversation.
Interestingly, while it still does get cold where I live now, nobody really pays attention to these rules. I'd say the difference between the two areas is something like -5F on average, give or take. I am not sure how significant that is.
After extensive nasal surgery in 2009 this became an option for me again, after over 20 years when it wasn't.
I discovered a less-discussed rider: yes, it seems gentler on the lungs to breathe in through your nose in sub-zero weather, but there is a condition: you should breathe out through your nose as well.
Exhaling warms the structures in the nose so it can warm the next inhalation.
But, for me, that same sub-zero weather often causes my nose to make more mucus -- so breathing both in and out means a lot more use of a handkerchief, or a nasty snotty moustache.
It's sometimes simply not worth it. :-/
Discussion here from 2019 about heat exchanger masks seems relevant. They warm incoming air using the heat from outgoing breaths.
Try running XX hours after an antelope and report back, most animals aren't optimised for long distance, humans are, you can hunt most things by following them and waiting for them to collapse, surely having better air intake helps. It might be something as dumb as more antelope meat = more social points = you get to bang more.
Why do 70%+ of the world population has brown eyes ? It offer marginal UV resistance but nobody becomes blind or sterile because they have blue eyes, certainly not before they can reproduce. Chances of reproduction can also be dictated by other things like attractiveness, and these are also very dependant on cultures and time periods.
The guy who brings home the most food will have the most surviving children.
He will also be very attractive to women.
According to this theory, the rhythm was to walk a long long time and maybe hungry too, then a burst of activity, then stuff your face, then pass out for a while, then repeat. It seems logical & sensible & probable.
Evaporation is a big factor in both controlling temperature and water retention/loss ( that's why dogs pant in hot weather ).
Remember the surface of your lungs are topologically on the outside - they are large and wet and are sensitive to both physical dust etc as well as potential infection.
The nose design has to find the best balance across all these factors ( as well as being important in the sense of smell ).
- harder to find mating partner before earplugs were inventend
- easier for your enemies/predators to catch you in your sleep
Now I wonder if that is in fact some type of adaptation to local climate because the people of the surrounding areas don't seem to have that nose shape to the same extent.