It seems self evident to me that evolution is a natural process that continues to this day. Surely, humans are still experiencing it. It’s also my understanding that evolution isn’t synonymous with “progress”, but is simply adaptive responses to one’s environment.
So how might our modern society be impacting our species’ development?
In thinking this through, one of the first things that occurs to me is that being materially successful doesn’t necessarily correlate with having lots of offspring. Wealthy and well educated people may have fewer children than poorer families. So, evolutionary development may not be dictated by the prevailing diets or lifestyle.
If poorer people have more kids (and that’s just a guess), does that fact portend anything for humanity that might end up in our genetic code?
What about the modern ability to travel globally? Or the resultant mix of cultures, nationalities, and ethnicities? Is that something that will be changing humans over the centuries? Surely, the “races” may not be the same in a few hundred years - does that count as evolution? Will it result it certain genetic anomalies or immunities also?
Or has modern medicine, which has dramatically reduced infant mortality overall, ultimately undercut any impact that evolution would otherwise have on our species? Am I simply naive to think that there is some meaningful human evolution in modern times?
What’s your thought? How are humans evolving? Thanks to all who reply.
Evolution by natural selection is much slower than the current pace of advance of human technology. Under the natural selection paradigm, the genes that get into the next generation come disproportionately from those who are better at surviving and reproducing. But this will be irrelevant when we can directly manipulate the genome to make it what we want it to be.
If you want to ask how much evolutionary change there has been during the whole of modern civilization… 5,000 years is about 0.1% of the time since the divergence between humans and chimpanzees. So that gives you a sense the order of magnitude of genetic difference between a modern human and a human born at the dawn of modern civilization.
So without yet venturing to comment on the specifics of what changes may have taken place, I think we can be confident that the changes have probably been quite minor.
A common misunderstanding about Darwinian selection is that is has to do with how many offspring you live. It doesn’t. It’s about how many survive to reproduce. Someone who has 10 children but not one of them survives to have more children is not an evolutionary winner. Someone who has 2 children who then go on to have 2 children who then go on to have 2 children who then… that’s a Darwinian winner.
Only if that went on for a VERY long time. Tens of thousands or even hundreds of thousands of years.
Global travel means global spread of disease - as we have all recently experienced. That exerts pressure on populations in regards to immune systems. That is not, however, a change easily perceived by human beings. It does, very much, have an impact - there were massive die-offs of Native Americans due to the arrival of European/African diseases along with the arrival of people from Europe and Africa. More recently, people who are unusually susceptible to covid-19 are experiencing elevated mortality. Genetics does affect immunity - there are people in both Europe and Africa who carry a genetic resistance or even actually immunity to HIV - but they are different mutations on each continent. The one from Europe is associated with having ancestors that survived (or were immune to) the Black Death. Not sure what’s going on with the one from Africa, but a similar past plague could have exerted similar pressures on populations on that continent. So yes, immunity is and will continue to be subject to evolutionary/selection changes.
Greater mobility on the part of individuals should also, in theory, result in less inbreeding and certain genetic syndromes becoming less common. They will not entirely vanish. Nor will certainly already uncommon traits like red hair - the genes will remain in the population, it’s just that recessives will be less likely to match up with their counterparts. It will still happen, though.
Infant mortality is not the sole filter for evolution. Doesn’t do your lineage much good for your infants to survive to, say, 25 but never actually reproduce. Reduced infant/child/young adult mortality tends to lead to fewer offspring overall but more resources put into each one, which would make us even more K-selective than we already are. If it’s coupled with later reproduction it might lead to eventual longer lives, as low birth rate + later reproduction can result in that. Any that causes earlier/more babies can wind up favoring that over long-term health and body maintenance, reproducing later means sufficient resources have to be put into maintaining body and health to reach that age to reproduce.
Some “recent”, in geological terms, human adaptions/evolution include such things as retaining the ability to digest milk and dairy into adulthood, which apparently is only around 10,000 years old (there have probably always been the odd mutant here and there, but with no advantage it did not persist/become widespread until changes in culture and diet it made it so). Blue eyes in humans is also a relatively recent change as near as modern science can determine.
As to how minor or major such changes are, well, that’s debatable. Certainly there are billions of perfectly functional humans with eye color other than blue, and who can’t digest milk past weaning age. On the other hand, if being able to digest dairy as an adult helps prevent starvation by opening up a new food option, or your blue eyes make you sexually appealing to the opposite sex and as a result you leave behind more children… well, in that case those traits are an advantage. But they would only be so in a particular set of circumstances, like your culture having dairy animals to begin with, or your culture favoring blue eyes instead of preferring a deep, rich brown eye color.
Our current global culture might, over the long term, favor people with greater resistance to toxic chemicals. Depending on how climate change goes, greater heat tolerance might become and advantage. Certainly, increased disease resistance is always a plus, but then, it’s always an arms race between your immune system and the pathogens around us.
So yes, evolution continues to exert and influence over human beings, although it’s not always visible, especially on the time scale of a human lifetime.
Most modern humans have an overbite, where as recently as 250 years ago in the West most humans had upper and lower teeth that aligned. According to this article it’s a result of the western adoption of using a fork and knife to eat. I thought it also had to do with our more modern diet consisting of foods that are much softer and easier to chew, resulting in smaller, less powerful jaws.
This is a really interesting phenomenon, that may also have affected spoken language. But it’s not evolution. There’s no genetic change, it’s a behavioral/cultural change, eating different foods causes our jaw to develop differently.
Is our eyesight as a species getting worse? Someone like me – with my horrendous vision – should have walked off a cliff and not spread the crappy-vision gene. Is modern life (TVs, iPhones, etc.) making our eyesight worse and being reinforced by myopic people breeding? Genetics is not my forte.
When you’re looking at just slight differences in reproductive success, evolution is going to take a long time. For more rapid evolution to occur, you usually need a high rate of death among people who do not have the trait in question. So if you’re looking for significant evolutionary change in the last few thousand years, a prime candidate will be genetic susceptibility to diseases that have wiped out millions of people - the constant evolutionary arms race with pathogens. Another place to look would be mutations that have helped people survive widespread famine, or at least to have adequate nutritional resources to successfully raise children when most people could not.
Part of the reason that evolution is likely to be rather slow in modern civilization is that we just don’t die enough. Life is no longer so brutal.
It’s tempting to see statistics on the rise in certain chronic diseases like diabetes*, etc. coming from the fact that we now have medical treatments allowing patients to live longer lives, where previously they would die pretty early, often before reproduction age. So a definite evolutionary effect.
But I don’t think such medical treatments have been effective long enough to have an evolutionary effect. In diabetes, for example – insulin has only been available for what, 5 generations? That’s barely a blip on the timescale of evolution. Maybe it will be relevant in a few thousand years.
*PS. assuming this rise is:
an actual increase, not just due to better diagnosis & reporting, and
not due to other causes, like our modern diet re; diabetes.
I think in this particular case, discussing modern humanity, people are making the implicit assumption that, given current medical and scientific technology, most if not all children born will generally reproduce. Which seems like a slightly reasonable, if Western-centric, assumption.
Myopia is another culture-influenced trait. As cultures that used to be hunter-gatherer with most adults having near-perfect vision adopt more modern lifestyles their next generation starts developing myopia. It may be linked to spending more time indoors and doing close-in work, rather than focusing at long distances in the visually diverse and stimulating out-of-doors.
Presumably, if two myopia people reproduced but their children were subjected to a hunter-gatherer lifestyle the children would be far less likely to be myopic.
Also, keep in mind that the modern standard, expressed as something like “20/20”, is a new standard and probably far more precise than in the past. A few centuries ago if your vision was, say 20/30 instead of 20/20 it was quite likely neither you nor anyone else would have noticed. Maybe you’d note that some people could see a little further than you could, but in day-to-day life it would make little to no difference. So some of the increased “bad vision” is due to more precise measuring tools.
Nobody’s mentioned Cyril Kornbluth’s novella The Marching Morons ?
Basically, he suggested that after many generations of civilization, the genes that normally would be weeded out of our pool (think Darwin Awards) are actually managing to reproduce. I also remember a guest lecturer when I took a course on science fiction in college, back in the mid-70’s, who said the same; that we are in essence diluting our gene pool with non-survival genes. There’s a plethora of such traits. Poor eyesight is just one. Hemophilia, susceptibility to diabetes type I or cancer, lower intelligence, even IVF to allow people with poor reproductive abilities to have children… Not to mention minorly debilitating conditions like severe asthma, allergies, IBS, etc - things that would impede someone’s ability to function in the wild. ( Marching Morons was predicated on the theory all the smart, healthy people were selected for emigration to the colonies on new planets, leaving behind the intellectually or physically unfit.)
Indeed, as we see with conditions like Tay-Sachs and Huntingdon’s, now modern DNA tech is in fact helping to weed out the problem for those who care to use it.
Of course, not all such conditions are genetic, but many are. The other point is - it doesn’t matter as long as civilization keeps going. It’s when the supply chain seriously fails for extended periods that the lethal medical problems become problems. I would suggest the number of fit humans continues to be sufficient to ensure the species can survive any bottleneck event.
As for things like “stupidity survives”, that seems to me to have been a problem since agriculture developed. It takes more smarts to hunt than to plant food. yet, there does not seem to be a significant IQ difference between assorted cultures (once we allow for education and nutrition), no matter how many millennia some have been non-hunters. It also smacks of the “welfare queen” debate, and contains racist overtones. Plus, truly brilliant people seem to crop up from the most prosaic beginnings.
But are we selecting for anything, other than being less selective about debilitating conditions? Not that I can see. The only thing I wonder about - reading about the history of the Vikings and Iceland, and discussing agricultural societies, I wonder… there was a time and social situation where the berserker gene (if there is such a thing) would have been advantageous to make more ruthless warriors, but then in a more settled environment, it’s detrimentally disruptive to social order. But is this a hereditary thing, or just social conditioning on controlling a temper?
There are assorted traits that can evolve in lesser time. Some that come to mind -
In the Andes, people who have lived at higher altitudes are apparently well adapted to it. People have been in South America (debatable) about 15,000 years, so within that time humans have adapted. Similarly, the Inuit have some adaptions that allow them to better withstand the cold environment. Samoans have that reputation of being “large” due to a culture that encourages more eating - is that morphology genetic too, or simply cultural? Lighter skin has evolved in northern climates since humans departed Africa, so 70,000 to 35,000 years ago; and that skin melanin distinction has not significantly “re-evolved” for those American indigenous who settled in the tropics over the last 15,000 years. . So that brackets how fast that evolutionary trait might take to manifest.
True enough but firstly note that in terms of inherited disorders, 1) it’s already trivial to screen embryos for many disorders 2) the technology to correct single-point mutations in zygotes has been demonstrated and would be similarly trivial were it not for ethical concerns and 3) there are even gene therapies for adults now.
The point being: humans are changing our environment more quickly than our environment can change us. Much of that paragraph may be out of date within your lifetime.
It’s just not worth thinking about any of these things in terms of “evolution”, not biological evolution anyway.
And this is a good thing. Living with asthma is bad, dying of asthma is worse. For evolution to be working at optimal efficiency we would need to see a much higher mortality, with no particular “end” ever reached.
And consider how recent that observation has been generally acknowledged. And indeed there are still many in the US that think of “those people” as being inherently inferior and reproducing such as there is a “great replacement”.
The data has consistently said otherwise. And indeed in terms of IQ tests themselves, scores have been increasing, pretty much across the board. I’m not saying we’re evolving intelligence, just saying how wrong the notion of us getting much stupidz is.
I think this is not quite correct. It takes different smarts to be a hunter/gatherer vs. a farmer in an urban environment where you are constantly interacting with many, many other humans whose interests may not dovetail with your.
I think people forget that evolution isn’t about optimizing anything, it’s about what’s good enough to survive. Traits that don’t make significant different in reproduction for the most part don’t get eliminated. Mildly blurry eyesight, slight allergies, tendency toward Type II diabetes in middle age… none of these, even in hunter-gatherer societies, are likely to prevent reproduction or cause early death. They were never going to be eliminated. What’s happening is that our modern society and tech make detecting them and quantifying them easier, and in the case of late-onset problems, enabling people to live long enough to suffer from them as opposed to dying earlier from accidents and illness we can now avoid/prevent/treat.
We need to be careful to avoid confusing epigenetic effects from actual mutations to the genome. Epigenetic effects can reverse just as well. They are not evolution. They don’t lead to changes to the species. Rather they are just parameter settings that, within a range of bounds, can be passed on. Body size is one. How well a mother is fed can effect the size of her descendants. But only within bounds, and if the environment changes, and nutrition changes, the effect can reverse as the generations continue.
No, that’s just wrong. And irrelevant to evolution even if it were correct. I’d argue it doesn’t take smarts at all to hunt; every predator on the planet does it yet we don’t marvel at the intelligence of the house cat or spider. Hunting is mostly instinct; my 7 year-old daughters instinctively chase down butterflies and learn how to watch, approach, and catch them without me telling them anything. But when one of them brought home a sunflower sprout in a cup from school, the 3 of them combined didn’t have a clue how to take care of the plant.
We invented agriculture and have to teach it to each other to keep it going, same as written language. I’m not saying it takes much smarts to farm, but it’s not intuitive and takes a long-term attention to patterns and memory to figure out how it works and to do it right.
Right (agreeing with mike), the use of high intelligence to predate is one possible evolutionary niche, but there are plenty of predators that are not exceptionally intelligent, and vice versa. Elephants, pigs, raccoons, corvids, parrots are among the most intelligent animals.
The human evolutionary niche is not best described as either hunting or gathering or agriculture or anything else specific. What sets us apart is our ability to cooperate. We dominate the planet because we have an ability to work together to achieve our objectives that far exceeds any other species. And there are good arguments that our high intelligence evolved concomitantly with the complex social structures required for effective cooperation among non-kin. We are smart (at least in part) because we need to be able to “read” other people, to understand their motivations, to police cheating, and thus to form effective cooperative groups for mutual benefit. Whether hunting, farming or making the Hubble Space Telescope, human behavior has always been the apotheosis of cooperation.
I would still suggest that hunting, especially big game, requires more intelligence than planting food - particularly when the planting process has already been mapped out for generations. Hunting big game requires cooperation. Reacting to how prey behaves requires quicker thinking.
Of course, once society becomes dense enough (population-wise, not intelligence-wise) then more intelligence is called for to deal with the number of people around. Hence the trope of the dumb rural farmer vs. the smart city slicker, who has seen and learned more things and more tricks. But data about intelligence suggests it is as much “learned” (nurture) as it is genetics (nature). A lot of human behaviour falls in the category of cultural knowledge. Early tool-making humans seem to have learned and improved the flint-chipping craft of their elders - and most human knowledge is similar, building on what has gone before. It’s a form of evolution of knowledge, separate from genetics.
Yes, the question is - are we selecting for a trait - giving that trait a reproductive advantage? I.e. the biggest meanest type becomes the head honcho and has more children, then that is the type we are selecting for. Good nutrition in a mother leading to bigger children only affects the children, not the genes. It’s whether something about that bloodline assures more success that drives evolution - why are they better fed? Are parents better hunters than others, or better at finding the right roots and berries because of better eyesight? Size? Sense of smell? or is it just because they live in a fertile valley or the herds of buffalo extend as far as the eye can see?
The point of a concept like The Marching Morons is that modern society makes it easier for outlier cases to survive to reproduce. I recall reading about some Neanderthal grave which indicated the person had a congenital leg deformity but still appears to have survived to about 40 years old, which suggests this is not a new issue. We’ve just gotten much better at it.
The other issue with genetic treatments is whether they have a permanent effect on the gonads. Stem cells that replace the ability to generate white blood cells, or allow the generation of insulin, or fix Huntingdon’s but don’t affect the genes passed on are not changing evolution. A form of virus that invades the cells and edits the chromosomes, maybe so. Mitochondria would only help female offspring. etc.
But in general, evolution is change in response to environmental pressures. Instead, humans have changed their environment, removing more of the pressures which formed human evolution. Perhaps the information age and the deluge of data are creating alternative stresses.
If I had to point to some changes in human reproduction strategies - we’ve gone from a species that had a lot of children, and many died before reaching adulthood, to one where couples have few to none, but each child is more precious and given greater individual attention. (So physical resilience is less important) We’ve gone from a social organization where women often had little to no choice in reproduction, to one where they do. We’ve gone from a social organization of mainly permanent monogamy or polygamy to one of serial monogamy. I guess another question then becomes, to what extent do these new, different interpersonal requirements select for different genetic aptitudes?
