Does sentience remove us from natural selection/evolution?

[Traab]

I was thinking about this awhile back and decided to bring it here out of curiosity. I know one of the fundamental aspects of darwin style evolution is survival of the fittest where to put it very basically, when a species develops a trait that makes it more likely to survive and thrive that trait gets passed on while those who lack said trait tend to die out before reproducing, eventually leaving only that dominant trait. As one random example, moths that have a better form of camouflage pattern are less likely to get eaten before reproducing, so more moths that look like them are born.

However, we humans arent really as strongly beholden to that idea anymore. We dont need to be a certain size to be more likely to survive, we dont need to be at least so fast or strong to get our food. Our immune system is less important because we have medicine now and the ability to care for ourselves even in the face of what would be a lethal defect living in the wild as an animal thus passing on the potential to future generations. It still does have an effect, but its greatly muted by the fact that we have advanced enough to alter our environment around us instead of altering ourselves to fit. As an example, we can live in environments that would be borderline lethal to us normally because we own air conditioners and space heaters among other ways to control our body temp relative to our surroundings. But in the end, our evolution as a species is no longer really connected to "survival of the fittest" as you no longer have to be the fittest to survive.

So what do you guys think?

[Chronos]

As long as some people have more descendants than others, and as long as the reasons for that disparity are at least partly heritable (note: not necessarily through genetics), natural selection will continue. Sentience does mean, however, that the sorts of evolutionary pressures we'll face will look completely different from what they used to.

[deuterio12]

I was thinking about this awhile back and decided to bring it here out of curiosity. I know one of the fundamental aspects of darwin style evolution is survival of the fittest where to put it very basically, when a species develops a trait that makes it more likely to survive and thrive that trait gets passed on while those who lack said trait tend to die out before reproducing, eventually leaving only that dominant trait. As one random example, moths that have a better form of camouflage pattern are less likely to get eaten before reproducing, so more moths that look like them are born.

However, we humans arent really as strongly beholden to that idea anymore. We dont need to be a certain size to be more likely to survive, we dont need to be at least so fast or strong to get our food. Our immune system is less important because we have medicine now and the ability to care for ourselves even in the face of what would be a lethal defect living in the wild as an animal thus passing on the potential to future generations. It still does have an effect, but its greatly muted by the fact that we have advanced enough to alter our environment around us instead of altering ourselves to fit. As an example, we can live in environments that would be borderline lethal to us normally because we own air conditioners and space heaters among other ways to control our body temp relative to our surroundings. But in the end, our evolution as a species is no longer really connected to "survival of the fittest" as you no longer have to be the fittest to survive.

So what do you guys think?

Brains and a sharp mind are just as effective as being strong/big/fast enough if not more. Other animals like crows and foxes also rely on cunning over simple raw power to survive, we just kinda hyper-specialized in it.

And good luck getting an human partner to reproduce if you can't pull some smarts.

Case in point, human babies have huge heads for their bodies. Our necks can't even lift our own own heads during our early life.

The only reason baby heads aren't getting even bigger is because then it would be plain impossible for the baby to get out of the mother (and women hips did get wider over time to try to allow for babies with bigger heads, but also hit a limit where any wider hips would make it harder to walk).

The immune system and medicine thing is a whole can of worms on its own since diseases evolve extremely fast, and modern medics actually try to hold back in using antibiotics as much as possible precisely to slow down the disease evolution. Peniciline for example was extremely effective back in the day, nowadays still good but you'll need bigger amounts for the same results because after decades of heavy peniciline use, the diseases are catching up, and so we need to keep being smart with medicine or things will get ugly.

[Traab]

As long as some people have more descendants than others, and as long as the reasons for that disparity are at least partly heritable (note: not necessarily through genetics), natural selection will continue. Sentience does mean, however, that the sorts of evolutionary pressures we'll face will look completely different from what they used to.

But my point is, natural selection is based around improving the species as generally speaking, and over time, positive traits survive and negative ones fade away through breeding and survival rates, but for humans that doesnt come into it nearly as strongly because we have so many methods for overcoming any negative traits that there is far less pressure from nature stopping them from being continually passed down. If a wolf is born without one of its limbs, its going to have a very hard life and probably die young. When a human is born minus a limb, we can provide alternatives that allow them to live a full and happy life. So that genetic trait of being born without a limb wont last very long for wolves but it will likely be passed down forever among humans because there is nothing stopping said human from succeeding in life, finding a mate, and pushing out a few sprogs. Please note that I have no idea if that specifically applies to missing limbs specifically, it was just an off the cuff example of something that would be a life and death issue in the wild but is fairly straightforward to deal with among humans.

[Razade]

I was thinking about this awhile back and decided to bring it here out of curiosity. I know one of the fundamental aspects of darwin style evolution is survival of the fittest where to put it very basically, when a species develops a trait that makes it more likely to survive and thrive that trait gets passed on while those who lack said trait tend to die out before reproducing, eventually leaving only that dominant trait. As one random example, moths that have a better form of camouflage pattern are less likely to get eaten before reproducing, so more moths that look like them are born.

That's not "Darwin Style" Evolution to start with, for one. For two, there's just...evolution. Traits based on via natural selection. It has nothing to do with "Survival of the Fittest" as has become a meme. Evolution selects against, not for, traits. If a trait (like the Laryngeal Nerve of a Giraffe) isn't actively detrimental to a species then it goes on. Evolution is plastic to its environment.

However, we humans arent really as strongly beholden to that idea anymore. We dont need to be a certain size to be more likely to survive, we dont need to be at least so fast or strong to get our food. Our immune system is less important because we have medicine now and the ability to care for ourselves even in the face of what would be a lethal defect living in the wild as an animal thus passing on the potential to future generations. It still does have an effect, but its greatly muted by the fact that we have advanced enough to alter our environment around us instead of altering ourselves to fit. As an example, we can live in environments that would be borderline lethal to us normally because we own air conditioners and space heaters among other ways to control our body temp relative to our surroundings. But in the end, our evolution as a species is no longer really connected to "survival of the fittest" as you no longer have to be the fittest to survive.

So what do you guys think?

Humans are as strongly beholden to evolution via natural selection now as we were when we crawled off the Ethiopian Savannah. We never had to be as strong as our food, we never were. We didn't have to be as fast as our food either. In fact, it was our tenacity and our ability to travel long distances at a constant speed that allowed us to hunt which then allowed us to get better access to protein which helped select for brain size and function which led to us making fire which led to more of that and...here we are. Humans were, and probably still are since in an evolutionary time scale we're not really that far removed from what we were when we first were designated "human" status, incredibly pursuit hunters. The best, by a lot of metrics. Combine that with tool use and that's how humans became the dominant species on the planet.

I think you're really counting humanity out. Humans lived in far far worse conditions before. We survived the Toba Incident and an Ice Age. We traveled across the entire world save for the very most extreme locations. Sure, modern man would have some growing pains going back to that style of life but again. We're the exact same species now as we were when by all metrics there was only as few as a thousand breeding pairs of our species.

So no. I don't think our sentience has removed us from natural selection or evolution. We are evolving even now.

But my point is, natural selection is based around improving the species as generally speaking, and over time, positive traits survive and negative ones fade away through breeding and survival rates, but for humans that doesnt come into it nearly as strongly because we have so many methods for overcoming any negative traits that there is far less pressure from nature stopping them from being continually passed down. If a wolf is born without one of its limbs, its going to have a very hard life and probably die young. When a human is born minus a limb, we can provide alternatives that allow them to live a full and happy life. So that genetic trait of being born without a limb wont last very long for wolves but it will likely be passed down forever among humans because there is nothing stopping said human from succeeding in life, finding a mate, and pushing out a few sprogs. Please note that I have no idea if that specifically applies to missing limbs specifically, it was just an off the cuff example of something that would be a life and death issue in the wild but is fairly straightforward to deal with among humans.

No. That's not really how evolution works. Again, evolution selects against and not for traits. A negative trait can remain so long as it doesn't directly impact the ability to breed. We don't have anywhere near the level of control over our biology to just straight up remove negative traits from the equation as you'd like to assert. Modern medicine isn't that great and neither is modern technology. The mutation of a missing limb isn't negative enough in the current condition to be selected against. Obviously. Or it wouldn't be present. We're talking about time scales that render congenital birth defects fairly meaningless here.

A great example is Sickle Cell Aenemia. On one range it's a terrible disease that has a truly negative impact on the person who has it. On the other range, we know that Sickle Cell provides some protection against malaria. Which is an even worse disease. The number of people in the first range as opposed to the second is low enough that Sickle Cell isn't just bred out of us as a species and the people who have it that survived malaira had kids with the possibility that it could be as bad as the first range. The benefit and the negative balanced out over all. Sickle Cell isn't a positive trait however and it still has issues for those who have some protection against malaria.

Also also, plenty of other animals are sentient. Pretty much every animal is sentient if you define it as having basal perception and feeling. We've done plenty of studies on plenty of mammals that indicate they have rudimentary levels of empathy, not just in their own species, and have emotions. Not the same as us, or in the same way, but emotions none the less. Not every animal is sapient. I'm not sure if there are any other animals but us that are sapient. Octopus and dolphins probably come close.

[sleepy hedgehog]

Rather than think of evolution as "survival of the fittest".
It's better to think of it as "death of the insufficiently fit"
If something survives, and reproduces, then by definition, it was sufficiently fit.

As long as you have variation, differential reproduction, and heredity, you will have evolution by natural selection.
(This applies animals, stories, memes and everything else that meets these requirements)

Only tangentially related but:
One could make the argument that the most fit land mammal of the world (excluding humans) are cows.
Because their flesh is tasty.
(If you measure by highest total mass.)
An odd niche? Sure. But effective none the less.

[Conradine]

In my opinion no.
But I think some primates have some kind of rudimentary sentience too.

[halfeye]

No.

So long as dying before you reproduce removes you from the pool of potential ancestors, natural selection applies to you. We might be getting close to the tipping point on that, but we're mostly not there yet.

Only tangentially related but:
One could make the argument that the most fit land mammal of the world (excluding humans) are cows.
Because their flesh is tasty.
(If you measure by highest total mass.)
An odd niche? Sure. But effective none the less.

Highest total mass? number of individuals, is surely a more plausible measure, in which case it's chickens by a huge number, or, including plants, wheat, or rice, followintg those potatoes or tomatoes, apples for number of fruit but the trees are big and carry a lot of fruit per tree per year.

[Lvl 2 Expert]

But my point is, natural selection is based around improving the species as generally speaking, and over time, positive traits survive and negative ones fade away through breeding and survival rates, but for humans that doesnt come into it nearly as strongly because we have so many methods for overcoming any negative traits that there is far less pressure from nature stopping them from being continually passed down. If a wolf is born without one of its limbs, its going to have a very hard life and probably die young. When a human is born minus a limb, we can provide alternatives that allow them to live a full and happy life. So that genetic trait of being born without a limb wont last very long for wolves but it will likely be passed down forever among humans because there is nothing stopping said human from succeeding in life, finding a mate, and pushing out a few sprogs. Please note that I have no idea if that specifically applies to missing limbs specifically, it was just an off the cuff example of something that would be a life and death issue in the wild but is fairly straightforward to deal with among humans.

Darwinian fitness basically means having lots of offspring in the long run. Evolution is a design process (of sorts) that results in organisms that keep reproducing under the changing circumstances on Earth. And those circumstances include those created by life itself. Whether that's other species or your own. The first oxygen producing lifeforms would probably still have been quite vulnerable to the chemically aggressive substance that is free molecular oxygen. They were creating the circumstances for their own selection. Humans do the same. We navigate an urban jungle now, but it's no less of a jungle. There are lots and lots of factors that correlate to how much children people have, and most of those factors have a genetic component. Think of social and emotional intelligence, the ability to read, write and calculate, all sort of abilities tied to gathering money, the mindset about what to do with that money. Spend on yourself and attract a higher quality mate? Save for your kids and give them better chances? Blow it on a party lifestyle possibly resulting in lots of children that never see their father? I'm not saying I know what the "right" choice is, especially since the circumstances keep changing on us, and what seems like a good Darwinian bet now could get thrown back in our face a few generations from now, but there's definitely selective pressure.

Okay, that's not entirely true. There is something else going on as well. And that is that selective pressure, while always present, is not constant in its intensity. In periods of relatively low pressure species' flourish. If there are less whalers, the number of whales goes back up. However, this does not mean evolution is slowing down. It just means selection is slowing down. Evolution after all is both mutation and selection. Periods of low selective pressure and large populations allow a population to diversify. Random mutations occur and spread through the population, where some of them will turn out useful during the next round of strong selective pressure. As far as I understand it, human diversity is currently low. It may not look like it now, but we went through quite a few bottlenecks during the last several hundreds of thousands (or millions, who's counting?) of years. Chimpanzees, as threatened as they currently are, show more diversity than humans do, because for them the same period has been relatively stable, up until recently. This effect goes double for anyone without semi-recent African heritage. Our big out of Africa moment was also a bottleneck, a time of hardship and loss of genetic material. To Complicate things further, selective pressure doesn't just result in the loss of genes that are (currently) bad or detrimental. A bottleneck like that results in the loss of a lot of genes that just are, that exist. For example: there are currently only a few thousand cheetah's left, and they're completely gone from over half their former range. Now try to imagine thinning out the world population of humans to several thousands or even several tens of thousands across half our current range. Even just the diversity you can see is going to go down drastically, never mind all the variant of genes that code for a protein that plays a role in the signal pathway that... Cheetah's in other words are on their last legs. They might pull through their current crisis, but change the circumstances to introduce another form of strong selective pressure and they simply lack the genetic diversity to adapt to their latest problem. They will need a period of rest and diversification, like humans are currently going through, to get back on their feet.

In short: selective pressure is not gone, it has changed, and it sits at a relatively low level. Neither of those things are bad for the species. Evolution is both mutation and selection.

And yes, I was imagining this post as more readable as well. I use too many big words and long sentences...

[NichG]

Within lifetime adaptation actually accelerates evolution, and it does so (somewhat paradoxically) by weakening the immediate effect of natural selection, so that the dominant selection effects are actually more the long-term costs and benefits rather than primarily driven by epistasis. This is called the Baldwin Effect, and while it wasn't originally proposed with intelligence in mind, it certainly applies there.

Basically, you can think of the fitness landscape of an organism's genome as a rough surface with some particular average slopes. The roughness comes from things which are interdependent on each-other and would need to be changed simultaneously to maintain optimal function. For example, if you hard-coded the frequency you should use to power the muscles in your legs while walking, changing the length of your legs, the mass of your torso, etc would require you to simultaneously change that frequency correctly or you'd be a less efficient or robust walker. So even if walking faster with shorter legs would be good, it might end up being slow to evolve with that kind of schema.

If the organism can learn to adjust its walking frequency during its lifespan based on how well things work or don't work, then that effectively smooths out that roughness while leaving broad slopes unaffected. In essence, by weakening parts of selection that generally make most kinds of changes harmful, it enables evolution to find fitness improvements that would otherwise be inaccessible or slow to exploit.

Basically, its not always the case that 'stronger selection = more evolution'. Weaker selection can actually accelerate evolution in some cases (e.g. if there's strong epistasis).

[Knaight]

First things first - natural selection and evolution are not the same thing, there are other major mechanisms. There's sexual selection, which is absolutely still a thing, and then there's genetic drift, which there's no getting rid of but which has a greater impact the smaller a population is. Humans being megafauna, it tends to hit us harder than more than a few insect species, let alone bacteria.

Second, natural selection still absolutely exists. Even putting aside how "we have modern medicine" involves ignoring large sections of the world where availability is not great and lots of people still die to tuberculosis and malaria all you need is there to be any genetic variability that affects the number of offspring you have, or even the number of offspring they have. If you have expensive medical problems the number of offspring you can support is reduced, and while not everyone wants enough to reach that cutoff from a statistical perspective there's still a group difference there. If you're really good looking (sexual selection) you're more likely to be able to have as many offspring as you want, which again has a population differential. If you're genetically inclined to live longer, your family line is more likely to have more generations alive simultaneously, which can lead to more support for the youngest generation and allow it to be bigger.

The idea that selection is against and not for traits is also a simplification. That tends to show up the strongest, because really deleterious mutations tend to burn themselves out fast (for humans this is probably largely buried in the miscarriage rate more than something high visibility), but fundamentally it's more a matter of how differential fitness among populations distinguished by the presence or absence of an allele leads to a shift in the size of said populations next generation, which repeats. This applies both to positive and negative traits, and both are significantly outnumbered by tiny, neutral mutations that don't really do much and are only subject to genetic drift.

[sktarq]

For as much as I agree with many of the above saying that the question doesn't really work on a conceptual level I'd say It doesn't really work even by its own logic. So I am going to take the "Darwinian evolution" thing as settled law for the purpose of this post and aim to show that even by that metric sentience has not removed humanity from such selection pressure.

well since we had sentience for at least 50K years if it was sentience that kicked us out of natural selection we would see changes from then...

and since it was sentience that allowed for animal domestication and high/super high human population densities and the associated disease boom (mostly zoogenic) through our often malnourished, high density, sewage infested populations....and we have strongly shown evolution in response to these zoo-genic diseases.

yeah....I'm going with no.

there is also the whole highly successful mutation that fails to turn off the milk processing protein when we are "weaned" and thus allowing us to digest dairy into adulthood...unless you don't have that mutated gene and are thus lactose intolerant. And that mutation is likely less than 10K years old...or about 25% the age of the cave paintings in France which I would put as pretty convincing evidence of "sentience" at even the most limiting.

or look at the genetic expansion of blue eyes....we are not sure why they have such an effect but they certainly seem to lead to more surviving grandchildren.

also even the advent of things like processed foods causing the diseases of affluence (like diabetes CHD etc) have arguably shown signs of already being adapted to as shown by lower levels of those responses in populations that have had longer exposures to that diet though these findings are harder to show over time and are still controversial last time I checked.

as for gross physical adaptations that is harder to prove in part because we are so malleable in physical form due to our environment. Sure not as much as say cannabis but significantly and that hides A LOT of genetic variability.

So sentience? Certainly Not
the Agricultural Revolution? I wouldn't think so but I see more of a point especially on the gross level vs biochemically
the Industrial Revolution? Kinda looks that way at first glance but probably just too new to be obvious


Honestly I'd say sentience has triggered a firestorm of high pressure high speed mutations driven by various things but by large part natural selection-on the ability to handle digestion, immunionolgy, and probably brain effects (genetic ability to support language better could well lead to a tribe with that driving off, out competing, or genociding those tribes that don't for example) . So I'd say it actually increased the effect not removed it.

[Traab]

Ok, thanks all for the responses. I even understood some of them!

[Blackhawk748]

To put it simply it changed the pressures not removed them. I mean, facial structures and hair amounts have changed and that partially has to do with people finding certain body types mroe attractive which increases their odds of having kids. Other animals gain traits like that too. I belive Fiddler Crabs have that issue.

[Razade]

First things first - natural selection and evolution are not the same thing, there are other major mechanisms. There's sexual selection, which is absolutely still a thing, and then there's genetic drift, which there's no getting rid of but which has a greater impact the smaller a population is. Humans being megafauna, it tends to hit us harder than more than a few insect species, let alone bacteria.

It's certainly a part of evolution. You're also going to have to give some citations demonstrating humans are megafauna. Nothing I've seen has ever suggested that and a quick google brings up absolutely nothing to support that claim.[/QUOTE]

[DeTess]

It's certainly a part of evolution. You're also going to have to give some citations demonstrating humans are megafauna. Nothing I've seen has ever suggested that and a quick google brings up absolutely nothing to support that claim.

According to wikipedia, the threshold for being megafauna is commonly set at either 40 kg or 1000kg, so by the previous definition humans would be, and by the latter they wouldn't. This website suggests that there are multiple size categories within megafauna, and humans definitely fall into the lighter ones. Yeah, this surprised me too.

[Knaight]

It's certainly a part of evolution. You're also going to have to give some citations demonstrating humans are megafauna. Nothing I've seen has ever suggested that and a quick google brings up absolutely nothing to support that claim.

Of course it's a part of evolution - nobody is suggesting otherwise. Using the two as interchangeable is incredibly sloppy though, as it involves ignoring other important mechanisms. The line between natural and sexual selection is a blurry thing in places, but genetic drift is a whole other mechanism that works in a whole other way that is really important to understanding population dynamics. It's especially important when looking at populations that have done things like go through tiny bottlenecks, or which have relatively few members.

As for humans being megafauna, definitions have been provided above - the cutoff varies a bit, the human average is generally in the vicinity with humans generally containing significant fractions above the higher ones. Regardless of which you use you still tend to see the important characteristics that drive genetic drift, of usually smaller population sizes. Humans today are running really high there, but despite that there's plenty of insect species with more members. Looking at a longer time scale (even just a few generations back for humans, which is nothing in evolutionary time) this becomes even more pronounced. Even if you discard cases like bacteria, where you get orders of magnitude more than the whole human population inside individual larger organisms you tend to see populations running a lot higher for small insects than large mammals. As selection processes don't scale with population size and drift is essentially dampened by population size (it's effectively a typical randomwalk process at O(sqrt(N)) ) this makes humans have megafauna like traits in terms of what drives evolution even if you use a definition that doesn't include them.

That said, selection processes are a more significant component now than, say, right after the Toba event. Nothing brings drift to the fore like a population bottleneck, and we're as far from that as we've ever been right now (albeit maybe not temporally, depending on what goes down in the near future).

[Chronos]

It's not necessarily about dying, nor is it as simple as reproducing or not reproducing. It's about how many descendants you have. Modern humans almost never die before living long enough to reproduce, and seldom don't reproduce for other reasons. But some still have more descendants than others.

To pick an extreme example, Wilt Chamberlain had something on the order of 10,000 sexual partners. I don't know how many of them were using birth control, but even by a conservative estimate, he probably has hundreds of children. That's a lot more than most of us will ever have. And other basketball stars have gotten close to his number. Thus, from an evolutionary point of view, being really good at basketball makes a human more fit. And at least some of the traits that make someone good at basketball are heritable. If this connection between basketball ability and fitness continues for thousands of years, then we would expect humans to evolve to be better at basketball.

[warmachine]

To me, who cares? Our ancestors long, long ago could not escape the brutality of survival, reproduction and natural selection but we can. We write our own purpose and our own laws now, wisely or not.

[DeTess]

To me, who cares? Our ancestors long, long ago could not escape the brutality of survival, reproduction and natural selection but we can.

Citation needed? :P

[NichG]

Citation needed? :P

The demographic transition and voluntary lower birth rate in more developed areas...

Other things in the history of life on Earth have also switched from a 'maximize expected number of offspring' dominated mode; you've got r type vs K type reproductive strategies, group selection and multicellularity, endosymbiosis, ...

[Tvtyrant]

No, selection processes are still there. We just see them in different areas.

Dominant alleles become more common over time, selecting for greater uniformity.

The delay in breeding means that people whose fertility declines early in life are removes from the gene pool, so there is a slow shift towards later menopause and fertility decline.

[LibraryOgre]

But my point is, natural selection is based around improving the species as generally speaking

emphasis added.

And that's the problem. Natural selection is not based around "improving a species", it is based around adapting the species to its environment. If you radically change the environment in a few decades (say, hyper-concentrating the population into small areas, but with significant possible input from other concentrations to avoid the difficulties caused by a small or closed gene pool), you have simply changed the environment to which the species is adapting.

The classic example is moths in England during the Industrial Revolution. Prior to industrialization, white moths had a significant advantage, as they concealed well against the white tree trunks. After a few years of pollution, though, dark moths began to predominate, as the tree trunks were darkened by soot. Both had existed in the population, but on either side of the event, one side or the other had a distinct advantage.

Humans taking themselves out of "nature" will begin to adapt themselves to a new environment, but what those adaptations will look like remains to be seen. Since our population is huge and fluid, you also have that any such adaptations will take a long time to really take hold... but that doesn't mean that adaptations won't be made through reproductive fitness.

[Unavenger]

So, "Survival of the Fittest" is a bit of a confusing way of putting it, but in this case "Survival" means "Reproduction" and "Fittest" means "Best suited to reproduce." That is, whoever is most likely to reproduce is most likely to reproduce. Tautological? Yes, but it's important to look at it that way.

Normally, when we think of someone who is "Fit" we... okay, let's ignore the possible meaning of "Attractive"... we consider someone who is strong, smart, capable, etcetera. But in evolutionary terms, it doesn't have to mean that. The fact that it's meant that for most of history and prehistory (well, no, it hasn't quite - see peacocks and sexual selection - but that's a little bit of a tangent) isn't a massive coincidence. The strong are likely to survive, and you have to be alive in order to reproduce (okay, yes, you can drop dead during your partner's gestation period and still arguably reproduce after you're dead, but you know what I mean). So in general, the strong, smart, and capable were the fit.

But with sapience (I assume you don't mean sentience - dogs are sentient) comes a new set of priorities. Humans have ethics which say that you can't just let someone die because they're disabled. This somewhat blurs the boundary between what we consider natural selection and artificial selection, so there's a fraction of an argument that it removes us from natural selection, but not really (a dedicated campaign of eugenics would remove us from natural selection. Allowing people who would have died out in the wild to survive, not so much). But this doesn't remove us from survival of the fittest. It just changes how to be fit. You no longer need to be strong. You don't need to be smart (some would say you actually have to be stupid enough to choose to reproduce or to do so accidentally, but let's not go too deep down that rabbit-hole).

The basics of evolution is that whatever traits make an entity (not necessarily a creature - and I'll get to that in a moment) likely to reproduce are more likely to be passed on because entities with those traits are more likely to reproduce. It doesn't matter what those traits are. If something that makes you less fit in the sense of less athletic, less intellectual, less capable, makes you more fit in the sense of more likely to reproduce, then the population will get less athletic, less intellectual, and less capable.

This is actually part of memetics - memes (not the internet ones - a meme is an idea, like an instruction, a religion or an understanding of a process) which survive well tend to survive for one of two reasons: one, they're actually worthwhile, or two, there's something about them which discourages people from stopping believing them (for example, being shamed for not believing them).

TL;DR:

We won't be removed from evolution, or indeed natural selection, so long as:

- We exist.
- We have some kind of heritable, variable traits.
- Some of those traits cause us to be "Fitter", meaning more likely to reproduce, than others would cause us to be.
- There is no worldwide program of eugenics forcing us into totally artificial selection.

[Grey_Wolf_c]

Humans taking themselves out of "nature" will begin to adapt themselves to a new environment, but what those adaptations will look like remains to be seen. Since our population is huge and fluid, you also have that any such adaptations will take a long time to really take hold... but that doesn't mean that adaptations won't be made through reproductive fitness.

I believe that there has been an example of rapid human adaptation making the rounds lately: female voice pitch has dropped significantly since the advent of talkies & workplace integration.

Grey Wolf

[Gnoman]

The demographic transition and voluntary lower birth rate in more developed areas...

There is strong evidence to suggest that the lower birth rate in developed areas is a natural, non-voluntary process which mirrors the behavior of many (but not all) animal species. Without touching on any specifics, there are many historical examples of the birthrate fluctuating wildly with development levels even in places where "have lots of children" is a cultural norm.

[Chronos]

I don't think it's correct to separate out "artificial selection" and "sexual selection" as being separate from "natural selection". Those are still selecting in response to the environment; it's just that we ourselves are also part of our environment.

[Tvtyrant]

I don't think it's correct to separate out "artificial selection" and "sexual selection" as being separate from "natural selection". Those are still selecting in response to the environment; it's just that we ourselves are also part of our environment.

Also the issue of chase away theory comes to mind. Sexual selection often gears itself towards absurd and impractical secondary sex characteristics which are only checked by them making individuals unfit in other ways. Oversized antlers and peacock tails are normal where predation doesn't interfere, and the issues with chase away in modern times is a major point of cultural contention right now.

[veti]

Highest total mass? number of individuals, is surely a more plausible measure, in which case it's chickens by a huge number, or, including plants, wheat, or rice, followintg those potatoes or tomatoes, apples for number of fruit but the trees are big and carry a lot of fruit per tree per year.

I'm guessing that the most numerous mammal is probably the brown rat. If you remove the "mammal" qualifier, then there are hundreds of insect species that beat all mammals easily, but the title would probably go to some kind of ant.

[halfeye]

I'm guessing that the most numerous mammal is probably the brown rat. If you remove the "mammal" qualifier, then there are hundreds of insect species that beat all mammals easily, but the title would probably go to some kind of ant.

Well I was thinking of tame species, but if we're not bothering about that, the most numerous is perhaps a bacterium, and of sexually reproducing species, probably a grass, though it might be a nematode, and among the mammals it's almost certainly a vole.