Humanity 's future : evolution, stagnation or extinction?

General Academics Science, Technology and Medicine
1

Will humans look a lot different in 2 million years? A popular view is that we will become less muscular, less hairy and less toothy, but more cerebral and ocular, and start approximating the so-called Greys of sci-fi fame.

I don’t think so, though. I think our evolution is complete. Our genes on average are stagnating or weakening from generation to generation, and we will die out soon. Why do I think this? Because of how we are cheating natural selection.

If you look at the rules of evolution theory, we depend on natural selection to ensure a strong genotype. In plants and animals alike, natural selection is the culling machine that eliminates the unfit individuals, and their associated genomes. But when it comes to humanity, we have outsmarted many of the mechanisms of natural selection. For example, very little running is required in making a purchase from your local butcher, and your chances of ending up with a platefull of succulent lamb chops, whether you are an exceptional sprinter or a coach potato, are equal. Maybe we have finally arrived at the point where survival of the fittest has become survival of the wealthiest. Every year there are fewer and fewer means of cheating natural selection that cannot be bought.

This will be our downfall. The end, indeed, is near. I’m guessing no more than 1 or 2 million years.

The answer to human survival, of course is simple, but unthinkable: Get rid of hospitals and medication. Engage in war. Abandon all laws. Revert to anarchy. Every man for himself. Indulge the selfish gene!

Mintaka

2

I think not. It is only the last 100 - 200 years that we managed “to beat evolution” but this we did while running on a fossil fuel economy. Once that is gone it will not be as easy. Nuclear can supply the energy but we get a lot more from oil and coal, things like fertiliser. Without that there is no way that the current world population can be fed. Maybe you are right and it will be the survival of the wealthiest. I think we have thousands rather than millions of years left.

3

One needs to bear in mind that “fitness” is contextually determined. A person who is a faster runner, better hunter, more agile climber, etc., is no more “fit” to survive in today’s societal climate with all its modern conveniences than the committed couch potato. However, should a radical transformation in the environment occur, this will probably change.

It is also incorrect to say, “evolution is complete,” as if evolution had some or other goal or objective. It doesn’t. If an individual organism is maladapted to its environment, it will be selected against. As humans, we have learned to adjust our environment to be more favourable for us. We have also learned to manipulate the genetic code, but one must realise that these achievements can change the course of evolution, not somehow halt or negate it.

From the perspective of evolution, what matters is how many offspring an individual produces and how many of them survive to procreate further. In this regard, despite poverty and disease, poor countries (mostly African ones) have Western societies beaten cold because, except for the US, population growth figures are either stable or declining, whereas they are positive in underdeveloped countries.

Humanity’s biggest threat is posed by adaptive microorganisms – bacteria, viruses, parasites, various spores and prions. Self-extinction or an asteroid collision, while real possibilities, are far less likely to occur, at least to the extent that all of humanity will suddenly and catastrophically be eradicated.

Finally, doomsayers have been around for as long as humans have been conscious of their own existence. Oddly, none of their predictions concerning the end being nigh, whether specific or vague and general, has yet eventuated. The reason is not hard to see: as a whole, humanity has an amazing capacity to roll with all sorts of changes, pretty much irrespective of how traumatic they may be. Doomsaying is a symptom of people getting older and finding it difficult to accommodate the pace and extent of changes in the social fabric that they are witness to.

I think it would be premature to write us off just yet.

'Luthon64

4
However, should a radical transformation in the environment occur, this will probably change.

Thats exactly the idea behind my expectation of our imminent extinction, yes. Should we be surprised by trying environmental circumstances, I think we’ll be less likely to survive than our much more robust ancestors of a million years ago if put in a similar predicament. Like the panda, we are effectively loosing our adaptability.

It is also incorrect to say, “evolution is complete,” as if evolution had some or other goal or objective.

“Complete” meaning “shan’t advance any further”. No evolutionary goal or aim is implied.

Doomsaying is a symptom of people getting older

Not so. I’ve been at it since my early teens! :wink:

Mintaka

5
Doomsaying is a symptom of people getting older and finding it difficult to accommodate the pace and extent of changes in the social fabric that they are witness to.
Calling me a doomsayer and old to boot! :-\ May have a few miles on me but not old yet.

Nothing last forever, and mammalian species (on average) only 1 or 2 million years. We already have a million years or so behind us. Big brains only really helped us in the last 10 - 20 thousand years. That is nothing.

6

I don’t know what gave you that idea. If anything, we are far better equipped than ever to withstand environmental turmoil. Our success as a species is patently obvious. We can anticipate likely disasters and make provision for, or even evade them.

Again, I have no idea where you got that from, but it is plainly wrong. While evolution is slow (because it happens over generations and individuals don’t evolve), it won’t stop happening. If nothing else, genetic drift alone will ensure that. We humans are still in a competition for survival now, and that’s hardly going to change. What’s happened is that our focus has shifted from merely surviving to providing some meaning in our lives, which demonstrates how much more successful at the game we are than most other species.

And it is your contention that, at some point, we will be faced with a disaster so huge and unforeseen that most if not all of humanity will disappear? If so, it is in any case an unprovable contention because every adversity that we do manage to overcome can be sidelined with a simple, “Well, that wasn’t it.” Remember also that you are extrapolating from the past – always a tricky thing to do in an essentially chaotic dynamical system (summary) – but the past has never before seen a species with anywhere near the degree of control over its own destiny that we both have and keep improving. Moreover, of all the sentient organisms on the planet, humans (by sheer number alone) are most likely to weather any major catastrophe. That is not to say, as mentioned earlier, that we won’t fall prey in huge numbers to some non-sentient, plague-like superbug. Again, though, there will be a few individuals who will survive such an onslaught because they are fortunate enough to have a genetic makeup that affords them increased resistance. They will go on to become the root stock of a new human genetic variant.

Don’t write us off yet. Our adaptability is amazing.

'Luthon64

7
If anything, we are far better equipped than ever to withstand environmental turmoil.

Equipped, yes. But what if we are divorced over a short period from our precious equipment (houses, sewage systems, supermarkets, hospitals and antibiotics). Say that energy crisis as mentioned by Tweefo strikes. All our toys become unplugged. We will find ourselves naked in the bush, and with very soft footsoles.

If nothing else, genetic drift alone will ensure that.
Genetic drift is not evolution. Genetic drift is random and will not help the species adapt on its own. Without natural selection, there can be no adaptation, and therefore no evolution.
We humans are still in a competition for survival now, and that's hardly going to change.

But we hardly have to claw each other’s eyes out fighting over food, we can have as many offspring as the government can support, and have medication available that was unheard of 100 years ago. Other species trying to share our niche? We simply call them vermin and blow 'em away with assorted caliber rifles and poisons. No competing animal can make a dent in our population. So unless you are referring to occasional and insignificant war and crime casualties, how exactly are we in competition for survival?

8

Perhaps you haven’t noticed it, but much of humanity is divorced from many of these conveniences, and still manages to do considerably better than most other organisms.

What fraction of the world’s human population depends critically on these toys and the energy that drives them? Are humans not engaged in intensive endeavours to address just this possibility as we speak? But in such a situation people will undoubtedly have a difficult time of it. Nobody is challenging that, but the intrinsic hardness of our soles hasn’t changed much since we left our caves. There hasn’t been sufficient time for evolution to accomplish such a thing. The point you seem to keep missing is that humans have evolved enormous adaptability for a wide array of different scenarios. Our adaptability is itself a product of evolution. To say that a few thousand years of civilisation are sufficient to negate that heritable characteristic is simply not correct.

Not on its own, no. But if you think it is irrelevant then you need to inform yourself more carefully. Genetic drift is a major source of genetic diversity, which diversity itself is a cornerstone of evolution.

I assume you mean to imply that we have (largely) done away with natural selection when it comes to ourselves. But have we? No, because all we’ve actually managed to do is to manipulate our environment to be more suitable for us. That doesn’t negate natural selection at all. We can’t just escape the laws of nature, only use them to our advantage. Human foetuses are spontaneously aborted in large numbers through miscarriages for reasons that are not well understood. There’s a good chance that this has a genetic component, perhaps an intolerance certain mothers have for certain things. Those foetuses have been selected against, while the ones that are born alive have a much greater chance of spreading their genes. Many children and adults die daily the world over from a wide range of diseases and medical conditions. Those with greater resistance and/or recuperative capacity are favoured, even in the presence of best medical practices. Technology hasn’t done away with natural selection. It has helped to bring about a dramatic increase in the viability of certain genetic compositions that would have been selected against in earlier times, adding to humanity’s genetic diversity. The human genome is much the same as it was a few thousand years ago.

True, but there’s hugely more to evolution than just that.

By fighting diseases. By competing for many different resources. By constant vigilance for new threats to our existence. By competing for mates. By protecting our children. I’m sure you can think of a few more. Once again: Just because the means and methods have changed by which we accomplish certain things, that doesn’t simply remove the underlying governing principles at a stroke.

'Luthon64

9
Perhaps you haven’t noticed it, but much of humanity is divorced from many of these conveniences, and still manages to do considerably better than most other organisms.
I've noticed, but don't think it is such a stretch of the imagination to consider the entire globe as a first world planet in the next 1,000 to 2,000 years. We may not be there yet, but it does appear that we are relying more and more on our clever inventions for survival, even though the ability to conceive such inventions is in itself an evolutionary product, as you rightly said. So I was really considering those (future) human populations that became depended on their inventions over some time (millenia), not those that never had any.
What fraction of the world's human population depends critically on these toys and the energy that drives them?
Again, I'm not speculating about the present situation. Total reliance on gadgets may take a few thousand years.
The point you seem to keep missing is that humans have evolved enormous adaptability for a wide array of different scenarios.
Point taken and noted, even agreed with. But the fact remains, this singular ability of ours to make our environment adapt to our whims was forged [i]in the bush under extreme conditions [/i], where one would pay with one's life for a minor miscalculation. In the first world globe, the penalties associated with cock-ups won't be nearly as severe. Natural selection will be rather diluted. End of human evolution.
Genetic drift is a major source of genetic diversity
Not disputing this either. Genetic drift is possibly essential to evolution. But without natural selection, whether genetic drift happens or not would be academic. The question is whether natural selection is decreasing or not.
... all we've actually managed to do is to manipulate our environment to be more suitable for us. That doesn’t negate natural selection at all.
But of course it does! Didn't you follow my butchery example? We have used our ingenuity to come up with sheep farming and butcheries, and therefore we don't have to catch our prey any more and therefore we have [i]relieved[/i] the environmental pressure that would select for fast runners and therefore we have negated natural selection for fast runners.
It has helped to bring about a dramatic increase in the viability of certain genetic compositions that would have been selected against in earlier times, adding to humanity's genetic diversity.
and then
The human genome is much the same as it was a few thousand years ago.
Seems to contradict. Not sure what you mean here.

Mintaka

10

All of the above citations indicate that you’re still somehow missing the basic point. If these are the gist of your extinction/stagnation argument (as I suspect they might be), then I’m afraid you have a naïve black-and-white view of what evolution is. How does our ability to help others survive adverse conditions that would probably have spelled their demise in the past in any way “dilute” natural selection? Because in your view it is somehow not “natural,” maybe? What, then, are the criteria that separate “natural” selection from “non-natural” selection? Whatever forms selection may take, they are all still subject to natural laws, so it is hard to see exactly what the distinction is that you’re driving at.

In the very first sentence of my first post in this thread I pointed out that “fitness” is contextually determined. This means that “fitness” is not gauged without reference to prevailing environmental conditions. Lions do well in African savannahs but probably won’t survive in the Arctic. Our ability to manipulate our environment affects how selection, natural or whatever you think the alternative is, plays out. It hardly eliminates it as a factor. If you think otherwise then I’m afraid your understanding of evolution is quite poor, especially in view of the examples I gave earlier of the kinds of selection pressures humanity is facing.

If, on the other hand, you mean to say that, because our mode of living is far more sophisticated than in days gone by, it is less robust and more susceptible to (radical) disruption by other factors, then even if that view is valid (and there are reasons given earlier to be suspicious), that has little to do with human evolution per se in a similar way to how a flash flood has little to do with the evolution of birds: their environment may be affected and some of them may not survive the change, but those who do will be on the whole incrementally better able to withstand the next one. That scenario is in any case patently not one of any genetic stagnation.

ETA: And lest we forget, most animals manipulate their environments as well, albeit in a more limited and less consequent fashion: they build habitats, they herd and form communities, they form symbiotic relationships, and so on.

That’s not true. The vast preponderance of our capability effectively to manipulate our environment was developed in the 20th century, tracing a long line back to the earliest tribal agrarian social arrangements, themselves no doubt derived from an evolutionarily advantageous herding impulse. In other words, our ability to adapt our environment is the product of a long and tortuous (and ongoing!) developmental evolution that became really effective well after humans were subject to any extreme conditions in the bush. To say it “was forged in the bush under extreme conditions” is totally to ignore its history.

There’s no contradiction. The human genome is much the same as it was a few thousand years ago but there is perhaps more diversity in it. An analogy would be a large class’ exam results: the average mark is still the same as in previous years but the spread of marks is wider, i.e. there are both proportionately more low and proportionately more high marks.

'Luthon64

11
I’m afraid you have a naïve black-and-white view of what evolution is.

Well, possibly, but unless Chucky’s big idea has been fundamentally revised since OoS, I shall continue believing that Natural selection is the singlemost important driver of evolution.

What, then, are the criteria that separate “natural” selection from “non-natural” selection?

I’ve never heard of “non-natural” selection before, but I suppose you could call any altruistic act that doesn’t benefit the survival of your own genes, “non-natural” selection.

In the very first sentence of my first post in this thread I pointed out that “fitness” is contextually determined.

Ok maybe we won’t necesarily die out due to our anthropogenic environment, but I still think our human evolution would just about grind to a halt.

The vast preponderance of our capability effectively to manipulate our environment was developed in the 20th century

Only because we were genetically able to develop this capability. Millenia of evolution brought us to the point where we could construct a wheel and a Hubble space telescope. If you plucked Leonardo da Vinci from the Renaissance and put him in the 20th century, he would surely be able to grasp the modern engineering feats. We hardly evolved into city building disease fighting, industrial giants in the space of 100 years.

But if you don’t mind, lets just clean things up a bit. All I’m saying is this.

  1. Humanity is rapidly changing its environment to minimize survival challenges.
  2. But natural selection depends on survival challenges.
  3. And evolution depends on natural selection.
  4. So human evolution will wind down or stagnate genetically.

Now as I understand it you disagree as follows:

with 3, because there is some other means of driving evolution.
with 4. because of genetic drift.

Correct?

Mintaka

12

And well you should because, together with genetic diversity, it is just that. However, it is the character of natural selection that you seem to have a very narrow view of and that we are debating.

Biologists have actually taken to speaking of “selection,” dropping the “natural” because it distinguishes “artificial selection” and also certain subclasses of natural selection such as “sexual selection, ecological selection, stabilizing selection, disruptive selection and directional selection.”

But you haven’t given a single good reason for this, nor proposed any mechanism(s) that would cause human evolution to “grind to a halt.” Your scenario is in any case implausible because as long as there’s even just a potential for genetic variation, evolution will continue owing to inevitable fitness differentials. It seems to me that you have this wrongheaded idea that natural selection hinges critically on predation of one form or another, or some derivative of it, like “kill or be killed.” The Wikipedia article on natural selection doesn’t even mention predation, and the word “predator” occurs only once in a figure caption that illustrates how sexual selection can override other apparently more obvious fitness criteria such as being able to move swiftly or having good camouflage.

No, I disagree with your points 2 and 4, as would any biologist. Evolution is not so much about whether you die or don’t die as it is about how many reproducing offspring you leave. Intrinsic individual survival is actually a quite small part of it (except of course for those individual organisms that die before reproducing at all), as the linked-to Wikipedia article makes abundantly clear. If you father a hundred children and die in an accident at the age of twenty in a car accident because you have slow reactions then you are evolutionarily more successful than the seventy-year-old ex-ping-pong-champion who produced two children in his life. If, statistically, people with slow reactions produce more children, then the slow-reaction genes will inevitably come to dominate after some generations. Similarly, if an individual is born with a mutation that couples increased pheromone production to high fertility and a healthy libido, chances are good that those genes will spread. Genetic drift may throw up one or other such evolutionarily successful combination at any time, and that is why human evolution cannot legitimately be said to stagnate or to have come to a halt.

'Luthon64

13

A very interesting discussion, although it has been a long time since I thought that humans stopped evolving - most notably since I looked carefully at the meaning of the word “natural” in natural selection (which has nothing to do with nature, it is the antithesis of artificial selection and should be viewed that way). I was immediately reminded of this discussion this morning when I read this article on natural selection affecting the human race. This study is, at this point, unpublished so the peer review is yet to be done (keep an eye on PNAS, it might be out this year, and we fortunate South Africans can access the journal for free).

The article makes a pretty strong case and will at least revive the debate amongst Evolutionary Biologists to the point where there are more studies and less circular debate.

James