Is Modern Human Evolution Still Progressing or Have Selective Pressures Changed?

[MostlyHarmless]

I couldn't really find anything about this via Google, so I thought I'd pop on down to my favorite place in the interwebz!

So obviously evolution in early man was in an overall advantageous direction, but what about now, in modern man? Back then evolution in humans would have worked similarly as it does in nature as it does today, survival of the fittest. But now with social stigmas against discrimination in any aspect, along with technology, and our ability to more effectively "piggy-back" off one another, the effects of natural selection in humans would have to be very much diminished, right? (Aside from infertility and or other conditions that would render one incapable of reproducing). But, based on the conditions included in the sticky about evolution, we should still be evolving. On the whole, would that evolution still be progressive? Or would it be more of a side step?

 

[jfizzix]

Evolution only appears to trend from simpler forms to more complex forms because more complex organisms often happen to be more successful at reproducing, and propagating their genes.

In humanity, evolution still occurs just as much now as in centuries past. There are always factors affecting the likelihood that an individual will propagate their genes, and those genes make up the future gene pool. Civilization has given us a relatively comfortable lifestyle, so we are not as likely to die before physical maturity, but there's still the matter of sexual selection, where mating preferences drive who is more likely to mate.

 

[MostlyHarmless]

In humanity, evolution still occurs just as much now as in centuries past. There are always factors affecting the likelihood that an individual will propagate their genes, and those genes make up the future gene pool. Civilization has given us a relatively comfortable lifestyle, so we are not as likely to die before physical maturity, but there's still the matter of sexual selection, where mating preferences drive who is more likely to mate.

Ok then, we are now just seeing different factors that driving evolution?

You mention sexual selection, would this suggest that on the whole humans are getting more and more athletic, i.e. records always being broken? Since, in general the more athletic of us all tend to be held in a higher social light?

 

[jfizzix]

Humans on the whole would be getting more and more athletic only if more athletic humans tended to have more children than the average humans of the day. It is only that way that genes for athleticism generation after generation will become more prominent in the gene pool.

As a side point sexual selection is seen in other parts of the animal kingdom too. Peacocks have evolved their vibrant flashy tail feathers because over time peahens have preferred mating with flashier males, even though this makes the males more vulnerable to predators.

 

[thorium1010]

So obviously evolution in early man was in an overall advantageous direction, but what about now, in modern man? Back then evolution in humans would have worked similarly as it does in nature as it does today, survival of the fittest. But now with social stigmas against discrimination in any aspect, along with technology, and our ability to more effectively "piggy-back" off one another, the effects of natural selection in humans would have to be very much diminished, right? (Aside from infertility and or other conditions that would render one incapable of reproducing). But, based on the conditions included in the sticky about evolution, we should still be evolving. On the whole, would that evolution still be progressive? Or would it be more of a side step?

I am getting the impression that you are making evolution to be something which it is not. There is nothing called "progressive" in biology. Progressive is a political or a social term.
i think You are confusing evolution with modern day technological advancement(or drawing a similar analogy) which is a part of our society.evolution has no goal or destination, just as gravity does exist and it does what it does.

How do you know the effects of so called natural selection have diminished ? Just because we can treat a few diseases and overcome certain hurdles with technology, does not mean we have overcome natural selection.

 

[Pythagorean]

If natural selection were a landscape, I would agree that modern technology changes the shape of that landscape. However, measuring the effects as a single variable in which you can say its "more" or "less" of an effect seems a bit of a simplification.

 

[jackmell]

I couldn't really find anything about this via Google, so I thought I'd pop on down to my favorite place in the interwebz!

So obviously evolution in early man was in an overall advantageous direction, but what about now, in modern man? Back then evolution in humans would have worked similarly as it does in nature as it does today, survival of the fittest. But now with social stigmas against discrimination in any aspect, along with technology, and our ability to more effectively "piggy-back" off one another, the effects of natural selection in humans would have to be very much diminished, right? (Aside from infertility and or other conditions that would render one incapable of reproducing). But, based on the conditions included in the sticky about evolution, we should still be evolving. On the whole, would that evolution still be progressive? Or would it be more of a side step?

It's still evolution by selection based on adaptation to current environment. Take for example your discrimination comment. That IS the environment of today. And if a strong, healthy adult male, quite capable of surviving and getting all the women in a primitive society, were unable to "adapt" to that environment by discriminating sufficient harshly, his chance of survival and reproductive success would seriously diminish (be in jail) as opposed to a less strong male who nicely "adapted" to his current environment and followed the rules: the environment of "discrimination" selects those individuals which adapt. It doesn't have to be just natural.

 

[Andy Resnick]

<snip>So obviously evolution in early man was in an overall advantageous direction, but what about now, in modern man? <snip>

Interesting OP, although I would be careful about applying the concept of 'direction' (especially the idea of a single, goal-oriented, direction) with evolution.

Take eyeglasses- poor vision is undoubtedly a disadvantage, but a technological (dare I say cybernetic?) advance has neutralized the advantage of perfect vision.

Consider the modern (1st world) diet and the potential effects on our gut flora, which have co-evolved along with us host organisms. Has the transition from a 'paleolithic' diet to one of cooked, preserved, processed food impacted the genetic properties of gut flora?

Interesting question...

 

[lisab]

<snip>Back then evolution in humans would have worked similarly as it does in nature as it does today, survival of the fittest.<snip>

Back then, as now, selection was driven by who could reproduce the best -- and that's not the fittest, sometimes.

 

[Ygggdrasil]

Biological evolution at its core deals with how the frequencies of different alleles (gene variants) in a population change over time. The rate at which new alleles to become fixed in a population (i.e. for these alleles to outcompete all other versions of the gene), depends on the size of the population. Even alleles that provide strong fitness advantages will be fixed at slow rates in very large populations. Therefore, the large size of the human population (and the ease of mixing, so that no subpopulations can get isolated from the larger population) will make any significant changes to the human genome occur at an extremely slow rate.

Under what conditions might we expect human evolution to occur more quickly (relatively speaking since evolution occurs on geological time scales)? One situation would be a relatively strong selection pressure that strongly favors reproduction of individuals harboring specific traits. For example, worldwide pandemics could contribute such selection pressures.

Human evolution could also occur through genetic drift if some event drastically reduced the effective size of the human population. For example, if the population of Earth were to dramatically shrink (due for example to nuclear war, disease, asteroid strike), the allele frequencies of the population would change simply due to the bottleneck effect. Such a change would also make evolution through selection occur more readily as humanity repopulates.

Alternatively, a small effective population size could be achieved if a small group would become isolated from the larger population (i.e. the founder effect). A plausible example here might be a group that colonizes a different planet. Given enough time isolated from the population on Earth, such a group would eventually diverge enough from the earthbound humans to be recognized as a separate species.

Finally, I will note that technology could potentially affect human population genetics in the near term. While natural evolution occurs over long time scales, artificial selection can occur much more quickly. Technologies are already being developed that allow for preimplantation genetic screening of embryos, allowing parents to choose particular traits for their children. It is also plausible that technologies to enable the engineering of specific traits into embryos will be available within our lifetimes (we can already engineer embryos, but the technologies are not yet very efficient or safe, and in most cases we lack the knowledge of how to engineer most traits). The widespread adoption of such technologies could significantly change the composition of alleles in the human genome over a relatively short timescale.

 

[Borek]

Back then, as now, selection was driven by who could reproduce the best -- and that's not the fittest, sometimes.

Depends on how you define "the fittest". "Best fit to the task of reproduction" will work OK.

 

[jackmell]

. A plausible example here might be a group that colonizes a different planet. Given enough time isolated from the population on Earth, such a group would eventually diverge enough from the earthbound humans to be recognized as a separate species.

Another planet Ygggdrasil? Won't be H.sapiens when they get there. I'd have to look at the phylogenetic tree where invertebrates separate from veterbrates to classify the new humans at the end of that trip at which point they not only wouldn't be able to colonize the new planet but probably wouldn't want to since they would have grown so nicely accustomed and so well-adapted (without bones) to zero-gravity for so many generations. H.sapiens is forever married to earth.

 

[Ygggdrasil]

Another planet Ygggdrasil? Won't be H.sapiens when they get there. I'd have to look at the phylogenetic tree where invertebrates separate from veterbrates to classify the new humans at the end of that trip at which point they not only wouldn't be able to colonize the new planet but probably wouldn't want to since they would have grown so nicely accustomed and so well-adapted (without bones) to zero-gravity for so many generations. H.sapiens is forever married to earth.

I'm working under the assumption here that a civilization advanced enough to consider colonizing other worlds would have developed the technology to work out such problems (but if the trip to the new world is long enough, you could be right that the colonists could already be considered a separate species before they even arrive at the new planet). However, if populations on other planets were not reproductively isolated from the H. sapiens on Earth, you certainly could maintain hominid populations on different planets that would maintain their genetic identity as H. sapiens.

 

[MostlyHarmless]

That brings up an interesting point, what would it take for a group to branch off and become a different species? As I understand it, being of the same species means being able to interbreed and create a fertile offspring. How long would it take for two groups of humans to diverge enough to earn different species tags?

 

[Borek]

That brings up an interesting point, what would it take for a group to branch off and become a different species?

Isolation.

 

[jackmell]

That brings up an interesting point, what would it take for a group to branch off and become a different species? As I understand it, being of the same species means being able to interbreed and create a fertile offspring. How long would it take for two groups of humans to diverge enough to earn different species tags?

Life is non-linear and massively contingent (using Gould's term). Punctuated Equilibrium right. It depends how fast they change and how they change. What if we have another Cambrain Explosion? What about the Butterfly Effect? Could a very small, critical, fundamental mutation in an isolated population rise through the gene pool effectively blocking successful mating with other populations? What possible type of mutation to the human genome could cause such a block? Could a change to single protein, corresponding to a critical DNA base-pair mutation be sufficient?

Life is extremely non-linear, the smallest of change can cause the greatest effect. Based on this fact, I would answer yes to the last question. However the allele (genetic form) of that change would of course have to rise in frequency in the gene pool, i.e., be advantageous to survival or reproductive success more so than the unchanged form.

 

[MostlyHarmless]

Isolation.

That's what I thought, but are there not small groups of people all over the world that ARE isolated?

 

[Borek]

That's what I thought, but are there not small groups of people all over the world that ARE isolated?

Not for long enough.

 

[Evo]

Abnormalities can become the norm in small, isolated communities, such as with this tribe in Africa.

 

[edwardr]

David Attenborough was in the news recently claiming "human evolution has stopped." While the selective pressures and even the landscape for natural selection has changed drastically for humans in the post-agrarian and post-industrial world, there are still factors affecting human breeding, survival and success -- humans are certainly "still evolving."