Why are some humans evolving faster than others?

[Moonbear]

None of this discussion has much to do with evolution, per se. Evolution in it's simplest explanation is change in a species over time. There is no provision for direction of change, for positive or negative, for superior or inferior, simpler or more complex, just change.

What the rest of this discussion is getting into is selection...natural selection, artificial selection (though evolutionary biologists would likely argue if this is a real thing and not just an extension of natural selection), sexual selection, etc. There is no such thing as "superior and inferior" in the selection process...something either confers fitness for survival and passing on one's genes, or reduces fitness making it harder to survive to pass on one's genes, or is neutral. There is a wide spectrum of heights which have no effect on one's ability to find a mate and pass on one's genes. The extremes on either end do affect ability to pass on one's genes...on the extremely short end, some forms of dwarfism would prevent one from passing on one's genes, at least if you are female, simply due to there not being enough space in the pelvic and abdominal region to safely carry a pregnancy to term, and on the extremely tall end, the endocrine disorders that lead to giantism would also hinder fertility. For the rest of the height spectrum, the tall couple who raises their countertops a couple inches to avoid sore backs while working in their kitchen have no less chance of having children than the short couple who keeps a step stool out at all times to reach the top shelves in the cabinets (or just doesn't use those shelves).

 

[tribdog]

The real reason humans have stopped evolving is because God died. either that or he made me and knew he had finally got it right.

 

[DaveC426913]

There is a wide spectrum of heights which have no effect on one's ability to find a mate and pass on one's genes. The extremes on either end do affect ability to pass on one's genes...on the extremely short end, some forms of dwarfism would prevent one from passing on one's genes, at least if you are female, simply due to there not being enough space in the pelvic and abdominal region to safely carry a pregnancy to term, and on the extremely tall end, the endocrine disorders that lead to giantism would also hinder fertility. For the rest of the height spectrum, the tall couple who raises their countertops a couple inches to avoid sore backs while working in their kitchen have no less chance of having children than the short couple who keeps a step stool out at all times to reach the top shelves in the cabinets (or just doesn't use those shelves).

Well, as you point out, one must find a mate in order to pass on ones genes. Physiologistics aside, only time and retrospect will determine if extremes in height will have been a sexual selection factor.

 

[Schrodinger's Dog]

Well, as you point out, one must find a mate in order to pass on ones genes. Physiologistics aside, only time and retrospect will determine if extremes in height will have been a sexual selection factor.

I've always found some real puzzles with this model. There kind of test cases. Whilst it's been determined for example that homosexuality at least has some sort of genetic component (see http://www.newscientist.com/channel/sex/dn9413-male-sexuality-may-be-decided-in-the-womb.html") but is not solely caused by genetics as far as we know. How does a gene or set of genes or a hormonal genetic effect that reduces the possibility of having children to almost 0, get passed on from generation to generation? And that's in humans. In animals it's obviously an even more strongly genetic component. What on Earth is the point of homosexuality? I mean no offence if you're gay at all? But why is it obviously not detrimental to the genome? Nature does not allow something to survive if it is detrimental to the number of offspring a species has, when it reduces it to practically zero, it is even more baffling?

 

[DaveC426913]

How does a gene or set of genes or a hormonal genetic effect that reduces the possibility of having children to almost 0, get passed on from generation to generation?

Perhaps as a form of genetic altruism i.e. it furthers the species rather than the individual.

In lab tests, overpopulations of rats produced an increase in this behaviour (IIRC, sorry, no citation). One could argue that it would help the species as a whole by lowering competition for mates.

As to how it gets passed, well one could hypothesize that groups deficient in this gene too easily wiped themselves out in mating competition, thus favouring populations that had the gene present. (So you see that, while the manifestation of the gene might limit offspring for the individual, the lineage that had that gene (including their childbearing siblings) would less likely be killed before bearing offspring.)

 

[Schrodinger's Dog]

Perhaps as a form of genetic altruism i.e. it furthers the species rather than the individual.

In lab tests, overpopulations of rats produced an increase in this behaviour (IIRC, sorry, no citation). One could argue that it would help the species as a whole by lowering competition for mates.

As to how it gets passed, well one could hypothesize that groups deficient in this gene too easily wiped themselves out in mating competition, thus favouring populations that had the gene present. (So you see that, while the manifestation of the gene might limit offspring for the individual, the lineage that had that gene (including their childbearing siblings) would less likely be killed before bearing offspring.)

Yeah cannibalism and homosexual activity in rats are behaviours that increase at high population levels, I've read the material, no link needed. Obviously there the advantage is pretty clear, over population and destruction of resources caused by it are obviously detrimental.

That said I only know of one study that suggests at least a partial mechanism, and that is the sisters of gay men, tend to have more offspring, which it is suggested makes the "genes" for being gay actually genes for attraction to men. I can link the article if you wish. But it's one of those puzzles that intrigues me about biology. I also read an article about 1 in 10 rams being gay? I'm sure there's an advantage there, but for the life of me I'm not sure exactly what it is?

Another thing is that human females are far more likely to be bisexual than men are. This seems to be completely pointless. Nice but pointless from an evolutionary perspective.

 

[DaveC426913]

Another thing is that human females are far more likely to be bisexual than men are. This seems to be completely pointless. Nice but pointless from an evolutionary perspective.

Not at all. The thing that females need from a partner are things that can be gotten from any partner who has the means and desire to protect them while they have offspring. Gender is not a factor in the partner after the offspring are conceived.

You can see the advantage to having the female's options open after her man-mate has been killed in a fight.

 

[Schrodinger's Dog]

Not at all. The thing that females need from a partner are things that can be gotten from any partner who has the means and desire to protect them while they have offspring. Gender is not a factor in the partner after the offspring are conceived.

You can see the advantage to having the female's options open after her man-mate has been killed in a fight.

Yeah actually that makes sense in a community where men would often die young, because of the dangers of hunting etc. Women would probably make up a larger percentage of the population.

 

[mgb_phys]

Humans in most western countries are unevolving.
Evolution doesn't aim for faster/better/stronger - it just aims to produce more offspring that reaching breeding age. In most western countries the more successful ( by the measure of that society) you are - the fewer children you are likely to have.

So we are actively trying to evolve away from rich/educated/succesfull !

 

[Schrodinger's Dog]

Thus the rise of chav culture.

 

[DaveC426913]

Humans in most western countries are unevolving.
Evolution doesn't aim for faster/better/stronger - it just aims to produce more offspring that reaching breeding age. In most western countries the more successful ( by the measure of that society) you are - the fewer children you are likely to have.

So we are actively trying to evolve away from rich/educated/succesfull !

Except that sheer number of offspring is no longer necessarily the best indicator of long-term success. While the rich/educated/successful may not be having more offspring, what offspring there are are increasingly more in control of the rest of the world.

This is an area where "natural" evolution gives way to social evolution.

 

[DaveC426913]

Humans in most western countries are unevolving.

BTW, there is no such thing as "unevolving" (I know you didn't mean it seriously, but it's a good chance to correct a common mistake).

Evolution is an arrow that points only forward. However, the drivers that push it forward may switch directions willy nilly.

Even if you force it artificially, say by selecting and breeding the weakest of a given crop, it is still forward evolution, you are just breeding for different traits.

 

[Schrodinger's Dog]

Except that sheer number of offspring is no longer necessarily the best indicator of long-term success. While the rich/educated/successful may not be having more offspring, what offspring there are are increasingly more in control of the rest of the world.

This is an area where "natural" evolution gives way to social evolution.

I think with the limited knowledge I have, it's far too difficult to put social evolution in terms of evolution in a single paragraph, I think you could quite easily write a book on it and still not come to any firm conclusions. As you say though just saying well educated people have less children is a tiny, tiny piece of the overall pie.

 

[mgb_phys]

social evolution

There is no such thing as 'social evolution' - all real evolution cares about is getting as many copies of a gene out there as possible.
That involves getting as many mates as possible, having as high a chance of possible of them becoming pregnant and then the maximum number of offspring surviving to reproductive age.

Biology does nothing that doesn't improve those odds.

 

[Moonbear]

How does a gene or set of genes or a hormonal genetic effect that reduces the possibility of having children to almost 0, get passed on from generation to generation?

Recessive genes are one, multiple allelic traits are another, and when you're talking about something like homosexuality, one can overcome their sexual preference and still have heterosexual interactions that result in offspring...indeed, this was likely even more common when society forced people to hide their sexuality.

 

[Schrodinger's Dog]

Recessive genes are one, multiple allelic traits are another, and when you're talking about something like homosexuality, one can overcome their sexual preference and still have heterosexual interactions that result in offspring...indeed, this was likely even more common when society forced people to hide their sexuality.

Are you one of those people that believes you can pray out the gay? Because frankly I don't think you can become straight any more than you can force yourself to be gay. You might have children, but again that is such a small minority of the gay population it is far from explaining its prevalence in the genome, in fact it's a cop out.

Are you trying to say that the world trying to force people to hide their sexuality, explains the fraternal birth order effect, if you are, I'd be all ears to how you can explain it? As far as I know in science homosexuality is still a mystery, it seems to have many factors that explain it, but I don't think societal pressure on it's own is in any way going to explain anything worthy of scientific interest. Perhaps once you've achieved this miracle with humans you can then go on to explain it in animals, and therefore get your Nobel prize in biology. Like I say I'm all ears to hear how this incredible breakthrough is going to happen based on your opinion.

If you read the article you would know that the fraternal birth order effect has been removed from any societal influence. So in fact what you are saying to me is that you never read the article and have a rather non scientific view, that comes from your own personal prejudices? Or not, I don't know but when I hear arguments like that it reminds me of people who just have no real understanding of the issues involved. Now I don't want to insult you, but could you in all honesty consider the evidence and put gayness down to societal pressure, in any way shape or form?

I'm not sure what you are trying to say here? Could you clarify?

 

[Moonbear]

Are you one of those people that believes you can pray out the gay? Because frankly I don't think you can become straight any more than you can force yourself to be gay. You might have children, but again that is such a small minority of the gay population it is far from explaining its prevalence in the genome, in fact it's a cop out.

I don't know how you possibly could have misread my post so badly as to come to that conclusion. Nobody "becomes straight," but that doesn't mean there aren't a lot of people who fake it really well for the sake of fitting in with a society that would otherwise reject them. Look at all the married with children politicians being caught in homosexual, extramarital relationships...they just have to go through the mechanics of the process enough times to have a kid while otherwise living with your opposite-sexed "roommate" who is nothing more than a friend to you. You also seem to have ENTIRELY overlooked the more important points, which were the first two in my list...recessive alleles and multiple allelic traits. If there is, for example, a recessive gene for homosexuality, and a heterozygous male, as a completely hypothetical example since we don't know what genes might be involved, either shows no effect of the gene, or if there is incomplete penetrance of the gene such that the heterozygous male is perhaps a more nurturing father than one who is homozygous for the "straight" allele, then there is even a chance there's a selection FOR that gene. More likely, it's a whole bunch of different genes, which means anyone of them can get passed along with little or no effect, and only when several of them wind up expressed in one individual do you have an effect on sexual preference.

 

[moe darklight]

There is no longer the survival pressure that there was before (at least not for the richer countries, where medicine is available for most)... diseases, defects, and disabilities that would prevent an animal from reproducing (poor eye-sight or hearing, a weak immune system, physical weakness, etc.) have next to no effect on our chances of reproducing.

Isn't this bound to change the way we evolve?

Humans in most western countries are unevolving.
Evolution doesn't aim for faster/better/stronger - it just aims to produce more offspring that reaching breeding age. In most western countries the more successful ( by the measure of that society) you are - the fewer children you are likely to have.

So we are actively trying to evolve away from rich/educated/succesfull !

have you seen the movie Idiocracy?

... then again, is the premise of that movie so unlikely? methinks Mike Judge is a prophet, not an artist

 

[mgb_phys]

have you seen the movie Idiocracy?

... then again, is the premise of that movie so unlikely? methinks Mike Judge is a prophet, not an artist

Thank you - I saw the last half of the movie in a motel and never knew what it was called.

 

[DaveC426913]

There is no such thing as 'social evolution'

It wasn't my intention to suggest that social evolution was functionally distinct from evolution, merely that we as social creatures recognize a subset of traits.

 

[Schrodinger's Dog]

I don't know how you possibly could have misread my post so badly as to come to that conclusion. Nobody "becomes straight," but that doesn't mean there aren't a lot of people who fake it really well for the sake of fitting in with a society that would otherwise reject them. Look at all the married with children politicians being caught in homosexual, extramarital relationships...they just have to go through the mechanics of the process enough times to have a kid while otherwise living with your opposite-sexed "roommate" who is nothing more than a friend to you. You also seem to have ENTIRELY overlooked the more important points, which were the first two in my list...recessive alleles and multiple allelic traits. If there is, for example, a recessive gene for homosexuality, and a heterozygous male, as a completely hypothetical example since we don't know what genes might be involved, either shows no effect of the gene, or if there is incomplete penetrance of the gene such that the heterozygous male is perhaps a more nurturing father than one who is homozygous for the "straight" allele, then there is even a chance there's a selection FOR that gene. More likely, it's a whole bunch of different genes, which means anyone of them can get passed along with little or no effect, and only when several of them wind up expressed in one individual do you have an effect on sexual preference.

If you set up a model with societal factors, homosexuality would be removed from the gene pool fairly rapidly. Thus my point. Even with a multitude of factors, given enough time they would be self terminating. And there doesn't seem to be any reason for these genes to exist in the first place. I'd be tempted to say that it's a bit of a coincidence that several favourable genes could all come together to produce homosexuality when there are millions of more viable models in the animal kingdom, which is why I tend to dismiss that idea.

Yes of course it's a whole lot of factors and apologies for missing your point, but it still doesn't really explain anything.

There was some suggestion that uncles may have a supportive roll on the families but this was ruled out by studies because it found gay uncles were no more likely to be good uncles than straight uncles.

I'm sure you know enough about the subject to see how deeply flawed your model is.

I don't think there is enough prevalence of heterosexuality amongst the gay population, either in history or today to explain it still existing because of the societal influences, it just doesn't make any sense. I mean you could of said bisexuality, helps to preserve the genes. You could of said they were an evolutionary throw back, that still has some success. After all homosexuality exists in most animals from fruit flies to the great apes. You could of said that woman who have gay siblings have more children, in other words that the genes are expressed on the sex chromosomes by both men and women, and by some quirk of fate they increase population fitness. I don't think they are too far fetched unlike the societal pressure hypothesis. Or the idea that randomly fit genes come together and create homosexuality. I think that's a bit of a lazy idea/cop out, what is important is to suggest why the model explains human sexuality in terms of evolution in humans.

I think the answer is partly genetics, and partly psychosocial. But most likely it would not happen without the genes being present. I suppose it remains to explain why they exist at all given evolution.

 

[tribdog]

Is there a species of mammals that doesn't show some homosexuality behaviors? It hasn't been breed out of any of them. I don't know for sure but I think there are also homosexual birds and fish and reptiles.

 

[Schrodinger's Dog]

Is there a species of mammals that doesn't show some homosexuality behaviors? It hasn't been breed out of any of them. I don't know for sure but I think there are also homosexual birds and fish and reptiles.

Yeah I think you'd be hard pressed to find an mammal in the animal kingdom that does not exhibit homosexual behaviour. As for lower orders I think most of them do too. I know flies do.

 

[DaveC426913]

If you set up a model with societal factors, homosexuality would be removed from the gene pool fairly rapidly. Thus my point. Even with a multitude of factors, given enough time they would be self terminating.

This is not necessarily true. It is an oversimplication of the process. It is not simply a matter of heteros having a hetero gene, which they pass to their offspring, and homosexuals having a homosexual gene, which is not passed to their offspring.

 

[Schrodinger's Dog]

This is not necessarily true. It is an oversimplication of the process. It is not simply a matter of heteros having a hetero gene, which they pass to their offspring, and homosexuals having a homosexual gene, which is not passed to their offspring.

I never said it was. I don't think without a genetic component it would be as common as it is though. Unless there was a societal reason for homosexuality. I think it's a combination of nature , and nurture.

So any theory would have to explain both why it exists at all genetically, if we say it has some sort of genetic component and why it is expressed. I don't think saying it's a coincidence or that it just so happens that when several factors come together you get someone who is more likely to be gay, I don't really think holistically that explains anything.

 

[tribdog]

They say everyone has at least one homosexual experience in their life. What's yours Schrodinger's dog?

 

[Schrodinger's Dog]

They say everyone has at least one homosexual experience in their life. What's yours Schrodinger's dog?

I kissed my brothers mate on the lips once, as a joke. I haven't done anything more than that though. Since one of my best friends is bisexual and one is gay, I probably would have by now, if I felt that way inclined. I wouldn't care if I had the sort of feelings that made me want to have sex with guys, I don't have any issues with it. But unfortunately I can't force myself to be other than how I was born and raised.

 

[tribdog]

Want to make out?

 

[DaveC426913]

I've never had one, but my best friend had me convinced for several decades that he had had one. When he finally told me he'd been pulling my leg, I nearly belted him.

 

[OmCheeto]

http://en.wikipedia.org/wiki/Idiocracy" is on tonight.

It took me 20 minutes to figure out what the movie was called because I couldn't remember Lukes name.

Anyways, I was freakin because I thought it was some kind of autobiographical dream.

everything seemed a bit too real.