Random Question About Genetic Traits
 

I was reading the thread entitled "How can gayness have a genetic basis?" and it got me to thinking...

Are there "cases" of genetic traits that are not desirable for reproduction that pass on anyway, and with "reason" (or perhaps I should say non-randomness)?

Let's call it a "Martyr Gene". A tribe needs a martyr to survive, but the martyr would not live long enough to reproduce. Naturally, he wouldn't pass on the gene.

HOWEVER, if instead his mother had a gene that said, "If I have a baby, there is a 1/100 chance he will be a martyr", then that mother's tribe will have a greater chance of surviving, assuming of course the martyr is able to sacrifice himself in a way that is beneficial to the society.

I'm not trying to make a point with this. Maybe it's an extremely elementary question, and if it is, I apologize, but I would really appreciate it if someone could indulge me and link me to a study or two.

Re: Random Question About Genetic Traits
 

By not desirable do you mean harmful to reproductive success, or just not helpful?

A trait does not have to make its host more fit, it just has to be fit within its host. A trait that actively makes its host less fit has a hard time.

As for your martyr scenario, I do not believe selection can occur in that fashion. Genetic traits that are helpful to societal productivity exist because they also directly help the carrier. In a society that has a certain concentration of cooperative individuals your survival and reproductive success is helped by also being cooperative. Someone here once posted a really old Dawkins video where he was using the selfish gene and the prisoners dilemma to demonstrate this elegantly.

Re: Random Question About Genetic Traits
 

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By not desirable do you mean harmful to reproductive success, or just not helpful?

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Harmful to reproductive success. Specifically his own. He could be helpful to the reproductive success of others.

Re: Random Question About Genetic Traits
 

It doesn't need to be rare - ant workers are infertile. Rare example are probably rarer as its harder to evolve, but its consistant with darwinism.

chez

Re: Random Question About Genetic Traits
 

Im fairly sure this is described to some extent in The Blind Watchmaker.

Re: Random Question About Genetic Traits
 

There stuff like Sickie-cell disease where inheriting the allele from both parents results in sickie-cell disease, but inheriting from just one parent gives increased protection from malaria.

Re: Random Question About Genetic Traits
 

Genes can reproduce in a way other than procreation -- by helping a related individual to procreate.

In a tiny group on the plains of Africa, the individuals will be closely related. A trait that might kill one individual, but help the group to survive, can be selected for.

Dawkins' _The Selfish Gene_ addresses this.

Re: Random Question About Genetic Traits
 

Kin Selection

Along Bill's line, there are plenty of examples of inbred colonies of animals that have self-sacrificing individuals (often in defense of the nest for example). You have to be careful not to extrapolate it to a larger level (species, etc.) because they must be closely related for this to work genetically.

Also, it's pretty complex neutral traits can get passed on regularly and negative traits can get passed on because they have a positive effect in other gene combinations, individuals, or situations (brought up in the gay threads). Also, including eusociality, sometimes it seems like a trait is really negative but actually has a positive effect (sexual cannibalism in mantids and some spiders for example)

Re: Random Question About Genetic Traits
 

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Are there "cases" of genetic traits that are not desirable for reproduction that pass on anyway, and with "reason" (or perhaps I should say non-randomness)?

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Yes.

Re: Random Question About Genetic Traits
 

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It doesn't need to be rare - ant workers are infertile.

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Exactly.

Re: Random Question About Genetic Traits
 

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By not desirable do you mean harmful to reproductive success, or just not helpful?

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Harmful to reproductive success. Specifically his own. He could be helpful to the reproductive success of others.

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If those others are his relatives than this could work if, in your martyr example, his sacrifice would result in them having enough kids.

Re: Random Question About Genetic Traits
 

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Let's call it a "Martyr Gene". A tribe needs a martyr to survive, but the martyr would not live long enough to reproduce. Naturally, he wouldn't pass on the gene.


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Yes there are. The kind of thing you are talking about is called "altruism." The gene may not be passed by this carrier, but this sort of gene would be a double recessive, so that this individual's brother or sister, possibly having one copy, will pass that copy along.

Some lethal genes are not selected-for themselves, but get passed along in "piggyback" fashion. That is, they are located near a selected-for gene on the chromosome. When crossing over occurs, genes clumped together, get crossed together.

Sickle-cell genes are highly selected-for in populations where malaria is prevalent, even though having two of them is fatal. So having a single gene for sickle cell anemia is common to about 50% of those populations. That's a balanced polymorphism.

Gayness, for want of a better word, has selective advantages because we used to be a family-oriented culture. That is, we are social primates organized into family groups. The purpose of biological life is production and reproduction: staying alive and passing on your genes. To keep offspring alive long enough to reproduce themselves and pass on those genes, it makes reproductive sense to have as many resources as possible - protection, food, and so forth. Because siblings share genes, a non-reproducing ("gay") member of the family group, provides more protection for the young and can acquire more food resources. That member's genes reside in the offspring also.

Ejecting gay persons from our families and communities is counter to reproductive success for the population as a whole.

Re: Random Question About Genetic Traits
 

Awesome. Thanks for the answers everyone.

Re: Random Question About Genetic Traits
 

Sorry to thread-jump, but...

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Sickle-cell genes are highly selected-for in populations where malaria is prevalent, even though having two of them is fatal. So having a single gene for sickle cell anemia is common to about 50% of those populations. That's a balanced polymorphism.

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It is, yes, 1 gene = fitter (and reproductive) 2 genes = quite unfit (though presumably even more resistant to malaria [img]/images/graemlins/wink.gif[/img] ) and less likely to reproduce. I cannot see how from there you get:

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Gayness, for want of a better word, has selective advantages because we used to be a family-oriented culture. That is, we are social primates organized into family groups. The purpose of biological life is production and reproduction: staying alive and passing on your genes. To keep offspring alive long enough to reproduce themselves and pass on those genes, it makes reproductive sense to have as many resources as possible - protection, food, and so forth. Because siblings share genes, a non-reproducing ("gay") member of the family group, provides more protection for the young and can acquire more food resources. That member's genes reside in the offspring also.

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What is this - eusociality in early human primates? Sure, I understand the notion of kin selection, but time and again various eminently plausible ideas run into the problem that a gene which causes its bearer to be less likely to reproduce must have a profound effect on the probability of its kin to survive in order for this 'back-door selection' to occur. Where are you getting this? I mean it's a nice theory, I suppose it could be true - I just don't see it. It appears as though you've started with the idea that gayness must be reproductively fit (not unreasonable) but that leads you, as soon as you see a plausible evolutionary niche for it, to proclaim this as established fact. Is there some documented evidence that gay people are better at looking after kids? That people feel a sense of primal 'rightness' (similar to that say of catching a fish, gutting and cooking it yourself) when they leave their children in the care of a gay relative? Such a feeling would not be real evidence of any particular kind - but it is what I would expect to find if what you say is the complete truth or even a sketch of it.

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Ejecting gay persons from our families and communities is counter to reproductive success for the population as a whole.

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Not anymore, by your own lights. I say ejecting gay persons from our families and communities is morally repugnant on the grounds of human liberty.

Re: Random Question About Genetic Traits
 

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What is this - eusociality in early human primates? Sure, I understand the notion of kin selection, but time and again various eminently plausible ideas run into the problem that a gene which causes its bearer to be less likely to reproduce must have a profound effect on the probability of its kin to survive in order for this 'back-door selection' to occur.

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Living in human society has skewed your vision of what happens in the natural world. The majority of organisms born don't reproduce, huge amounts die between the fertilized egg -> reproductive egg stage. Since most animals don't live to reproduce the loss of one who loses all possibility only costs a fraction of what you might think, thus the beneficial effect doesn't have to be profound at all.

Re: Random Question About Genetic Traits
 

I don't see this reflected in apes. Ants, yes. Vertebrates tend to invest far more in one batch or litter (to varying degrees) - primates more than most vetebrates, and humans more than any other primate. The beneficial effect of any gene tending against its bearer reproducing must, I think, be of a corresponding degree - not shown.

Now I realise that it may be true that, say, the majority of male apes do not reproduce. Do we then see that such apes as are observed to practice something like homosexuality (can't remember which specific ones, something like 'Barber apes' but I can't quite remember it)are given responsibility for the care of the group's young? And is this role assigned to gays of both genders?

It seems more plausible to me that if there was a pressure exerted in favour of gayness, the (male) gays would far more likely be hunters or soldiers. I can see how this kind of primitive labour division might result in fewer orphaned offspring, which might in turn mean less waste... but it's difficult to model this kind of waste-avoidance as directly beneficial without resorting to group-selectionism.

Re: Random Question About Genetic Traits
 

Do you mean bonobo chimps?

Re: Random Question About Genetic Traits
 

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Gayness, for want of a better word, has selective advantages because we used to be a family-oriented culture. That is, we are social primates organized into family groups. The purpose of biological life is production and reproduction: staying alive and passing on your genes. To keep offspring alive long enough to reproduce themselves and pass on those genes, it makes reproductive sense to have as many resources as possible - protection, food, and so forth. Because siblings share genes, a non-reproducing ("gay") member of the family group, provides more protection for the young and can acquire more food resources. That member's genes reside in the offspring also.

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What is this - eusociality in early human primates? Sure, I understand the notion of kin selection, but time and again various eminently plausible ideas run into the problem that a gene which causes its bearer to be less likely to reproduce must have a profound effect on the probability of its kin to survive in order for this 'back-door selection' to occur. Where are you getting this?

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Well, I "got" it from years of studying paleoanthropology in college and teaching genetics and evolutionary theory. Where do your ideas come from?

In order to make sense of altruism, we have to understand that it doesn't matter which of the examples of a specific gene survives, as long as it does. The source, which relative passes it on, becomes a matter of indifference. Once genes are deposited in the next generation, protecting that container, the individual with the genes inside, becomes the greatest driving force in behavior as long as production is constant. We don't think of the genome and how it evolves in terms of individuals, but in terms of populations. One of the most positive forces for selective fitness, is controlling the number of individuals in the population because production and reproduction are so intertwined as to be almost indistinguishable from one another.

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Ejecting gay persons from our families and communities is counter to reproductive success for the population as a whole.

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Not anymore, by your own lights.

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I have no idea what this means.

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I say ejecting gay persons from our families and communities is morally repugnant on the grounds of human liberty.

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I agree and say the same thing. But that isn't the topic of the thread.

Re: Random Question About Genetic Traits
 

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Living in human society has skewed your vision of what happens in the natural world. The majority of organisms born don't reproduce, huge amounts die between the fertilized egg -> reproductive egg stage. Since most animals don't live to reproduce the loss of one who loses all possibility only costs a fraction of what you might think, thus the beneficial effect doesn't have to be profound at all.

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Exactly! Great post.

Re: Random Question About Genetic Traits
 

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Do you mean bonobo chimps?

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Pretty sure I do - cheers.

Re: Random Question About Genetic Traits
 

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Well, I "got" it from years of studying paleoanthropology in college and teaching genetics and evolutionary theory. Where do your ideas come from?

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My 'ideas', which if you actually look are in fact questions, come from curiosity. Every post you've made in this thread and the other has asked me to simply accept your (self-asserted) authority unquestioningly - can you please just take it as read that I don't?

So when I ask 'where are you getting this?' I am not asking for a resume, or what you do for a living. I am asking you what studies you can cite that unequivocally show (or even strongly imply) that the ideas you set forth actually exist in the real world. You have yet to do this - you have yet to even attempt this. And please accept that I'm not hostile to evidence - just lack of it. You're convinced of homosexuality's fitness and claim authority - you are in fact a teacher. Teach me!

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We don't think of the genome and how it evolves in terms of individuals, but in terms of populations. One of the most positive forces for selective fitness, is controlling the number of individuals in the population because production and reproduction are so intertwined as to be almost indistinguishable from one another.

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I'm not sure what you mean by this - are you arguing for gayness as a population-size regulator? Very difficult to accept without resorting to group-selectionism. And if you're not arguing that, what exactly do you mean?

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Ejecting gay persons from our families and communities is counter to reproductive success for the population as a whole.



Not anymore, by your own lights.


I have no idea what this means.

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Find that hard to believe. I mean that even if what you say is true of our primitive ancestors, the same does not hold true today. There is absolutely no reason to suppose that the disappearance tomorrow of all forms of homosexuality would in any way reduce our reproductive fitness, not by any model presented - even if that model is valid. And your very argument is that gayness contributed at least at one time to reproductive fitness. Pretty basic, and it was just a comment. I only felt the need to re-iterate homophobia's moral repugnance because I am very sure many people here - you included - suspect me of some unstated anti-gay agenda. The (deleted) part of your first repsonse about 'minding my own business' made that pretty clear.

Re: Random Question About Genetic Traits
 

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So when I ask 'where are you getting this?' I am not asking for a resume, or what you do for a living. I am asking you what studies you can cite that unequivocally show (or even strongly imply) that the ideas you set forth actually exist in the real world. You have yet to do this - you have yet to even attempt this. And please accept that I'm not hostile to evidence - just lack of it. You're convinced of homosexuality's fitness and claim authority - you are in fact a teacher. Teach me!

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Sure, how do you want to pay? Or, if you live near a university or really good library, hie ye forth and learn.

I wasn't arguing for anything, I was discussing a topic. I am posting on a message board - not lecturing or debating.

This ain't Oxford, it's a poker forum.

Re: Random Question About Genetic Traits
 

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Find that hard to believe. I mean that even if what you say is true of our primitive ancestors, the same does not hold true today. There is absolutely no reason to suppose that the disappearance tomorrow of all forms of homosexuality would in any way reduce our reproductive fitness, not by any model presented - even if that model is valid.

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"Absolutely no reason..?" OK, do you know the difference between "reproductive firness" and "Darwinian fitness?" In Darwinian fitness the "fittest" individual is the one who survives to have the most offspring that have the most offspring.

Studies (easy to find in that library you are going to visit) show that in rat populatiuons, same sex behaviors increase dramatically when poulation increases and space and food resources diminish.

As to modern Western culture: gay people reproduce, quite frequently. I have no studies, just have known a lot of gay folks. HOWEVER-

Neither you nor I know the imapact of 10-18% of the population suddenly becoming "straight." If even half of these people formed couples and produced 2.6 children in the next ten years, ... well, you do the math. What impact do you think there would be?

Re: Random Question About Genetic Traits
 

Do yourself a favour and never mention your profession in discussion if it's just something to lend a whiff of authority to your unsubstantiated claims. What you end up saying is that at least your armchair has a big shiny plaque on it - big deal.

Re: Random Question About Genetic Traits
 

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Now I realise that it may be true that, say, the majority of male apes do not reproduce. Do we then see that such apes as are observed to practice something like homosexuality (can't remember which specific ones, something like 'Barber apes' but I can't quite remember it)are given responsibility for the care of the group's young? And is this role assigned to gays of both genders?

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IIRC the Bonobo chimp (what you seem to be talking about) aren't known for practicing exclusively homosexual relationships. The Bonobo are know for orgy type situations where individuals will have sex pretty much indiscriminately with either sex. These orgies take place during times of stress or conflict between members and are generally viewed as ways to ease that tension and reaffirm and strengthen bonds between individuals.

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Vertebrates tend to invest far more in one batch or litter (to varying degrees) - primates more than most vetebrates, and humans more than any other primate

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Its still well under 50% of mammals that manage to reproduce.

I would also simply say that there are innumerable possibilities as the environment is constantly in flux. What might be a slight detriment under certain conditions could end up being a major benefit during a severe event (like a drought). These things aren't always obvious since they are not the normal conditions we observe the animals under.