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Research sheds light on benefits of multiple mates - Comments

nickthelight's Avatar Comment 1 by nickthelight

"At this stage the researchers do not know what implications these findings might have for understanding human reproduction. However, it is possible that some types of male fertility disorder are caused by the manipulation of selfish genes".

Begging to be misinterpreted.

Fri, 21 Nov 2008 02:08:00 UTC | #274107

beeline's Avatar Comment 2 by beeline

This article would have been made considerably clearer if the word 'selfish' had been left out entirely. Yes, this genetic trait does exemplify the process very well (and in a fascinatingly counter-intuitive manner), and you can easily see why Richard used the word 'selfish' in his title, but the way it's used here doesn't actually help explain anything.

As nickthelight says above, misinterpretation is very likely as the two different contexts of our understanding of 'selfish' are conflated: 'genetic selfishness' concerns genes whose frequency in the gene pool increases, irrespective of the benefit to their host individuals, whereas 'individual selfishness' is a psychological trait that maximises the benefit to an individual.

Still fascinating, though, and a great experiment.

Fri, 21 Nov 2008 03:33:00 UTC | #274134

ev-love's Avatar Comment 3 by ev-love

"As nickthelight says above, misinterpretation is very likely as the two different contexts of our understanding of 'selfish' are conflated: 'genetic selfishness' concerns genes whose frequency in the gene pool increases, irrespective of the benefit to their host individuals, whereas 'individual selfishness' is a psychological trait that maximises the benefit to an individual."

Thank you, beeline,

I think I’d pretty much understood that all along, but in conversation recently I could not explain the idea with anything like your clarity. Very helpful!

ev-love

Fri, 21 Nov 2008 04:20:00 UTC | #274154

beeline's Avatar Comment 4 by beeline

Heh - I'm still not sure I can do it in conversation either, without stumbling and pausing for thought a great deal, during which attention invariably wanders.

I'm constantly amazed and frustrated at how hard it is to explain things clearly 'on my feet', especially when there is a barrage of questions coming the other way at the same time. I'd make a hopeless teacher, I expect. I'm beginning to realise why, therefore, the internet is such a useful medium for debate and conversation: people have longer to articulate themselves properly, and what they do end up saying is there for everyone to see (including themselves).

All it requires is that people use it cooperatively and maturely, which is the major stumbling block, of course, when egos are at stake.

Fri, 21 Nov 2008 06:18:00 UTC | #274258

Ishruul's Avatar Comment 5 by Ishruul

I have to hide this study from my wife. It could cause her to seek out load of mate in order to preserve our specie.

I guess the religious cavemen knew this was coming.

Fri, 21 Nov 2008 06:58:00 UTC | #274285

SilentMike's Avatar Comment 6 by SilentMike

I believe the term "ultra-selfish gene" is sometimes used for genes as the one describe, that actually hurt their partners in the indivudual's body in order to further their own survival.

See here:

http://www.geodata.soton.ac.uk/biology/gene.html

Fri, 21 Nov 2008 06:59:00 UTC | #274286

BananaOfDoom's Avatar Comment 7 by BananaOfDoom

Comment #288081 by beeline:

I, too, have this problem. It's why I'm constantly in awe of Christopher Hitchens' ability to convey exactly what he wants to say without pause for suitable wording.

Fri, 21 Nov 2008 07:01:00 UTC | #274290

godskesen's Avatar Comment 8 by godskesen

Very interesting...

Of course we're pretty sure that, in the case of humans, sperm competition and cuckoldry also plays a part...

@ beeline - On the meaning of 'selfish':
There's also a different aspect. There's isn't complete agreement about what is meant by 'selfish'. Richard's (and others) sense is that all genes can be intuitively described as selfish, because evolution occurs at the level of the gene, not the organism, not the group.
The other sense, which is the one used in this article, is that genes are only selfish in they promote their own survival at the expense of other genes (or the survival machine).

Edit: 'Ultra-sefish' is way of distinguishing

Fri, 21 Nov 2008 07:06:00 UTC | #274292

Aztek's Avatar Comment 9 by Aztek

"The driving forces for this practice, known as 'polyandry', have been a mystery for evolutionary biologists for decades."

It has?

I thought they have come up with several explanations already. If women mate with several men there might always be a chance that anyone of the men is the father of the child. Therfore all men are somewhat willing to take care of the child, because it might be their's. In this way the female gets more resources for the child which of course improves its chances of survival.

Secondly, when there are little resources for a population, all men can't provide for a wife of their own. So each of the women gather a group of men around them who share the wife and provide for the child, no matter who is the father. In this way family units with one female and several males are born. In the opposite situation, when there are a lot of resources for a population, a man can afford to have one or even several wives. In a situation like this families with one man and several wifes are born.

Then of course the woman attempts to have children with the most diverse combination of genes as possible. Having many men helps.

Fri, 21 Nov 2008 07:48:00 UTC | #274306

Jeremy Nel's Avatar Comment 10 by Jeremy Nel

The 'temptation' for genes to become renegades, subverting the "good of the individual genome" for their own replication, is eternal. Should one arise, however, any genes that would suppress their effects would be favoured. As Maynard Smith once put it, since there there are many possible loci (and hence many possible suppressor mutations), the rest of the genome usually wins the contest.

In this case, the 'ultra-selfish' mutation occurs on the X chromosome and aims to increase its representation in the next generation by ensuring that any sperm carry X chromosomes. Why should the female's genes put up a fight, though? Probably because there is a selection pressure against producing offspring of the majority sex (provided the 'costs' of producing either sex are equal, as Fisher showed).

For me, the interesting point of this article is that the suppressor gene(s) fight the outlaw one even though their respective proximal phenotypic effects are in different bodies!

Have I gotten this all right?

Fri, 21 Nov 2008 07:48:00 UTC | #274307

aquilacane's Avatar Comment 11 by aquilacane

"In this study females evolved to mate with more partners when they were exposed to males carrying this selfish gene."

Is it possible that:

In this study females that naturally mate with more partners (due to a recessive trait that evolved in earlier ancestors) became dominant when they were exposed to males carrying this 'selfish' gene. This propagated a lower instance of females that mate with only one partner, thus propelling the recessive trait into a dominant position. The byproduct of this new dominant trait is an evolution in the mating habits of these isolated fruit flies.

Fri, 21 Nov 2008 09:35:00 UTC | #274354

alexhouse's Avatar Comment 12 by alexhouse

I am surprised that more of these game theory type situations haven't been explored to the limits of boredom. I guess if we were academics most of this would have been beyond note.
BTW Ishruul - I think your avatar rocks and I know there is no way I can change you but it scares the hell out of my daughter. She runs to her room when she looks over my shoulder. Any chance?

Fri, 21 Nov 2008 12:47:00 UTC | #274433

D'Arcy's Avatar Comment 13 by D'Arcy

I may be mistaken, but I seem to remember an article some years ago about the mating habits of the damsel fly. The females mate with many different males. The males' strategy is to extract the sperm already deposited before they release their own sperm.

Let me know if I got it wrong.

Fri, 21 Nov 2008 12:56:00 UTC | #274441

LeeLeeOne's Avatar Comment 14 by LeeLeeOne

"Selfish genes occur at random as a result of mutations. They spread quickly through populations because they subvert normal patterns of inheritance, increasing their presence in the next generation."

I am having difficulty understanding this particular statement. If selfish genes result as a mutation, would they no longer be considered truly "selfish" because they are subverting 'normal' patterns to conform to their 'norm', thus ultimately reproducing for the eventual resulting population that arises - the greater good versus the indivdual good?

Fri, 21 Nov 2008 15:36:00 UTC | #274520

qomak's Avatar Comment 15 by qomak

Females of most species, including many mammals, mate with multiple partners. The driving forces for this practice, known as 'polyandry', have been a mystery for evolutionary biologists for decades. This research suggests that polyandry could be the result of females adapting to avoid producing offspring carrying selfish genetic elements that reduce male fertility.


A while back I finished reading "Dr. Tatiana's sex advice to all creation" (which is a marvellous read) and in there many theories have been explained. In fact, avoiding mating a male with crippling genes is mentioned many times, for instance in the case of the bees, if I remember correctly.

The rest of the article was more interesting though.

Fri, 21 Nov 2008 16:25:00 UTC | #274533

Christopher Davis's Avatar Comment 16 by Christopher Davis

jeremynel,

You asked..."Why should the female's genes put up a fight, though'"

I suspect that females are better able to spread their genes if they bear sons. Every male offspring will possess ~1/2 a females genome so every grandchild generated by a male offspring will carry ~1/4 of her genome. Same holds true for a female offspring, but male offspring tend to be more fecund...especially if they are in an environment where females outnumber males.

The mutation described in this article would effectively limit the number of males in a population, therefore any female which had a "counter-mutation" (forgive the term, I know it is terribly inaccurate) that allowed them to produce a male offspring would wind up with a plethora of grandchildren. Grandchildren who, if female, have a better chance of also being able to resist the Y-chromosome destroying mutation.

So it is not so much the female genes "fighting" the male mutation, it's just the natural statistical results of this type of gene interaction.

Fri, 21 Nov 2008 20:06:00 UTC | #274571

Jeremy Nel's Avatar Comment 17 by Jeremy Nel

Christopher,

Thanks for the comments. If I understand you correctly, I think we basically agree. (Of course, I wasn't ever suggesting the female genes "fight" the mutation in anything like a conscious manner, it must obviously be 'statistical'.)

The only point I'd add is that under NORMAL circumstances (without this renegade gene) it isn't any more profitable, on average, to produce a male than a female, in terms of 'spreading your genes'. Although it is true that males often tend to have more partners than females, since all males MUST mate with a female, the total contribution to posterity must be equal for the two sexes. The only evolutionarily stable situation is 1:1, since any minority sex automatically becomes a more profitable way to propagate your genes. And this in turn favours a bias towards making more of the minority sex, which eventually equalises out the ratios. This is why sex ratios, in humans for instance, settle around 1:1 - despite the fact that one might think that producing males would be evolutionarily favoured. (This is a slight simplification though, as it is actually 'parental expenditure' that must be equal, which explains why the stable sex ratio can differ from 1:1 in some species.)

Of course, this equilibrium is exactly what is disrupted in the above experiment, and so 'countermeasures' are taken to restore it (unconsciously, and statistically, of course).

Fri, 21 Nov 2008 22:49:00 UTC | #274589

Christopher Davis's Avatar Comment 18 by Christopher Davis

jeremynel,

We seem to be absolutely on the same page. I hope you didn't take anything I wrote earlier to be condescending...I never for a moment thought that you were suggesting conscious action at the level of the gene.

Like you said, it's all about achieving an evolutionary stable sex ratio.

Sat, 22 Nov 2008 01:40:00 UTC | #274675

Jeremy Nel's Avatar Comment 19 by Jeremy Nel

Not at all! I just valued the input - helps me make sure I'm not going off on some tangent. Thanks again, Christopher

Sat, 22 Nov 2008 08:05:00 UTC | #274867

RSP123's Avatar Comment 20 by RSP123

Laura Betzig had a paper on paternal uncertainty in humans a few years ago. It turns out that up to 30% of us (depending on locale) don't have the biological daddy we thought we did. In some species the figure is even higher. The logic of this seems obvious - if fitness is about leaving as many descendants as possible, then it will often be a wise move to copulate with many males in case any one male has a hidden genetic defect. As this study shows, such defects not only exist but can be invisible.

Wed, 26 Nov 2008 10:21:00 UTC | #277490