A good mate doesn't always get you good genes

[Naraoia]

This paper is a few years old, but I only heard about it in this morning's class on sexual conflict. It kinda turned my worldview upside down. Allow me to geek out about it a bit

Pischedda A, Chippindale AK (2006) Intralocus Sexual Conflict Diminishes the Benefits of Sexual Selection. PLoS Biol 4(11):e356

Basically, although one would expect that there is a point to sexual selection by mate choice, that may not always be true. Many theories of sexual selection focus on "good genes" in some way. However, in the fruit flies used in this experiment, a match between a very fit male and a very fit female produced the least fit offspring. The best males had the crappiest daughters and the best females had the crappiest sons. Moreover, a father's fitness had no effect whatsoever on the quality of his sons, although a mother's fitness correlated positively with that of her daughters.

This is because of genes that have opposite fitness effects on males and females. That's why mating with a good male guarantees you poor quality daughters: what made their father successful is likely to have the opposite effect on them. Such genes (at least in fruit flies) are concentrated quite heavily on the X chromosome (fruit flies have a similar XY sex determination system to ours, and their X chromosome is quite large), which explains why sons don't inherit their father's fitness (they don't inherit his X chromosome).

The really puzzling thing about this is that female fruit flies are choosy, and males court them quite passionately to get them to mate. Yet choosing the best males is actually counterproductive from females' point of view. Why on earth do they still do it? Do males just manipulate them so cleverly that they don't know what's good for them? Or is it a particularly pointless example of Fisher's runaway process?

There is a hypothesis that females prefer attractive males because they will father attractive sons (who will then give them lots of grandchildren), but that doesn't appear to be the case here.

Another point I found quite interesting is that similar considerations might explain why pronounced sexual dimorphism, with gaudy and extravagant males, is so common in birds and butterflies: in these groups, it's the males who have two X (or, technically, Z) chromosomes, so their sons DO inherit all that fancy stuff.

Anyway, I thought this study was quite cool. It definitely challenged my long-held ideas about sexual selection.

</evolutionary biologist geeking out>

 

[Agonaces of Susa]

So much for the debunked, refuted, and falsified Victorian Age evolutionist hypothesis that sex is all about selfish-genes.

 

[SithDoughnut]

So much for the debunked, refuted, and falsified Victorian Age evolutionist hypothesis that sex is all about selfish-genes.

I've yet to see you come up with something better that doesn't rely on debunked, refuted, falsified, quote-mined and irrelevent Victorian Age or older quotes. If this paper is the case overall, then we adjust the theory or make a new one.

Welcome to science, where theories are adjusted to fit our ever changing picture of the universe. Please leave all pre-concieved notions in the tray as you walk in.

 

[Chesterton]

Yet choosing the best males is actually counterproductive from females' point of view.

I know, right? I've been trying to tell females in bars that FOR YEARS! I oughta print that paper and carry it around with me.

 

[Naraoia]

So much for the debunked, refuted, and falsified Victorian Age evolutionist hypothesis that sex is all about selfish-genes.

Selfish genes are a Victorian Age hypothesis now?

I know, right? I've been trying to tell females in bars that FOR YEARS! I oughta print that paper and carry it around with me.

Buying them more drinks might work better

 

[BranwenUerchLlyr]

So much for the debunked, refuted, and falsified Victorian Age evolutionist hypothesis that sex is all about selfish-genes.

The "sexy sons" hypothesis is not in conflict with the concept of the "selfish" gene.

 

[Philothei]

Buying them more drinks might work better [/quote]

Yep. too dark to read the paper anyways
Thanks for the interesting paper though...

Maybe finding a "smart" mate you just chose to live with someone more interesting than the average mate? Why do fruit flies be programed to "chose the best" if it does no matter??

ah...maybe they want to impress their friends

 

[Montalban]

How do women decide which potential mate has the best genes? What method do you use?

What method do fruit flies use?

 

[BranwenUerchLlyr]

How do women decide which potential mate has the best genes? What method do you use?

What method do fruit flies use?

For human mating, see works by David Buss on evolutionary psychology.

 

[Montalban]

For human mating, see works by David Buss on evolutionary psychology.

Really, so a woman in order to choose a mate consults some evolutionary psychologist called David Buss? He must be very busy

 

[Naraoia]

How do women decide which potential mate has the best genes? What method do you use?

Ask them for a tissue sample

Jokes aside, I'm really not familiar with human mate choice literature. There seems to be some very interesting stuff out there, though. For example, that women's taste in men changes with the menstrual cycle. When we are most fertile - ovulation time - we like the more masculine, hot guys better. A macho who spreads his seed left and right is probably a good genetic father for your (sexy) sons, but less likely to help you raise them (and raising a human child, as you probably know, is no easy thing)

I think human mate choice is heavily complicated by things like cultural norms, so it may be difficult to pick out real patterns. Then again, are the cultural norms adaptive, or were they when they originated?

What method do fruit flies use?

Fruit flies let the guy sing to them and chase them around for a while before they decide if they like him [description of courtship]. I know the song is species-specific, and females are more likely to accept their own kind (though if given no choice, they'll sometimes mate with a male of another species), but I'm not sure precisely what parameters they look for among conspecific males. IIRC, various pheromones (including cuticular hydrocarbons) are also involved.

Annotated video of courtship in Drosophila melanogaster

YouTube - Fruit fly (drosophila melanogaster) courtship

For human mating, see works by David Buss on evolutionary psychology.

One of those came up in one of my classes. It was the one where males and females had to rank traits according to how important they are in a potential partner. Apparently, the first few items on the list for both sexes were identical, and the differences he was expecting and did turn up were (1) small (2) way down on the importance scale. Dunno what that means, if it means anything at all. Human behaviour is not my area, and I never followed up on this in any depth.

(IMO, questionnaires are not necessarily the best way of learning what people want in a partner anyway)

In the same module, we also heard about studies on things like how much richer does an already married man have to be than an unmarried man for women (or their families) in polygynous societies to choose him. (Although the hypothesis behind such studies concerns resources, not necessarily genes). There seems to be a lot of very interesting stuff in the human mate choice literature.

 

[BranwenUerchLlyr]

Really, so a woman in order to choose a mate consults some evolutionary psychologist called David Buss? He must be very busy

Your point is lost on me.

There are cross-cultural trends to the game of human mating as it relates to the evolution of our species--namely, behavioral vestiges of our ancestral past. David Buss has personally researched aspects of it but I find his reviews of the literature to be of greater interest to understanding human mating strategies. He has written some introductory/student reviews, so his work is a good resource to start with.

 

[BranwenUerchLlyr]

Ask them for a tissue sample

Jokes aside, I'm really not familiar with human mate choice literature. There seems to be some very interesting stuff out there, though. For example, that women's taste in men changes with the menstrual cycle. When we are most fertile - ovulation time - we like the more masculine, hot guys better. A macho who spreads his seed left and right is probably a good genetic father for your (sexy) sons, but less likely to help you raise them (and raising a human child, as you probably know, is no easy thing)

I think human mate choice is heavily complicated by things like cultural norms, so it may be difficult to pick out real patterns. Then again, are the cultural norms adaptive, or were they when they originated?

Fruit flies let the guy sing to them and chase them around for a while before they decide if they like him [description of courtship]. I know the song is species-specific, and females are more likely to accept their own kind (though if given no choice, they'll sometimes mate with a male of another species), but I'm not sure precisely what parameters they look for among conspecific males. IIRC, various pheromones (including cuticular hydrocarbons) are also involved.

Annotated video of courtship in Drosophila melanogaster

YouTube - Fruit fly (drosophila melanogaster) courtship


One of those came up in one of my classes. It was the one where males and females had to rank traits according to how important they are in a potential partner. Apparently, the first few items on the list for both sexes were identical, and the differences he was expecting and did turn up were (1) small (2) way down on the importance scale. Dunno what that means, if it means anything at all. Human behaviour is not my area, and I never followed up on this in any depth.

(IMO, questionnaires are not necessarily the best way of learning what people want in a partner anyway)

In the same module, we also heard about studies on things like how much richer does an already married man have to be than an unmarried man for women (or their families) in polygynous societies to choose him. (Although the hypothesis behind such studies concerns resources, not necessarily genes). There seems to be a lot of very interesting stuff in the human mate choice literature.

I definitely agree on the questionnaire point--what people say they look for and what they actually respond to are often quite different.

I like David Buss because his reviews are often focused on points of convergence between behavioral and biological lines of research, for instance--access to resources being a predictor of genetic fitness, or how altruism that is potentially detrimental to the individual's reproductive success can be beneficial to the proliferation of genes via kin.