Sexual SelectionSexual Selection

Psychology 3107Psychology 3107

IntroductionIntroduction

A species’ ecology A species’ ecology should dictate what should dictate what traits are optimal traits are optimal

Natural selectionNatural selection

Explain this thenExplain this then

What is Sexual Selection?What is Sexual Selection?

Sexual selection is ‘the advantage which Sexual selection is ‘the advantage which certain individuals have over others of the certain individuals have over others of the same sex… in exlcusive relation to same sex… in exlcusive relation to reproduction’ Charles Darwinreproduction’ Charles Darwin

So, it is NOT about the environment, but So, it is NOT about the environment, but about mate choice really about mate choice really

Intra Sexual SelectionIntra Sexual Selection

Usually Male – MaleUsually Male – Male

LeksLeks

Body SizeBody Size

WeaponsWeapons

Could be all of the above, some of the Could be all of the above, some of the above, or, of course, othersabove, or, of course, others OrnamentationalOrnamentational

Inter Sexual SelectionInter Sexual Selection

Once you ‘win’ (you Once you ‘win’ (you being a male) then being a male) then inter sexual selection inter sexual selection startsstartsFemales choosing Females choosing males (usually)males (usually)This can lead to This can lead to strange things like strange things like peacock feathers, peacock feathers, combs, antlers or combs, antlers or stupidly long tails!stupidly long tails!

Inter sexual selectionInter sexual selection

Why would a female choose something so Why would a female choose something so ridiculous?ridiculous?

Could indicate good genesCould indicate good genes

Could indicate strengthCould indicate strength

Could indicate parasite resistanceCould indicate parasite resistance

Could just be nutsCould just be nuts Runaway selectionRunaway selection

QuestionsQuestions

Can I buy you a drink?Can I buy you a drink?

Would you like to go out with me?Would you like to go out with me?

Wanna have sex?Wanna have sex?

(Clark and Hatfield, 1989)(Clark and Hatfield, 1989)

73 percent of men73 percent of men

NO womenNO women

There is a difference here, why deny it?There is a difference here, why deny it?

Sexual selection in humansSexual selection in humans

Intra sexual and intersexual selectionIntra sexual and intersexual selection

A woman can produce one child a yearA woman can produce one child a year

A guy can produce as many as he can…A guy can produce as many as he can…

Paternal investment slows reproductive Paternal investment slows reproductive rates of menrates of men

So what are the humans like, are we like So what are the humans like, are we like deer or like well the Vulcans…deer or like well the Vulcans…

Then againThen again

We are both, men and women, still choosyWe are both, men and women, still choosy

27 percent of men did say no to the offer 27 percent of men did say no to the offer of sexof sex

This would not happen in other mammals This would not happen in other mammals usuallyusually

So both sexes are choosy, it just depends So both sexes are choosy, it just depends on what foron what for

Beauty is in the adaptations of the Beauty is in the adaptations of the beholder…beholder…

Well maybe we are after good genes Well maybe we are after good genes (seems reasonable…)(seems reasonable…)

Maybe attractiveness is related to parasite Maybe attractiveness is related to parasite loadload

We have to choose a mate that is most We have to choose a mate that is most likely to produce pathogen resistant likely to produce pathogen resistant offspringoffspring

MHCMHC

MHC genes build our immune systemMHC genes build our immune system

We should prefer mates that are similar in We should prefer mates that are similar in most characteristics but different in MHC most characteristics but different in MHC genesgenes

Boy how could we test that?Boy how could we test that?

Umm, well go for a run and let me sniff Umm, well go for a run and let me sniff your armpits…your armpits…

Parental investmentParental investment

Men’s is economic Men’s is economic

Women’s is physiologicalWomen’s is physiological

So what should we prefer then?So what should we prefer then?

Women should rate economic stuff (oh say Women should rate economic stuff (oh say salary) as more important than men dosalary) as more important than men do

But I thought women were in the work But I thought women were in the work force and all that, and all the socializationforce and all that, and all the socialization

Yes of courseYes of course

Is that your wallet in your pocket or Is that your wallet in your pocket or are you just glad to see me?are you just glad to see me?

Personal adsPersonal ads

11 to 1 ratio!11 to 1 ratio!

Ask single women, they rate it more Ask single women, they rate it more important, much more important, than men important, much more important, than men dodo

Put downs of others’ resource acquiring Put downs of others’ resource acquiring abilityability

THIS IS CROSS CULTURALTHIS IS CROSS CULTURAL

Structured powerlessnessStructured powerlessness

So, maybe women prefer this because, So, maybe women prefer this because, well that is how stuff works, I mean guys well that is how stuff works, I mean guys just have more access, so it makes sense just have more access, so it makes sense to prefer guys with bigger walletsto prefer guys with bigger wallets

So then it would follow that women with So then it would follow that women with much access to power would not care much access to power would not care about a man’s earning powerabout a man’s earning power

Ummm no…Ummm no…

Newlyweds studied by David BussNewlyweds studied by David Buss

No relationship between income and No relationship between income and importance in men, a nice positive one in importance in men, a nice positive one in womenwomen

It turns out, in fact, that women that will It turns out, in fact, that women that will probably make more, or do make more probably make more, or do make more actually care MORE about the earning actually care MORE about the earning power of their potential mate!power of their potential mate!

Ok, what do men want?Ok, what do men want?

Women, lots and lots of fertile women….Women, lots and lots of fertile women….

Men like youthMen like youth

Men like clear skinMen like clear skin

Men like symmetryMen like symmetry

The waist to hip ratio is a good indicator of The waist to hip ratio is a good indicator of fertilityfertility

.7 or so.7 or so

Strategies mixed and pureStrategies mixed and pure

People are unfaithfulPeople are unfaithful

Hard to get rates, though the study at the Hard to get rates, though the study at the beginning gives us an ideabeginning gives us an idea

When messing around, what do we When messing around, what do we prefer?prefer?

Men’s standards are lower….Men’s standards are lower….

jealousyjealousy

RememberRemember

Do NOT fall for the naturalistic fallacyDo NOT fall for the naturalistic fallacy

Nobody is saying we do this consciously Nobody is saying we do this consciously

Interesting though that now with women Interesting though that now with women increasingly in the workforce and with men increasingly in the workforce and with men doing more childcare these differences doing more childcare these differences seem to be steadyseem to be steady

ConclusionsConclusions

Traits may co evolve with preferencesTraits may co evolve with preferences

The hypotheses ARE NOT mutually The hypotheses ARE NOT mutually exclusiveexclusive

Perceptual mechanisms and their Perceptual mechanisms and their constraints play a big role (Shettleworth, constraints play a big role (Shettleworth, 1998)1998)