Showing posts with label sexual dimorphism. Show all posts
Showing posts with label sexual dimorphism. Show all posts

Sunday, October 31, 2010

Why Are Women Pretty? Or, Why Do Men Like Porn?

Why isn't it men that wear makeup?
Why is that when you walk down the makeup aisle, the hair aisle they aren't monopolized  by products for males?
Why do department stores have a vastly disproportionate amount of female apparel and clothing?
Why is it that 87% of all plastic surgery is performed on women?
Why don't men go and get their nails done?
Why aren't men the ones that are most likely to have long, expensive, complicated, time consuming hair dos?  Why isn't it that men are the ones that take FOREVER to get ready to go somewhere?
Why isn't a diamond a guy's best friend?

Or, why is the human mating system so different from the vast majority of other animals?

Nearly across the board it's the males of a species that display.  They come in every shade and hue conceivable.  They hum, honk, buzz, vibrate, dance, sing, knock antlers, bash horns, strut, display...Their males are, simply put, pretty.

It isn't that human males don't have their own system of showing off--muscles, sports, status displays, material wealth, etc.  It's just that you'd kinda expect men to be prettier if they were like seemingly all other animals, but it's the females of our species that are beautiful, that preen, that strut and that display and not the males.

We seem to have everything backwards.

Why?

1)  Males that were picky had offspring that were more likely to survive and reproduce.

2)  Females that had certain attributes could communicate some perceived advantage and make them more likely to mate.

3)  There were enough females that males could be choosy.

4)  Being able to care for a child is much more critical to humans than it is to other animals.

Let's look at some of the human female attributes that men find appealing and parse them a smidge.  Hopefully, what we can learn is how that we're distinct from other animals.

Breasts - Why not start with the obvious?  We're the only ape, let alone mammal that make a display out of their mammary glands when they aren't lactating.  This, like several others to follow highlights a theme that child rearing is unusually difficult, costly, involved, prolonged in humans.  Our children are ridiculously vulnerable when they're born.  Wildebeest newborns need to be able to stand within a few minutes or they're abandoned.  Human newborns can't even lift their head or roll over and won't be able to walk for an entire year!!!  Animal Kingdom wide, that's shocking!

Nearly a third of a mother's resting metabolism goes into breast feeding.  So, men want women that can hack that Herculean task.

Hips - "I will greatly increase your pains in childbearing; with pain you will give birth to children." --Yahweh

Humans run a fine line between wanting speed and ease of locomotion, which has been linked to narrow hips and wanting wider hips for bigger brained babies.  Wide hips might be a more recent desired trait that shows a shifting emphasis on braininess.





Buttocks - Fat.  Glorious fat.  Energy reserves = successful pregnancies and ability to provide enough milk.

Taken to the extreme this produces a condition that's known as steatopygia.  




Eyelashes - why is having long eyelashes considered feminine?  That's an interesting question.  It might have something to do with youthfulness, which we'll talk more about below.  Or, maybe something to do not with eyelash length, but in eyelash prominence.  Maybe masculine foreheads that have pronounced brows might conceal eyelashes, so obvious eyelashes indicate feminine skull structures.  I have no clue, though...


Eyebrows - Why do women pluck their eyebrows to make them thinner?  Well, because big bushy eyebrows are masculine.  Why?  Because it externally communicates something about the internal hormonal balance.



Lips - We're the only ape to really have lips - red, puffy, voluptuous lips.  I've read some anthropologists speculate that this is some kind of throw back to the red, puffy, engorged vulvas that our ancestors were wild about (like a whole host of other simians have today).  That may or may not be, but it is possible to see this body part, like many, as a dip stick - it lets you know the health of the organism.  Moist (think lip gloss), red (rouge) lips contrast dry, pale or blue lips.  Doubtless, there is also a hormonal connection - it's known that higher estrogen levels = fuller lips.  Maybe it's yet another communication adaptation - red lips make for more obvious lip expressions.

Or, what if lips evolved simply for kissing?

To kiss.
To be kissable.




Sclera - This isn't specific to women, but it is interesting.  We're the only ape that has white scleras (the whites of the eyes).  Other apes have brown or dark sclera so as to camouflage their eyes.  The whitening of our sclera could have happened as another dip stick adaptation (white shows you don't have jaundice, bloodshot eyes or malnutrition of some kind) or as yet another adaptation to increase our expressive abilities.  One study showed that human babies look where the tester looks, as opposed to how tested apes look where a face is pointing.


Eyecolor - based on the mutation rate of certain markers it's estimated that the existence of blue eyes in humans is somewhere less than 10k years.  That fact alone combined with the knowledge that it's recessive should make it shocking to think that there are areas in Europe where the prevalence exceeds 80%.  So why the proliferation?  It's sexy.  Why is it sexy?  I'm not sure there's a simple answer, but possibly because it was an indicator of desirable genetic diversity (at least initially).  There are some psychological reasons I can't quite put my finger on yet.  Please look at this picture and comment your thoughts.  Blue does seem to accentuate where the eyes are looking (like at your eyes) by giving greater contrast to the eye's aperture.  That might be why they seem so piercing.  Brown, on the other hand seems more doe-eyed and innocent.




Hips to waist ratio - Hormones.  Men prefer women  with a waist to hip ratio of 0.7.  It indicates a desirable hormonal balance.  The difference between men and women's hips/waists can be a dead give away for drag queens.  Notice the below picture.  It's instantly obvious that's a male.  Why?   Because women's hour glass figure is important to communicate internal hormonal states.

You don't have to think twice about it.  This is a male's hips and waist.  Much about hormones is communicated through the shape of our anatomy.


Youthfulness - Young women can produce more children, better nourish them and have less chromosomal abnormalities.  This is not true for men who can actually become more appealing with age (think Harrison Ford and George Clooney).  Old men that are healthy and attractive often have high status (which takes time) and therefore resources and have proven that their genes came make it through the long run.  The emphasis for women is ability to care for healthy children.  The emphasis for men is ability to provide for a child and lack of mutations.

Hair (scalp) - More recently I think hair has communicated less about being healthy and disease free, which it does quite well, but more about personality.  This is a little bit of a pet theory, but I think our head fur (follicles only grow to a certain length and then die) turned into hair (doesn't stop growing) because of what it communicated about the person that could up keep it.  Think about it.  Hair can take an enormous amount of work. Especially long hair.  One of the easiest and clearest indicators of insanity is unkempt, wild, crazy, matted hair.  Maybe, just maybe, human scalp hair developed to show that a person wasn't crazy and could wash, comb, detangle, and fix up their hair.  Something like, if a women could care for her hair, which is time consuming and difficult, she could care for a child.  It's a thought.

I've included a clip of a women crying after getting a nastey hair cut.  I watched the rest of the show and to my recollection there were several women that refused to get their hair cut.



Women communicate with hair.


Works Sighted [sic] :





Sunday, May 16, 2010

Are Humans Evolved for Polygamy or Monogamy?

Are humans naturally monogamous or polygamous?Well, what's science have to say about it?

Since there's more than one kind of polygamy, I'll split it up into multiple male partners per female (polyandry) and multiple female partners per male (polygyny).

First, a little background:  Gorillas mate in harems.  One male per 3-6 females.  Chimps on the other hand have more of a free love mating scheme.




Polyandrous Scale


Are there signs that our ancestors had many male partners?  Yes, but not we're paltry compared to some.  Here's how we can tell: let's say you're a female that has many men to choose from but you only sleep with a few.  In that case male displays become quite pronounced (think peacock tail).  On the other hand, what if a species not only has many males for the female to choose from, but she ends up sleep with many of them.  The competition between males is no longer how can I impress the girl, but how can I get my sperm to the egg more effectively or faster than the other males.

I've heard some discussion that the shape of the male glans is actually a scoop to remove other male's semen while thrusting.  So, that's one way, but a more common one among many species is a simple numbers game--overwhelm the competition with an army of sperm.  How would that change the morphology of an organism?

It would give it huge testicles.

In short, if there are many males sleeping with one female the one with the largest testicles has the best chance of winning.

So, how do human testicles compare to other species?

Gorilla: 1 ounce testicles at .02% of body weight with 50 million sperm per ejaculate.
Chimpanzee: 4 ounces testicles at .3% of body weight at 600 million sperm per ejaculate.

Human: 1.5 ounces testicles at .04-.08% body weight with 250 million sperm per ejaculate.



Summary: we're semi-promiscuous.  Our females fidelity is some where in between gorillas and chimps (but more toward the gorillas side).

There's more to the equation, though!


(Another interesting solution to this problem is to made a vaginal plug out of your semen: http://en.wikipedia.org/wiki/Mating_plug)


Polygynous Scale


Ever wonder why men are taller than women?  Why men can bench more than women?  Why they compete separately during the Olympics?

There's an evolutionary reason for that!

Here's the idea:  when there's a group of males competing for a limited number of females the strongest will have an edge.  The bigger you are, the more intimidating you are, the stronger you are, the better you can fight the more females you can win.

This is exemplified by the gorilla.  We've already said they have small testicles, so that isn't how the males have reproductive success.  What is it?  They get so big and muscular that they can kick all the other male's asses.  Gorilla males have a very, very, very well guarded harem of females.

They don't need big nuts when they've got big guns.

So, the more sexually dimorphic (skewed male/female size ratio) the more polygynous the species.  How do humans stack up?

Gorillas: males are up to 400lbs. Females are around 200 lbs. Males are 100% heavier.
Chimpanzees: males are 170-185. Females are 135-145 lbs.
Humans: males are 190.  Females, 160.  Males are 26% heavier.


Summary: we're more polygynous than chimps, but less than gorillas.

Much more could be said here, but that's something to chew on.  (Aside--high IQ has been correlated with increase monogamy in humans)



It seems conceivable that since human females put so much effort into displaying to males (makeup, cosmetic surgery, clothing, etc.) that males are often the choosers in our species.  Why be choosy? Only because you have something to lose from picking a genetically inferior female - time, effort, resources.  If there was nothing to lose then you'd have no standards.  Being choosy just may indicate that we are a particularly monogamous and caring kind of male species...On the other hand, maybe human females aren't trying to win a male so much as they are trying to keep one.

(Later addition below)
If it's such a "man's world", as some say it is, then why is polygamy out lawed in most countries?  At first blush that doesn't make any sense!  If men rule the world then you'd totally expect polygamy to be in vogue!   Is it that women prevent it to avoid exploitation?   Well, unlikely.  Think about it.  Polygamy is in the best interest of women evolutionarily.  From an evolutionary perspective what do when want out of a man?  Resources to care for a child and superior genes.  In a stratified society (which can lead into polygamy) woman can get both more resources and better genes from being with a highly successful money-bags.  Also, in a polygynous society all the women get a mate (in theory) since even the lower quality ones will be taken since a low quality woman is better than no woman.  Men on the other hand (on average) end up worse off.  One reason being what I just mentioned--in a polygynous society not all of the men get a woman.  In fact, it's interesting to note that monogamy may very well be one of the first steps towards democracy.  The average man started to collectively say that they were no longer going to let a few successful men take all the women from them.  So, contrary to some popular opinions monogamy wasn't a defense of women's rights, but of instead of men's.  I find that fascinating.