Research says women are getting more beautiful | Hacker News Reader

Research says women are getting more beautiful

timesonline.co.uk

27 pointspeter12332 comments

Why are beautiful women more likely to have daughters? Women only have X chromosomes to contribute to the kid, Men have X and Y, so the gender is more or less chosen by the male. Are they suggesting that the most successful men are both more likely to get the most attractive women and more likely to have daughters?

Strikes me more as correlation rather than causation, but maybe I'm missing something.

Maybe their ovules are more receptive to heavier sperm or can detect whether a sperm is XX. Or fertilized eggs that are girls attach more easily. There are a lot of ways this can be the case.

The effect's been observed with a lot of traits that benefit one sex more than the other. For example, taller parents are disproportionately likely to have sons, because height reproductively benefits a male much more than a female.

The mechanism proposed is sex-selective abortion. Apparently, women's bodies have the ability to spontaneously abort fetuses of "the wrong" sex early in the pregnancy, either by preventing implantation or by cutting off blood supply to the placenta. Many other mammals have similar mechanisms, eg. mice will abort pregnancy if they undergo a sustained lack of food.

For that matter, human sex ratios change in a famine or ice age, with many more daughters than sons being born. Women have significantly less reproductive variability than men, since their ability to bear children is largely limited by their uterus and not their socioeconomic standing. When everybody is poor, then, it makes sense for more women to be born because daughters will not be as unfavorably impacted by poverty as sons.

Are you saying that, according to this mechanism, the womb tends to abort males that will be beautiful and females that will be tall?

More that the wombs of beautiful women tend to abort males, and the wombs of tall women tend to abort females. I'm kinda curious whether this can account for male genes at all; it seems possible but pretty unlikely.

And of course, the effect is incredibly tiny, but averaged over millions of human beings can create noticeable differences in sex ratios.

does that mean therefore that there are NOT 3 billion females and 3 billion males in the world, since, if it is not just about the sperm race and our bodies have mechanisms to determine the chances of survival of the foetus, then it is no longer 50/50?

The sperm race isn't 50/50 either. The y-sperm is slightly lighter than the x-sperm and thus slightly faster. On the other hand, women tend to live longer.

It's never exactly 50/50; generally more males are born but die sooner every step from there.

World-wide there are 107 men born for every 100 women. As women tend to get older the overall difference is 101/100. It also differs per country, and possibly other groupings.

Some numbers are in: https://www.cia.gov/library/publications/the-world-factbook/...

It's worth noting that a single beautiful mother does not birth the whole population, nor does a tall mother.

>The mechanism proposed is sex-selective abortion. Apparently, women's bodies have the ability to spontaneously abort fetuses of "the wrong" sex early in the pregnancy

Ah, thanks for clarifying. So then this doesn't account for height/beauty/etc. input from the male? I guess that still sort of makes sense.

That's interesting. Maybe King Henry VIII was on to something after all.

Plus one

For that matter, human sex ratios change in a famine or ice age, with many more daughters than sons being born.

Aha! So beautiful women who are constantly on diets trick their bodies into thinking it's a famine - thus more girls are born?

Well, if you believe some of the stuff behind the http://en.wikipedia.org/wiki/Shettles_Method for choosing the gender of your children, you could come to all kinds of theories as to the causation...

E.g., maybe men with beautiful wives don't wait for ovulation, rather they're at it all the time? I'll leave further possibilities to your imagination ;)

My guess is that this is happening because food is not a limiting factor right now, nor has it been in the last century or so. This meant that the canon of female beauty changed from plump to toned, because it was suddenly more important to reveal neoteny than to reveal resilience to famine. That's just for starters.

With cheap food for everyone, everything changes. Men become taller (Americans, arguably the group which has not suffered famines for the longest period of time, is the tallest in the world, save for small populations like Norway or the Croatians of the Dinaric Alps. IQs go up over time (Flynn effect). I can't cite a source for this, but American men are noticeably more muscular than men in other countries. America is also one of the countries with the highest rate obesity rate.

So as far as men go, you have more height, muscle mass, brain mass and fat. In fact, muscle mass, neural mass and fat are the most significant ways humans spend discretionary calories. Height is a way to accomodate greater caloric discretionary spending.

So what's happening to women is that they are spending more calories on beauty. They are becoming more attractive in all the senses that beauty can be achieved when food is not a limiting factor. Otherwise, they would already have achieved this state a long time ago.

> muscle mass, neural mass and fat are the most significant ways humans spend discretionary calories.

I can see the fat and the muscle, but neural mass ?

Do you have a citation for that ?

No, I don't. But I've asked doctors, and they say the nervous system takes up between 20 and 30% of a person's caloric intake. A third is spent on maintenance and two thirds on firing synapses. Apparently it's ridiculously energy-intensive to fire those things. I was surprised too.

It is also the case that humans have a huge amount of brain matter for their size. And keep in mind it does not take that much brain power to survive; in fact, there's a theory humans have evolved large brains as sexual ornamentation, as it apparently helps attract mates.

Hows this: (from yesterday) http://news.ycombinator.com/item?id=725333

Yes, it uses energy, because it has chemical reactions going on.

But that does not make it structurally heavier.

Nor do I expect my nervous system to gain in weight significantly when I have an excess budget of calories.

I'd expect to get fatter though.

> Americans, arguably the group which has not suffered famines for the longest period of time, is the tallest in the world,

Untrue. The Dutch seem to be taller than Americans: http://www.sfgate.com/cgi-bin/article.cgi?f=/n/a/2006/09/15/...

In fact, "[a study] conducted by the University of Munich and Princeton University, found that the United States had the shortest population in the industrialized world". [http://abcnews.go.com/GMA/story?id=3293191]

It seems Americans are even shrinking: http://www.guardian.co.uk/world/2004/apr/04/usa

Well put. Was just gonna quote some of these sources. The author of these studies was one of my professors :)

I don't know what they mean that the US has the shortest population in the industrial world. Japan is industrialized, and the average Japanese is shorter than the average American.

I'd call the Dutch a small population...but yes, you are right. They're not the tallest. But going from Chile to US, it's astounding how much taller people there are.

that's probably due to the growth hormones that are injected into the meat we eat

http://www.ehbonline.org/article/S1090-5138(09)00027-0/abstr...

Physical attractiveness and reproductive success in humans: evidence from the late 20th century United States☆

Markus Jokela

Received 9 February 2009; accepted 23 March 2009. published online 12 May 2009.

Abstract

Physical attractiveness has been associated with mating behavior, but its role in reproductive success of contemporary humans has received surprisingly little attention. In the Wisconsin Longitudinal Study (1244 women, 997 men born between 1937 and 1940), we examined whether attractiveness assessed from photographs taken at age ∼18 years predicted the number of biological children at age 53–56 years. In women, attractiveness predicted higher reproductive success in a nonlinear fashion, so that attractive (second highest quartile) women had 16% and very attractive (highest quartile) women 6% more children than their less attractive counterparts. In men, there was a threshold effect so that men in the lowest attractiveness quartile had 13% fewer children than others who did not differ from each other in the average number of children. These associations were partly but not completely accounted for by attractive participants' increased marriage probability. A linear regression analysis indicated relatively weak directional selection gradient for attractiveness (β=0.06 in women, β=0.07 in men). These findings indicate that physical attractiveness may be associated with reproductive success in humans living in industrialized settings.