Saturday, February 16, 2019

Data: Are athletes smarter or dumber than others?

There are positive correlations between IQ and both longevity and height.  Many genes underlie these traits -- it looks like there are health-promoting genes that manifest themselves not only through a long life but perhaps a better functioning brain and ending up taller. And a smart/tall/long-lived person might also have a comparatively small number of mutations that work against health.

Does being an athlete fit in with the rest of these traits?  One might expect height and athleticism to be correlated simply because popular sports like basketball and football favor bigger people.  How about IQ and being a good athlete?  Here are the correlations for IQ and self-rated athletic ability (GSS):

White males (n = 440)   -.05
White females (n = 553)  .01
Black males (n = 74)  -.09
Black females (n = 103)  -.14

For all demographic groups, IQ and athletic ability are either not correlated or a negatively correlated. It does not appear to be the case that there are genes that promote both at the same time (or that subtract from both simultaneously).

Thursday, February 14, 2019

Data: Do brains get you more sex?

Evolutionary psychologist Geoffrey posted the claim on Twitter recently that human cognitive abilities evolved to attract sexual partners.  Greg Cochran responded that there is no evidence that sexual selection has been a significant driver of mental abilities.

Do intelligent people get more sex?  And bottom line: do they end up with more children?  The General Social Survey measures IQ with a vocabulary quiz, so we're measuring verbal ability, a form of intelligence Miller would think is more important for courting than, say, math ability.  I'll focus on ages 18-35 since this is a critical time for sexual competition, and frequency varies with age. Here's a graph of the frequency of sex over the past year (GSS, whites, N = 12,757):

Sexual frequency peaks for men at a mean IQ of 98.  The mean is 3.8 -- 3 means two or three times per month, and 4 means weekly.

Sexual frequency drops off for higher IQ mean, but then it reverses for men in the highest IQ category.  Their average is 3.7.

(Notice how the lowest IQ women have the most sex by far.)

What about kids?  We've already documented that high IQ women have fewer kids, but let's focus on men. This graph is for whites ages 45-60:

For men, peak family size is for those with IQs of 77.  Men at the highest IQ level average fewer children than almost any other group.

There's little evidence here for a verbal IQ payoff.

Tuesday, February 12, 2019

Data: Do religious men have larger families? Do religious people idealize larger families?

We saw in the last post that religious women are having more babies than women who never go to church. What about men?  Here a graph for number of children for men ages 45-60 (GSS, N = 1,251):

The pattern for men is even clearer than for women: guys who attend more than once a week have a much higher mean (2.38) than those who never go (1.61). That's roughly half of a standard deviation difference.

Is this religiosity-fertility link explained at all by differences in attitudes?  Do religious people want more kids?  Look at the graph for the same age ranges (GSS, N = 2,173):

Males are green, and females are purple (I'm a dude, so I won't try to give more precise colors).

There is a small tendency for more religious people to idealize larger families. It seems too small to explain much of the reason why the religious have bigger families. It's probably due to getting married earlier and less willingness to get an abortion if you get a surprise.

NOTE: You have read an updated version.  The earlier version had the error of leaving in cases of those who answered "whatever number people want," cases that were scored an 8.  The results you see above omit these cases (about 6% of the sample). 

Monday, February 11, 2019

Data: The end of religion? Maybe not.

Social thinkers have been predicting the end of religion for many decades.  For example, Auguste Comte (1798-1857) predicted that religious faith would decline as scientific knowledge spread.

Over the past two centuries, religion has proven to be more resilient than thought, but there has been a serious decline in regular church attendance in the US in recent decades, and confidence in the existence of God has slipped some, too.

Modernists like Comte were not aware that at least one powerful factor might work against their hopes of a secular world: genes.  Studies have found that religiosity is influenced significantly by genetic differences. 

And there's a related factor: the correlation between religious involvement and family size.  Look at current data for American women (General Social Survey, women ages 40-55, N= 1,441):

Women who never go to church average 1.92 children, while those who go more than once a week have a mean of 2.48 offspring.  The gap between the two groups is about four-tenths of a standard deviation, a medium-size difference.

Notice how the least fertile women (1.66 kids) attend once per year.  (I'll document in a future post that atheist women have more kids than agnostics.)

Religious people tend to be more conscientious and agreeable than the irreligious, and fertility differences are favoring these genetically-influenced traits.

If the greater fertility of religious women turns out to be a long-term trend, evolution might work against secularization.  Combine this with the mass movement of religious Muslims, sub-Saharan Africans, and Hispanics to the developed world, and Comte's vision might be undermined. 

Wednesday, February 06, 2019

Data: The most athletic women have the fewest kids

Now that I've got a little more confidence that self-rated athletic ability has some validity to it (I also observed that it drops markedly with age), I looked to see if athletic people have fewer children. Here's the graph for women ages 40-55 (General Social Survey, N = 401):

American women who say that "athletic" describes them very well average only 1.58 children, while all the less athletic groups have roughly 2.1 kids.

What about men?  Here's a graph for them (N = 317):

With men, we see a U-shaped relationship: the very athletic group has a mean of 2.39 offspring, and the least athletic men average 2.31 kids.  The average athletic group has the smallest families: a mean of only 1.66 kids.

We could interpret this pattern to mean that highly athletic men are more attractive to women and consequently have more mating opportunities, while the least athletic tend to be low testosterone men who are highly committed to family, which is an alternative path to a large family.

The overall results suggest a mixed trend.  What sticks out to me is that athleticism among women shows that same dysgenic trend with see with traits like IQ, education, and health: the top scoring females consistently have the fewest kids.

And let's not forget the study I linked to that found that athletic performance is highly influenced by genes (heritability = .66).

Tuesday, February 05, 2019

Data: Sex and race differences in self-rated athletic ability

One study of athletic performance put heritability at .66.  In plain English, two-thirds of the differences in athletic ability are explained by genetic differences.

General Social Survey participants were asked to rate how athletic they are on a scale from 1 to 5.  I calculated the means for sex and race combinations (N = 2,373):

Black men rate themselves as most athletic with a mean of 3.57.  White women (2.58) and women of some other race (2.56) come in at the bottom.  The gap between black men and other-race women is nine-tenths of a standard deviation (SD) -- a big difference.

If we focus on just men, the black-white difference is one-third of an SD -- a small advantage for black men.

The biggest within-race gap is among blacks: the male advantage over females is three-quarters of an SD.  The graph doesn't show the overall sex difference: it's over half of an SD.

While it's difficult to rate oneself objectively, these self-ratings seem to have some validity.

Sunday, February 03, 2019

Data: Survival of the fattest?

We saw in a recent post that the women with poor health have the most kids.  Is this true for heavy women, too?  Yes, it is: look at this graph (General Social Survey, self-reported weight, N = 200):

Women with one child are the lightest group with a mean of 165.6 pounds.  Compare this to the heaviest group: Women with seven children weigh an average of 208.5 pounds. The difference is roughly one standard deviation -- huge, no pun intended.

Of course, it's hard for a woman to lose the weight she gains from being pregnant, but it is also possible that genes underlie both weight and fertility.

For example, perhaps women who score low on conscientiousness (self-discipline, long-term planning) lack control over both eating and fertility.

Americans are likely to get fatter and fatter as the generations go by.  If civilization eventually collapses under all the dysgenic trends I have been documenting lately, these fat Americans might finally lose weight due to food shortages.

UPDATE: Readers might suspect that a respondent's weight is due to her height, and perhaps tall women are having more babies.  I checked: fertility does not vary by height. 

Data: Are athletes smarter or dumber than others?

There are positive correlations between IQ and both longevity and height.  Many genes underlie these traits -- it looks like there are healt...