Sexual selection in humansWHY are men’s muscles so much bigger than women’s? Partly, of course,
because men do the fighting and hunting. But also, perhaps, because
women like men who can do these things well, and are thus attracted to
muscular men. Both phenomena—competing with members of the same
sex and showing off to members of the opposite—are subject to a form of
evolution known as sexual selection. It is sexual selection that created the
deer’s antlers and the peacock’s tail, and William Lassek of the University
of Pittsburgh and Steven Gaulin of the University of California, Santa
Barbara, think it explains men’s muscles as well.
... the National Health and Nutrition Examination Survey, which followed 12,000
American men and women over the course of six years...there is a cost to being muscly:
men’s immune systems are less effective than those of women (which was known before), and become worse the more muscular
the men are (which was not).
The benefits, however, were there, as well. The more muscular a man, the more sexual partners he
reported, both in the past year and over his lifetime, and the earlier his first sexual experience was likely
to have been...In the past, the strong man would have had better mating opportunities in the short term,
but the skinny guy who outlived him could have had just as much reproductive success over the course of
his longer life.
The irony for the skinny guy is that the laws which protect him from aggression also make it less likely
that the hulk will fight himself into an early grave. Modern medicine, meanwhile, means the hulk’s
weakened immune system is less likely to expose him to lethal infection. Time, then, to get the weights
out, and start pumping iron.
Mr Muscle
Economist Aug 29th 2009