Eli5 Why are women so much shorter than men?
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Most women find us repulsive. So their shorter legs mean that over time the slower women , that couldnt run as fast when we get horny, are the ones that ended up getting pregnant.
They are not – heights are pretty similar, a difference of what, 10-15%? In the animal kingdom you find plenty of examples or far bigger size differences between sexes.
So, why are men slightly bigger? Men don’t get pregnant, which is something that debilitates the individual to some extent for the duration, so they are the obvious choice for defense / protection, and so it makes evolutionary sense they are stronger and larger. A male that could better defend and provide for their offspring would pass his genes on more often.
But becoming arbitrarily large is also not ideal – there are a number of downsides, like needing more resources, having to be born from and fed by a female that is much smaller can be a problem, etc. The best ratio will depend on a ton of factors, ours must have worked pretty well, we’re a very successful species.
Of course this is all applicable to the distant past, why we evolved this way – in today’s world I don’t think it would make any big difference (in terms of species survival) if men and women were the same average height.
Polygamy. Ancient times the tallest and biggest males mated with all the women and we are their ancestors. Analyzing genes shows there’s much less variation in the Y chromosome than the X. Something like 90% of women who have ever lived had children while only around 40% of men did.
Most naturally monogamous species generally have males and females the same size, like some birds.
Monogamy in humans is relatively recent in evolutionary terms and is a cultural expectation. Humans are still naturally promiscuous with promiscuity being much higher in males.
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