Why humans and elephants are furless?
I was looking in the mirror and thinking about wrinkles, and it occurred to
me that if only we had fur, no one could tell a 35-year old from a 20-year
old by looking. And then it occurred to me that humans are almost the only
mammal with no fur, excepting elephants, rhinos, hippos, and naked mole rates;
and humans are also almost the only mammal that lives long enough for age to
be a negative rather than a positive factor in mate selection, excepting
elephants, rhinos, and hippos.
So what's up with the naked mole rats?
No, actually the point is that perhaps facial hairlessness is a result
of group selection to enable people to pick out younger mates. It
is a difficult case for group selection, though, because providing
evidence of aging on your face seems like a maladaptive trait for any
individual who has it.