What good is it to go bald?
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Of what benefit is it to human males to lose hair from the top of their head? Isn’t the purpose of hair to shade the skull so the brain is kept cool?
A distinguishing characteristic of mammals is our hair – although how much hair and where it grows varies among mammal species. A dog is generally entirely covered with hair, while a whale and a hippopotamus each has just a few hairs. Humans have hair just about everywhere except on our palms and the soles of the feet. Our thickest hair is usually on the top of the head – that hair would indeed help keep the scalp cool in the tropics – and warm in colder climates. Then why do many men – and some women – go bald? Evolutionary theory says a trait will persist if it’s advantageous – or if it’s neutral – that is, not harmful to the species. Baldness may be a neutral trait.
Some hair thinning happens commonly as we age. But pattern baldness, or alopecia, is hereditary – and may be associated with high levels of male hormones. We’re not the only primates who exhibit alopecia. A species of monkey – the stump tailed macaque – displays hereditary baldness similar to ours. Macaques are used to study minoxidil – a blood pressure drug that’s used – with some success – to treat male baldness.
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