Baldness is a genetically-inherited trait. 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.
But it’s possible that baldness might have had some reproductive rewards for our human ancestors. When lifespans were much shorter, baldness might have been a sign that a man had been strong and healthy enough to reach an advanced age, and would thus be a fit mate. Male pattern baldness – also known as alopecia – is indeed associated with high levels of male hormones.
Early human females also may have favored bald mates because it may have been easier to make sure they weren’t infested with parasites. Early humans were plagued by parasites such as lice and fleas, and a clean, bald pate may have been a signal of good health to a potential mate.
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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