Asked by: Chris Saunders, Colchester
The sensitive response to androgen – a sex hormone – is an important feature of human hair. At puberty, hair grows in places where we had none; and as we age, changes in hormonal levels can lead to thinning hair in both men and women, and to baldness in some. But humans are not the only animals to experience this. It happens in chimps and stump-tailed macaques in nearly the same way. And mice, rats, hamsters, rabbits and sheep became sensitive to fur loss when their androgen levels were manipulated in the laboratory. There was even a report in which wattled starlings in the wild displayed a bald scalp in response to natural changes in androgen levels.