Articles on sex development

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Men have nipples because of a quirk in how embryos develop. But that’s only part of the story of this seemingly redundant body part. from www.shutterstock.com

Why do men have nipples?

How embryos develop, evolution and sexual pleasure all help explain why men have nipples. But ‘man boobs’ are a different story.
Chicken or rooster? This bird is both – female on the left (dark feathers), and male on the right (white feathers, with larger comb and physique). Mike Clinton (Roslin Institute)

How birds become male or female, and occasionally both

Birds have some of the most amazing sex differences of any animal. They can control the sex of offspring, and even produce rare half-male, half-females. And their sex genes and chromosomes are quite different from ours.
Many babies are born with a genetic variant that leads to ambiguous sexual development. .gsr./Flickr

Boy, girl or …? Dilemmas when sex development goes awry

Many babies are born with a genetic variant that can result in the child being neither a typical boy or girl. There has been considerable debate about whether the child should be treated.

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