Publication highlights

Researchers at the Francis Crick Institute and Heidelberg University in Germany have shown that sex differences in animals vary dramatically across species, organs and developmental stages, and evolve quickly at the gene level but slowly at the cell type level. The researchers analysed the activity of genes in males and females over time in humans and four species (mice, rats, rabbits, opossums and chickens), covering the development of five organs (brain, cerebellum, heart, kidney and liver), into adulthood in the animals and up to birth in humans.

They discovered that organs which are different between the sexes vary across species, and in all animals and humans, few sex differences occurred while organs were developing, instead increasing sharply around sexual maturity. Only a very small number of sex-biased genes were shared across species, suggesting that sex differences have evolved quickly, but the same type of cells are sexually dimorphic across species.