How mammary glands appeared in the course of evolution

A team of geneticists demonstrated that the emergence of mammary glands in placental mammals and marsupials results from recycling certain ‘architect’ genes. The latter, known as Hox genes, are responsible for coordinating the formation of the organs and limbs during the embryonic stage. Such genes are controlled by complex regulatory networks. In the course of evolution, parts of these networks were reused to produce different functions. Architect genes were thus requisitioned to form the mammary bud and, later, for gestation.