The research, reported in the journal Nature, helps explain the genesis of external genitalia. It turns out that reptile and mammal genitalia have at least some things in common.
The researchers found that the development of limbs and external genitalia are linked. In snakes and lizards, the external genitalia are made from the same tissue from which the reptile’s hind limbs (or remnants, as with snakes) originate.
In mammals, on the other hand, they are made from what’s known as “tail-bud” tissue. This is a knob of embryonic tissue that contributes to the formation of the posterior part of our and other mammals’ bodies.
"While mammal and reptile genitalia are not homologous in that they are derived from different tissue, they do share a 'deep homology' in that they are derived from the same genetic program and induced by the same ancestral set of molecular signals," lead author Clifford Tabin said in a press release.
Tabin, a professor at Harvard Medical School's Department of Genetics, and his team examined how genitalia first develop in the embryos of certain animals, including snakes and chickens.
Before the genitalia emerge, the embryonic cloaca (tissue that eventually develops into the urinary and gut tracts) issues molecular signals that tell neighboring cells and tissues to form into external genitalia. The researchers discovered that the cloaca's location determines which tissues receive the signal first.
Read more at Discovery News
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