Origin of dogs: different in reptiles and mammals, but similar

Python embryo with six days in the first two photos and 11 days in the last. In the latter, in the middle of the spiral of the tail is perceived the germ of the sexual organs and the bestigo of the legs. <

The genetics of Harvard University have explained the evolutionary origin of the penis. According to the study published in the journal Nature, the development of external genitals is not the same in all terrestrial vertebrates. In fact, in most mammals, the cells that develop the penis come from embryonic cells that produce the tail, while in snakes and other reptiles the back legs are produced.

In experiments with chicken embryos, researchers have concluded that the position of the cloaca is key in the development of organs, depending on which the intestines, sex organs and urinary tract develop. It seems that in the embryonic phase, clloaca sends signals that cause cell routing and the development of one tissue or another. In mammals, the sewer is near the tail germ and in reptiles near the germ of the back legs.

Thus, they have shown that different cell populations are able to respond to the cloaca signal and develop their sexual organs.