Where does the penis come from? How originated? A team of researchers from the Harvard University School of Medicine (USA) has solved this enigma where nature has a lot of variety. The work has been published in the journal Nature .
This part of the reproductive system is, or rather was, the great unknown regarding how the external genitalia allowed vertebrate animals to reproduce . The truth is that there are tangible differences: humans and birds have a genital organ, however, snakes or lizards have two hemipenes. However, their structures work in a very similar way. Whether they are chicken, lizard, mouse or snake genitalia, they all have an equivalent tissue structure. ” The difference between the genitalia seems to be a second tissue that sends signals that order neighboring cells to create external genitalia “, clarifies Clifford Tabin, leader of the study.
According to scientists in chick embryos, the cloaca (an organ at the end of the digestive tract where the urinary and reproductive tract meet) emits molecular signals for neighboring cells to form the external genitalia. It is therefore the location of the cloaca that determines which tissues receive the first signal. In mammals, the penile-creating tissue is closer to the tail and in snakes and lizards, closer to the lateral mesoderm.
The researchers confirmed this finding with two groups of chicken embryos . The first group was grafted cloacal tissue next to the limbs, and the second group next to the tail buds. The results revealed that cells closest to the grafted cloaca responded to the signals and partially became genitalia, as they hoped to confirm.
“In a broader sense, the importance lies in the concept of evolution by ‘homology’ . A structure found in two different organisms is homologous if the structure was inherited from a common ancestor who had a version of that structure. Thus, the wing of a bat, the fin of a whale and the hand are homologous, all derived from the same forelimb of a common ancestor ”, explains Tabin.
