How humans lost penile spine?
Many people know that human males don’t have spine in their penises. But most people don’t know that males in Chimpanzees and other mammals have penile spine. Now scientists from Stanford University discovered a stretch of DNA shared in mammals but not in humans that can explain the lost of human penile spine. Their paper is published today in Nature.
The DNA stretch covered an enhancer near a gene encoding Androgen receptor, androgen is one of the most important hormones that induces the development of our sexualities. Moreover, other studies have proved that the development of penile spine is androgen dependent. Therefore, this team of Standford scientists investigated the function of this enhancer by putting it in the mouse embryo with a reporter gene. They found that this piece of DNA governs the expression of reporter gene in two regions of mouse embryo: facial vibrissae and genital tubercle. With this result, they speculated that humans lost facial vibrissae and penile spine because of the deletion of this very piece of DNA.
In the end, the authors also speculated that the lost of spine decreases the tactile sensitivity of penis and increase the duration of sexual intercourse in humans, which strengthen the pair-bonding and parental care, which in turn increase the evolutionary success of our species.
Reference:
Human-specific loss of regulatory DNA and the evolution of human-specific traits
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