Most male mammals have their penises covered in keratin spines, similar to nails, which they use to discard the sperm of other competitors and irritate the female to promote ovulation.
A study carried out by scientists from the universities of Stanford and Pennsylvania, in the United States, revealed in 2011 that this characteristic disappeared in man with a DNA fragment that was eliminated during our evolution. Researchers have also identified a region of the genome that has allowed our brain to expand, as published at the time in the journal Nature .
To reach this conclusion, the researchers, led by Gill Bejerano, started from the hypothesis that, instead of human DNA having advantages over that of the chimpanzee, “at some point in evolution we lost some chains of genetic information.” Thus they found 510 sections of missing code. They then chose the deleted regions of DNA related to male hormones, as well as brain development. They then introduced these code regions into mice to find out how they were expressed and found that they were responsible for the loss of sensory whiskers and penis spines , as well as brain growth.
Relationship with monogamy
Penis spines are common in other animals, including chimpanzees, macaques, and mice, but a more simplified morphology tends to be associated with the monogamous behavior of certain primates.
Many studies have tried to solve the question of what makes humans different from other organisms by looking for extra characteristics compared to those of the closest evolutionary relatives. This is the first time that specific human characteristics have been discovered by examining what has been lost throughout evolution.
The human penis
The human penis is anatomically divided into two areas: the glans and the root. The root of the penis begins directly below the bulbourethral glands with a long cylindrical body of tissue known as the corpus spongiosum. This tissue extends through the shaft of the penis to the tip, where it expands into a mushroom-shaped structure called the glans. Running through the center of the corpus spongiosum is the urethra, a common conduit for semen and urine; The urethra ends in a slit-shaped opening at the tip of the glans penis.
