I want to answer a few questions and in the process raise others – why did males have penile spines? Why are those spines no longer part of human penis?
After studying human genomes, and comparing it to the genomes of chimpanzees and macaques, scientists have discovered that DNA sequences thought to play a role in the production of penile spines have been deleted in humans, but has been preserved in other primates. In their research, scientists identified 510 stretches of DNA that have been conserved in our primate relatives but deleted in humans.
Penile spines are barb-like structures found in many mammals. It is believed that these ’spines’ enhance stimulation for the male during mating. However, there are suggestions that these spines might have evolved to remove “mating plugs”. These plugs enabled males to deposit material or seal female genital tract in order to block rival males attempting to engage in copulation with their mates. This is where the penile spines come in handy, since it allows penetration and thereby fertilisation.
Due to the danger these penile spines and plugs cause to the female genitals, scientists are assuming the females themselves forced change in human male courting behaviour. According to scientists, females sought caring mates and rejected violent mates who plugged up their genitals. This change wasn’t without consequences though – loss of penile spine reduced sensitivity, longer copulation and 70% weaker orgasms.