A recent discovery has shed light on the surprising reason behind the size of human penises compared to other primates. According to biologist Simon Underdown, professor of biological anthropology at Oxford Brookes University, humans’ relatively large penises are a result of their evolutionary shift from quadrupedalism to bipedalism.
Underdown suggests that as humans began walking on two legs around 2 million years ago, it became more difficult for semen to reach the cervix during copulation. To compensate for this issue, the human penis evolved to become larger. In contrast, chimpanzees and bonobos, who remained quadrupedal, have smaller penises.
The theory is based on a widely accepted understanding of the differences between humans and chimps as a result of bipedalism. Underdown’s findings also highlight the unique characteristics of human testicles, which are relatively small compared to other primates. Interestingly, chimpanzees have evolved massive testicles to produce large amounts of sperm, often resulting in multiple fertilizations.
The discovery provides insight into the evolutionary pressures that shaped human reproductive anatomy, and how our species’ unique traits, such as bipedalism, have influenced our biological characteristics.
Source: https://www.dailymail.co.uk/sciencetech/article-14283707/Scientist-reason-human-penises-big.html