Discover! >> Scientist Reveal The Surprising Reason Why Human Penises Are So Big Compared To Other Mammals

If you’re ever unsatisfied with the size of your penis, it may be comforting to know that it’s pretty big – that is, relatively speaking.

According to biologists, the average human male actually has a large phallus, at least in comparison with some of our closest living relatives.

While the average human manhood measures 5.1 inch (13cm) when erect, the chimp and the bonobo only boast a 3.1 inch (8cm) shaft.

Meanwhile, the orangutan’s member measures 3.3 inch (8.5cm) and the gorilla only has a tiddler – just 1.25 inch (3cm).

Now, a scientist reveals the surprising reason why we really are ‘king of the swingers’.

Simon Underdown, professor of biological anthropology at Oxford Brookes University, said it’s ‘almost certainly’ related to humans starting to walk on two legs.

Becoming ‘bipedal’ has made it more difficult for humans to get semen to the right spot for conception – i.e. further into the vagina and nearer the cervix – and as a result, we have evolved larger penises.

‘Chimps and other primates don’t need to be big because they’re not bipedal and hence getting things to the right location is not an issue,’

To fully understand why humans now have relatively large penises, we have to look back millions of years in the story of human evolution and the other great apes.

The last common ancestor shared by the modern humans (homo sapiens) and apes in the Pan genus (chimps and bonobos) lived an estimated 13 to 5 million years ago.

This common ancestor was quadrupedal – meaning it moved around on four legs.

But while chimps and bonobos stayed on four legs to get around – doing a sort of ‘knucklewalk’ – humans gradually evolved to walk on two legs.

Humans likely became bipedal to adapt to Africa’s savannah grasslands, free up the hands to use and carry tools, and to intimidate predators.

‘The selective pressure to walk on two legs was massive and sustained for millions of years,’ Professor Underdown told MailOnline.

But there’s been many ‘knock-on effects’ of becoming bipedal – one of which is that we gradually grew larger penises to improve sperm delivery, the theory goes.

Chimps and other mammals are used to sitting with bent legs, which on an anatomical level helps the successful delivery of sperm during copulation and thus didnt present a need for them to evolve bigger penises.