Scientist reveals the surprising reason why human penises are so big
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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.
![[The average human male has a large phallus, in comparison with some of our closest living relatives. While the average 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). Pictured, a male chimp]](https://i.dailymail.co.uk/1s/2025/01/17/15/94214147-14283707-image-a-12_1737127265293.jpg)
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.
![[Human testicles are 'rather small' when compared to other living primates such as the bonobo and the chimp. This image shows male and female great ape sexual organs, compared for size (bonobos are flat chested until they get pregnant)]](https://i.dailymail.co.uk/1s/2025/01/17/15/94215249-14283707-image-a-13_1737129223875.jpg)
'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,' he told MailOnline. If you're ever unsatisfied with the size of your penis, it may be comforting to know that it's actually pretty big - at least relatively speaking (file photo).
![[Mark Maslin, professor of palaeoclimatology at University College London, says the human penis is 'extremely dull' relatively speaking. This image shows more complex primate penises - brown lemur (a), white-bellied spider monkey (b), black-capped squirrel monkey (c), macaque (d, e, f), baboon (g) and chimp (h)]](https://i.dailymail.co.uk/1s/2025/01/17/16/94215245-14283707-image-a-17_1737129987897.jpg)
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.
