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Some mammals - the raccoon for example - have a penis bone, whereas other mammals - such as humans - don鈥檛. So why is it in some animals but not in others? Matilda Brindle and Kit Opie of University College London asked this exact question and have recently published their findings. Results of their study suggest that the evolution of the penis bone is associated with the both the duration of sexual intercourse and the amount of sexual competition between males.

Picture: Over 80% of all mammals have a penis bone and they come in a vast array of shapes, 漏 91热爆