Many men dream of having a larger member, and penis envy is at the root of much popular psychology - witness all those unwanted e-mails. But the idea of having a penis so large that it is an encumbrance is horrific. Penis length in humans generally varies from 10-20cm (erect), but there is a tribe in Africa in which the male member is much longer, and its owners tie it into a loose knot while walking. But for these people, it is big, but not quite an encumbrance.
Among animals, penises show a startling variation in both size, shape and number. Some flatworms have dozens of penises - essential because, in the competition over mates (which is complex because they are all hermaphrodites), individuals bite off each others' penises at every opportunity. The record for size must go to another hermaphroditic beast, the Corsican slug, whose fully extended member is 60cm long, four times longer than its body. The human equivalent would be an 8m-long penis.
