Ubudoda bomuntu buyahluka ngosayizi ezinyathelweni eziningana, kufaka phakathi ubude nobubanzi lapho i-flaccid futhi imile.Ngaphandle kokwehluka kwemvelo kokuthomba komuntu ngokujwayelekile, kunezinto eziholela ekwehlukaneni okuncane kowesilisa othile, njengezinga lokuvuka, isikhathi sosuku, izinga lokushisa ekamelweni, izinga lokukhathazeka, umsebenzi wezemidlalo nobuningi bezenzo zocansi.Uma kuqhathaniswa namanye ama-primates, kufaka phakathi izibonelo ezinkulu njenge-gorilla, ipipi lomuntu likhulu kakhulu, zombili ngamagama aphelele futhi lihlobene nawo wonke umzimba. Nakuba imiphumela ihluke kancane yonkana izifundo elihle, abavumelana ukuthi kusho womuntu umthondo, lapho uqonde, ungaphakathi uhla ngobude.