The sexual imperative. Part 5, The young ones.

The Sexual Imperative series explores the reasons for sexual and asexual reproduction in the insect, animal and human worlds. This episode looks at how parents provide for their young. For animals with large brains, the parents must teach the young about how to survive. Chimpanzees, orang-utans and humans do this for many years. Other parent animals provide for their young by giving them a good chance of survival; squid lay thousands of fertilised eggs on the seafloor, ensuring that some will grow to adulthood. The jewel wasp paralyses a cockroach and lays its egg on it, thereby providing a source of food. Different food sources provided by parents are shown: the South American discus fish exudes a nutritious slime that the young feed from; bulldog ants lay trophic ants to feed larvae; honeybees feed larvae pollen and honey or royal jelly. Examples of marsupials are shown; the bandicoot feeds its embryonic young with nipples in its pouch, and of placental mammals, such as elephants, which stay in the womb for almost two years and suckle for up to five. Many human cultures have a kind of coming-of-age ceremony, which marks the end of the parents' reproductive process.