BIOLOGICAL SEX is an important adaptive function for a vast number of plant and animal species. The recombination of genes during sexual reproduction allows fast adaptation by producing a kaleidoscope of new possibilities. Species that use sexual reproduction have sex gametes which divide up and recombine genes from each parent to produce a new organism.

Many species of plants and animals are also hermaphroditic. This means a single organism has both male and female sex cells, allowing for self-fertilisation where sexual reproduction does not require another organism. Other species convert between different sexes depending on their age, the sex of their peers, or their environment. Other species do not have different sexes at all.

The observation of nature is a fascinating resource to draw on when understanding ourselves as animals. We can observe both similarity and difference between ourselves and other organisms, whatever they are, as a function of our imagination and capacity to think through analogy.