Male – female. Man – woman. Mother – father. Simple, right?
Maybe not. In nature, gender is fluid, roles can be reversed, and homosexual behaviour is common. As they say on social media, “it’s complicated”.
By exploring the natural world, we challenge the widespread view that men are men, women are women, mothers are the child-rearers and gender is fixed at birth.
One common idea is that females look after the young and males are there just to fertilise their eggs. Yet many birds don’t fit this family structure. Male cassowaries guard the nest once the female has laid the eggs, and then raise the chicks as a single father. Seahorses are famous for their males being ‘pregnant’ and, in mammals, the Topi antelope reverses the “normal” male-female mating pattern. The females only come into estrous one day a year. They’re so desperate to mate, they must compete for the best males and the females fight each other.
But surely gender is fixed at birth? Not necessarily. There are many cases where an animal changes sex during its life. Made famous by Finding Nemo, clownfish live in small groups on their sea anemone. The biggest fish is the breeding female and the next biggest is the breeding male. If the female dies, the breeding male changes sex and becomes the breeding female; the next biggest fish becomes the breeding male. All clownfish are born male and only become female when they become the dominant fish on their anemone.
And the great taboo – homosexual behaviour? Again, contrary to common belief, this occurs across a huge range of species from insects and starfish to birds (500 species have homosexual behaviour that we know of) and primates such as bonobos – both males and females. It may even be important for practising courtship where two males court each other. Same sex penguin pairs are not rare although the sexes look the same, so it can be hard to tell, but other birds form long-term homosexual bonds – eg in graylag geese, 20% of bonded birds are homosexual and will raise chicks as their own if they find any in need of adoption.
Homosexual behaviour likely evolved very early in evolution and is one of the most ancient behaviours – an integral part of the evolution of life. As soon as sex evolved, animals just mated indiscriminately with either sex – ‘cheaper’ than evolving complex ways to distinguish the sexes – that came later. It’s not really aberrant behaviour at all – nothing could be more natural.