Exactly. Heterosexuality is the norm within the Animal Kingdom. It is so by necessity.
It just so happens that Biblical advice regarding sexuality is in accord with the natural order, too. In nature, there is often competition to mate. The Bible establishes an order where each male and female pair is protected and celebrated by society. A strong, intact biological pair produces best results for society as it creates the next generation. This is why government should be in the business of promoting morality as a moral population produces best results for all.
It’s definitely the norm but other things happen in in the Animal Kingdom. Evolutionists believe incidence of homosexuality is to reduce competition for mates while still providing adults to protect the group. If everyone is an alpha no one survives. We know prison populations will turn to available same sex outlets and drunkenness will lead to behaviors too even among flies.