Pixar’s Finding Nemo told of a touching bond between a clownfish father and son. But according to this fascinating excerpt from Stephen R. Palumbi and Anthony R. Palumbi’s new book The Extreme Life of the Sea , Finding Nemo director Andrew Stanton bypassed the most intriguing trait of clownfish, which is that they can change their sex. Had Pixar stayed true to clownfish biology, they would have ended up with a quite different story:

The 2003 Disney film Finding Nemo formally canonized the anemone dweller’s adorability. The eponymous clownfish vanishes from his home anemone, forcing his widowed father to take off after him. Finding Nemo gets many things right—the anxiety of leaving home and the obnoxious yelping of seagulls—but it punts away the most fascinating aspect of clownfish. As sequential hermaphrodites, they lead unique home lives. All are born male, with the ability to change sex. Like a wild card, it’s only good once: once males turn into females, they can’t turn back into males. The film supposes a lifelong romance for Nemo’s parents, but genuine clownfish live only as part of larger groups. A handful of fish share each anemone, all beginning their lives as immature males. The largest and most dominant male turns into a female; the next-largest develops functioning testes. She lays eggs, he fertilizes them. The others bide their time, defending the anemone and the family’s precious eggs. One of the mated pair will eventually die, to be swiftly replaced by someone down the ladder.

If the matriarch dies, the fertile male who was #2 now takes her place as #1, metamorphosing into a female himself. A simply hierarchy of size and strength determines the family’s whole structure, conflicting with the acceptable social norms for children’s movies. Finding Nemo painted a simple picture for more than just the sake of simplicity: a real clownfish father who lost his mate would not develop a psychologically complex system of grieving and overprotection. He would simply become Nemo’s new mother. Nemo (the only other fish remaining in the anemone) would rapidly develop mature gonads. He would become his own father while his father became his mother, and they would raise little incestuous Nemos together without a drip of sentimentality. In retrospect, the producers at Disney probably made the right call.