I have need of this title again:
Oakland School's Lessons in Gender Diversity
Before I get to substance, may I ask where was the editor who allowed this title to get through without some capital letters? Oh, well, people who read news online probably write like that and wouldn't even notice. Actually, I didn't even notice until I wrote the title here. Anyway, on to something that actually matters...
Yes, fish can change gender (but not by will, there has to be a lack of the other sex before one changes).
I've never heard of geckos before, but there are apparently some species that are asexual. I guess to be a hermaphrodite (like an earthworm) you still have to find a mate, unlike aforesaid gecko. I'm an engineer, not a biologist. But I am a human and can definitely say that a human is not a bird, or a fish, or a fly, or a spider, or a gecko. A human is not of the same level of creation as the animals. And I'll believe that until a family of ducks moves to a new county to put their ducklings in a better school, or until an elephant writes to a publishing company to get printed the latest in his bestselling mystery novel series. Or until some reptiles get together hammers and brushes to dig up the bones of their ancestors. As human as we treat our dogs and cats (and though they've picked up human actions from us), no dog or cat is going to discuss with you their views on religion or politics. You can try to say that animals have souls, but it has just as much real world evidence as the Flat Earth Society.
What is a human, then? Why has marriage between one man and one woman been held up as the norm, and why has it been the only type of relationship that has survived for millenia? A human is made in God's image, and "God inscribed in the humanity of man and woman the vocation, and thus the capacity and responsibility of love and communion" (CCC 2331). It is the norm because that's how God made us. "Have you not read that from the beginning the Creator 'made them male and female; for this reason a man shall leave his father and mother and be joined to his wife, and the two shall become one flesh'"? (Mt 19:4f). CCC Article 6 (or 2331-2400) is a very complete explanation of human sexuality. I will end with 2393: "By creating the human being man and woman, God gives personal dignity equally to the one and the other. Each of them, man and woman, should acknowledge and accept his sexual identity."