Common or not?

If these "alternative" genders and sexualities in the animal world are so common, then why is it that I've never heard of them before?

It used to be that people would argue about same-sex marriage with me saying that "it wasn't natural" and I would bring up a few famous cases of animal homosexuality (Ray and Silo especially, two male penguins that raised a chick). Then last year there was a New York Times article with a whole slew of cases  about gay animals. And now this book? Where was this book when I needed it? The new edition was published in 2009, but the first edition was published in 2004. I'm sure if my parents read this book (or just  the small section they were assigned) they would learn things that might change their view of the world. Ditto for the shy, closeted kids I knew back in high school. So is this just not widely advertised, or does everyone else in the world have some knowledge of this? To generalize... do we learn about these categories of gender and sexuality over time (1900s vs now) or do they become more specific over age (our personal lifespan, 12 yrs old vs. 20 yrs old)? For instance, am I learning about the things in this book because I am older and will be able to "understand" them better, or is it because we are living in an advanced age and this is new information?

Do we generalize too much with the terms "male" and "female" simply because we don't know enough yet (due to society or to personal learning)? This problem of not knowing enough makes me feel as if I am unqualified to make [temporary] opinions because they will probably change with the more I know. Why should I have the right to make opinions that could be wrong and with their wrongness could influence others to have wrong opinions about the world? I guess my worries will disappear when we become cyborgs with immediate access to all the information in the world..