CBC Radio’s Quirks and Quarks interviewed Dr. Gerald Callahan, author of Between XX and XY: Intersexuality and the Myth of Two Sexes.
“When I began looking into it I discovered that the biochemistry and genetics that underlie the process of sex development in a fetus are very complex events, and in fact imagining they will turn out just one of two ways is really not very thoughtful. For example: I think the processes that generate sex in human beings are at least as complicated as those that generate fingerprints, and almost every one of us has a unique set of fingerprints. I began to realize that thinking of this like the on/off switch on a radio wasn’t the right way to think of it, that it’s more like bass and treble. You know the pure bass and pure treble are unachievable, but there’s a million different possibilities in between.” - Dr. Gerald Callahan
The show is available as a podcast.