Praise then darkness, and creation unfinished

I was reading rozk's journal, and came across the line "when I was twelve and still male" and, knowing what that meant, still had the thought of a species that changed gender as they age, and started wondering what it would be like if some people changed earlier than others.

I think I've figured out my problem with a lot of the sf that talks about the "Singularity", and doubly so with the people who take it as a real-life given: evolution isn't that directional or predetermined. I can certainly accept the idea that people--or some people--may move in that direction. What I can't buy is the idea that this must happen, that it's as inevitable as entropy, or that if some people decide they'd rather be uploaded software, that will eliminate humans as a species of animal living on the planet in physical bodies.