Neanderthals were pretty smart, and if we actively killed them off, then probably we did so in the same way that humans kill each other.

There's this idea of shifting baselines. It was coined by a guy named Jeremy Jackson. It's the idea that every generation takes what it sees, and says, "Okay, well, that's the norm."

We're talking really huge global-scale change, and I did not feel that I had the prescription for that kind of action, so I'm going to leave it to the reader.

People tend to focus on the here and now. The problem is that, once global warming is something that most people can feel in the course of their daily lives, it will be too late to prevent much larger, potentially catastrophic changes.

I don't think there are too many places left that humans haven't pretty thoroughly explored.

Somewhere in our DNA must lie the key mutation (or, more probably, mutations) that set us apart—the mutations that make us the sort of creature that could wipe out its nearest relative, then dig up its bones and reassemble its genome.

If you're a conservation biologist in many fields, you're seeing your study subject disappear. People are in the position where they're chronicling radical decline, and that is not a position that conservation biologists want to be in.