I have always wanted to see a woolly mammoth. From the time I first read about them up until, well, a few moments ago, I’ve fantasized about going back in time to see a herd shoving its way through an Ice Age snowstorm. Alas, it cannot be, even if George Church and a new company, Colossus, bend heaven and earth to make it happen.

Possibly as many as half of the coral reefs that existed 100 years ago have been destroyed, sometimes by removing them, covering them up, or blowing them up, but mostly...