A flashy new biotech startup launched yesterday called Colossal is on a mission to make an elephant-woolly mammoth mashup — with the ultimate goal of promoting biodiversity and combating climate change, it says. The effort has gotten a lot of hype and big-name backers, but scientists who work in conservation are still pretty skeptical. The science behind Colossal is in very early stages and is mired in ethical quandaries. The company won’t actually bring back a woolly mammoth, which hasn’t