It's not as if environmentalists really need something new to worry about. The planet's temperature is set to rise four or five degrees-every glacial system is already in rapid retreat, and icebergs measured in units of U.S. states (the size of Rhode Island!) are calving off the Antarctic. Species disappear daily; acid rain; and you know the whole damn litany. We could be forgiven for wanting to take a pass on human genetic engineering.
And yet I think it may turn into the single greatest battle environmentalists have ever fought, the one for which the Grand Canyon and the African elephants and Amazon deforestation and Love Canal were preparing us. The real test.
Some of the reasons for thinking so are pragmatic. Changing the human germline is an almost preposterous override of the precautionary principle, the idea that if you don't know something's safe you shouldn't do it. We have rushed with blinding speed through the first phases of the biotechnological revolution-what was experimental a decade ago now grows in half the corn and soybean fields...