People have been getting rid of cockroaches for decades by setting out bait mixed with poison. But in the late 1980s, in an apartment test kitchen in Florida, something went very wrong. A killer product stopped working. Cockroach populations there kept rising. Mystified researchers tested and discarded theory after theory until they finally hit on the explanation: In a remarkably rapid display of evolution at work, many of the cockroaches had lost their sweet tooth, rejecting the corn syrup meant to attract them.