Parasite Evolution: Here's How Some Animals Became Moochers

Nobody likes a mooch, but new research finds that grifting off others is a sound evolutionary strategy. Parasitism — a survival strategy that involves hijacking a host's nutrients for one's own benefit — has emerged in the animal kingdom at least 223 times, according to a study published July 19 in the journal Biology Letters. The estimate of 223 independent origins of parasitism is nearly four times higher than the previous estimate of around 60.