Biologist Todd Schlenke became fascinated with how fruit flies protect themselves from a parasitic wasp: the flies drink alcohol, a toxin that they can withstand more than the wasps can:
If the flies could drink alcohol to kill their parasites, it would suggest that maybe the same thing might apply to humans. … These flies, who drink for a living, drink more in order to stay parasite free, even if it makes them a little sick. They drink more when parasites are more of a problem. They drink more, in other words, in situations like those encountered by the first settlements of humans, situations in which parasites are common.