Animal Self-Medication

Nice article in the Times reviewing the research in animal self-medication that I have mentioned here before. I learned from it that sheep self-medicate to control intestinal parasites, switching their diets to include more bitter or tannin-rich plants when their parasite load is high. This is fascinating:

The abiding question — the greatest puzzle of all, really — is how animals first learn which plants are medicinal. Villalba has observed that lambs infected with parasites are more likely to try new plants when grazing in an open pasture compared to uninfected lambs. They lose some of what scientists call food “neophobia,” the fear of new flavors, and their greater willingness to explore the surrounding foodscape may increase the odds of a medicinal discovery.

Huffman calls these tendencies “pre-adaptations.” They’re hard-wired behaviors that push animals toward the acquisition of medical knowledge — in this case, by impelling them to try the very flavors they normally shun. Arguably, this exploratory behavior exhibits a fundamental insight about the world, which, fully articulated, might go like this: Plants have evolved an exquisite array of poisons and noxious compounds to protect themselves. Many of these are directed at invertebrates and microbes, relatives of what makes an animal sick. So a terrible-tasting plant, one usually avoided, has a better-than-average chance of beating back whatever is making that creature ill.

And here's a good example of a very common type of story told by traditional shamans about how they acquired their own medical knowledge:

Huffman often tells a story he heard from his friend Kalunde, who died in 2013, to illustrate the point. Kalunde’s grandfather, a healer, once watched a sick porcupine eat the roots of a plant known to be quite poisonous. When the porcupine recovered, Kalunde’s grandfather began experimenting with the root in small doses, first on himself and then on fellow villagers. It turned out to be an effective treatment for dysentery, one the Tongwe still use today.

In case you ever wondered why traditional human medicine involved so much purging and so many enemas, remember that intestinal parasites used to be one of the main causes of our medical problems. This line of thinking also explains our old belief that effective medicine should taste terrible.