An anonymous reader writes "A centuries-old religious ceremony of an indigenous people in southern Mexico has led to evolutionary changes in a local species of fish, say researchers at Texas A&M University. Apparently since before Columbus arrived, the Zoque people would venture each spring into the sulfuric cave Cueva del Azufre to beg the gods for bountiful rain. As part of the ritual, they released into the cave's waters a leaf-bound paste made of lime and the ground-up root of the barbasco plant, a natural fish toxin. The rest is worth reading, but the upshot is that the fish living in the cave waters eventually got wise, genetically speaking."
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