BOB HIRSHON (host):
Human-induced evolution…I’m Bob Hirshon and this is Science Update.
For centuries, the indigenous Zoque people of sourthern Mexico performed a religious ritual inside a cave. They put a toxic paste made from the barbasco plant into a river running through the cave, and then implored their deities to bring rain for a bountiful harvest. A species of fish called the Atlantic molly lives inside the cave. The barbasco paste sedated the fish, and the people then captured them to feed their families. But Oklahoma State University evolutionary ecologist Michael Tobler says that says over the years, the fish became less sensitive to the toxin.
MICHAEL TOBLER (Oklahoma State University):
When we exposed fish that have historical experience, they can last much longer in toxic water than fish that were never exposed to barbasco.
This suggests that the cave fish have evolved genetic resistance to the toxin in response to the annual ritual. I’m Bob Hirshon, for AAAS, the science society.