November 5, 2010
COLLEGE STATION, Nov. 4, 2010 — A centuries-old religious ceremony of an indigenous people in southern Mexico has led to small evolutionary changes in a local species of fish, according to researchers from Texas A&M University.
Since before the arrival of Christopher Columbus to the New World, the Zoque people of southern Mexico would venture each year during the Easter season deep into the sulfuric cave Cueva del Azufre to implore their deities for a bountiful rain season. As part of the annual ritual, they release into the cave’s waters a distinctive, leaf-bound paste made of lime and the ground-up root of the barbasco plant, a natural fish toxin. Believing the cave’s fish to be gifts from their gods, they scoop up their poisoned prey to feed upon until their crops are ready to harvest.
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They found that the mollies annually exposed to the barbasco indeed were more resistant than the fish further upstream — to the extent that they were able to swim in the noxious water nearly 50 percent longer. Tobler and Rosenthal’s group concluded that human beings had, over time, not only affected molly population dynamics, but also inadvertently kick-started the evolutionary process of natural selection as well. Mollies able to tolerate the poisonous conditions survived and passed those traits to their offspring, resigning those that perished to their fate of serving as a ceremonial feast for the Zoque.
http://scienceblog.com/39940/moved-by-religion-mexican-cavefish-develop-resistance-to-toxin/