Mexicans make fish evolve, according to New Scientist, 14 September 2010 and Biology Letters online 8 Sept 2010 doi: 10.1098/rsbl.2010.0663. In an article entitled “Religious rite gives evolution a helping hand”, New Scientist claims that the Zoque people of southern Mexico are causing fish in a sulphurous cave named Cueva del Azufre to evolve. The Zoque people stun the fish with the mashed root of the Barbasco plant, as part of a ritual to ask their gods for rain. The root contains a powerful anaesthetic and a research team led by Mark Tobler of Texas A and M University have studied the effects of it on fish from the cave and on fish of the same species from upstream. They found “Barbasco tolerance increases with body size and differs between the sexes. Furthermore, fish from sites exposed to the ceremony had a significantly higher tolerance.” According to New Scientist these results suggest “over time, evolution has selected fish that can cope with the toxin.” Tobler commented: “The study indicates that the fish have adapted to the local Zoque traditions.”

Editorial Comment:T he difference between the two groups of fish has involved selection, but it is not evolution, or even adaptation. In the cave, fish that were originally most sensitive to the Barbasco plant have been killed off, leaving only fish that were already less sensitive to survive and breed. It is not adaptation because the surviving fish already had tolerance to the anaesthetic. They did not change. The fish are still the same species and have not changed into any other species. Therefore, there is no evolution either. This article reminds us to be discerning about the use of the words evolution and adaptation and other catchphrases used to promote evolution. (Ref. ichthyology, toxins)

Evidence News 22 September 2010