by Denyse O'Leary
No, this isn't about what you think. For once, we are talking about frogs and newts.
A friend notes that an evolutionary biologist puzzles as follows:
"One of the most puzzling paradoxes in the evolution of toxins is why organisms evolve to be deadly - contrary to venoms, for which deadly effects have a clear benefit. Extreme toxicity occurs repeatedly, from saturniid caterpillars to dart poison frogs. Selection favors the most-fit individuals, and those should be the ones that avoid predation. Killing an individual predator does not give an advantage over simply deterring one, especially if the prey has to be handled or eaten by a predator to deliver the poison. How, then, can we explain the evolution of deadly toxicity?" (Brodie, E. D., III. 2009. Toxins and venoms. Current Biology 19: R931-R935.)
Brodie, I'm told, is a leading researcher on evolutionary arms races at the University of Virginia. He goes on to suggest a solution: "arms races between predators and prey ... drive the exaggerated evolution of toxicity in general, without resulting in deadly consequences to the primary selective agent." (R933) He suggests as an example is the predator-prey relationship between garter snakes and a newt that produces tetrodotoxin powerful enough to kill 10-20 humans or thousands of mice. But the interesting thing is that the snakes, which seem to be the "primary selective agent" for newts, in the sense of selecting them for dinner, are resistant to the toxin. Brodie attributes the newts' heightened toxicity to coevolution with the garter snakes.
My friend asks, "But how does that solve the paradox? Newts with a higher level of toxicity would only accrue selective advantage if those higher levels of toxicity protected them against the predators."
Well, I suspect the answer lies in another question: What do we think the problem is, exactly? For a Darwinist, the goal is to persuade others that natural selection is the primary source of new information in the history of life. Therefore, the problem is "coming up with a Darwinian explanation", however unsatisfactory it is. And my friend should know by now not to ask any questions if he really needs his job. (See Expelled.) Shut up, Brodie explained.
Of course, a non-Darwinist like myself would hazard a guess that no selection whatever is involved (because I don't need selection to do anything in particular and am not looking for it when it probably isn't there). If neither predator nor prey are affected by the prey's toxicity to life forms that are irrelevant to their mutual ecology (such as humans), there is no reason the prey shouldn't have as high a level of toxicity as is chemically consistent with its continued life. And for all we know, the toxin provides some hitherto unlooked for convenience for the newt.
Besides which, anyone who tried to research this topic up close and personal in the wild may now be referred to exclusively in the past tense ... Jane Goodall lives on another street, I am afraid.
Denyse O'Leary is co-author of The Spiritual Brain.
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