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Cane toads: At a certain point, “evolution” becomes an excuse for not thinking clearly


At Nature: “Study finds that the noxious pests have become so numerous, they’ve developed a taste for each other — as well as defences to ward off such attacks”:

The discovery could help researchers to understand the evolutionary underpinnings of how this uncommon and extreme behaviour emerges. Scientists have seen cannibalism evolve in species before, says Volker Rudolf, a community ecologist at Rice University in Texas, who studies the phenomenon. But what’s exciting about this work, he says, is that the researchers are almost seeing it “develop in front of their eyes”, given that the behaviour arose in less than a hundred years — the blink of an eye by evolutionary standards…

Although adult cane toads are fearsome — they grow up to 25 centimetres in length — it’s their tadpoles that are usually the cannibals. Multiple tadpoles together can gobble more than 99% of the hatchlings that emerge from the tens of thousands of eggs in a single clutch.

Max Kozlov, “Australia’s cane toads evolved as cannibals with frightening speed” at Nature (August 25, 2021)

And this is some kind of a find or any kind of a problem because… ?

Basically, the invasive cane toads, with no natural enemies in Australia, have taken to eating each other. What “evolutionary underpinnings” do we require to understand that?

The toad has no mind, no morals, no overarching concerns. It needs to fill its maw with something and why not another cane toad? “You today, me tomorrow!”

And of course they develop defenses to ward off such attacks; otherwise, the younger offspring would all be eaten. But the toad doesn’t know that or care.

In fact, the toads are a good example of overarching laws of nature that regulate things and keep them in balance. But just watch Darwinians try to get window dressing for their schoolbook-enforced theory out of it:

Roshan Vijendravarma, an evolutionary biologist at the Curie Institute in Paris, who has studied cannibalism in fruit flies, says the differences between the invasive and native toads’ behaviour probably have a genetic basis, given how extreme they are and how quickly they evolved over relatively few generations of toads.

Shine and his colleagues think this idea is worth exploring and are studying it now. Although there are still mysteries around the cane toads’ cannibalistic tendencies, one thing is for certain, says Shine: “The cane toads that are currently hopping across Australia are extraordinarily different animals from the ones that were first taken out of the native range.” Max Kozlov, “Australia’s cane toads evolved as cannibals with frightening speed” at Nature (August 25, 2021)

Genetic basis? It sounds like a flaw designed into the system by inescapable laws: Being omnivorous, they start eating each other.

It’s not clear how different the current lot is from their recent ancestors. More likely, they just ran out of other things to eat and turned to younger hatchlings. It’s one of the things that can happen when a life form becomes a mere eating machine:

Indeed, the toads didn’t “slow down,” as noted in the narrative of this 2010 clip. Instead, they started eating each other. Whoever did the calculations for toads had that right.

File under: Why doesn’t all life just die out? Current best answer: Because Whoever did the calculations had thought about the contingencies.

This seems more like a case of devolution. In their normal habitat, the toads had to be wary of predators, and perhaps had some built-in (genetic?) mechanism to avoid eating each other in order for the population to be maintained. Once introduced into Australia, however, the lack of predators, and wide open expansion room, meant that certain genetic traits - e.g. the discouragement from eating your buddies - were no longer needed, so at some point that gene was damaged (mutated to become inactive) so that the un-discouraged offspring got to eat more, thereby out-competing the others - a major survival benefit! This damaged gene then spread quickly through the population (strongly selected). If this trait had appeared in the normal environment, so that the mutated tadpole ate all of its buddies, it would then be alone and either more likely to be eaten by its normal predators, or else unable to find a mate in a sparse population. Either way, the mutation would not have been beneficial in the normal environment and thus, would not have been naturally selected. If this is the case - and only comparative genome studies could tell - then this is a clear example of Michael Behe's thesis, that the usual and easiest way for Darwinian evolution to proceed is by damaging or blocking something that, in that particular situation, benefits the species; i.e. loss of genetic info or function, AKA devolution. One wonders whether the mutated Aussie toads would survive and multiply if returned to their natural habitat? Or would their propensity to eat their brethren doom them to extinction? Fasteddious

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