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Do toads goad snake evolution?

David Catchpoole

18 April 2006

When leading public institutions repeatedly broadcast as fact that ‘we see evolution happening today’,1 it’s not surprising that many people believe it.

One example is a recent prime-time breakfast radio segment on Australia’s national broadcaster, ABC Radio National. The University of Sydney’s Professor Richard Shine told the presenter Fran Kelly that he and his co-researchers studying snakes have observed ‘genuine evolutionary changes’.2

What were they? Allegedly snakes are evolving to cope with the spread of cane toads across the Australian continent. (Cane toads were introduced to north Queensland in the 1930s, and have steadily expanded their range, moving south into New South Wales and west into the Northern Territory.) The changes are making snakes ‘much less vulnerable’ to the toxin in the toad’s skin. (One reason that the cane toad has spread so rapidly is its toxic gland that can kill native predators that eat it.)

But as the interview progressed, the discerning listener would have picked up from Professor Shine’s own words that he and his colleagues had not observed evolution at all. Rather, it was an example of natural selection acting to favour certain already-existing genetically determined traits in the snake populations. Creationists do not dispute natural selection—indeed it is an important part of the biblical creation/Fall/Flood/Dispersion model, and was theorized by creationists even before Darwin!

The researchers had firstly been able to rule out learned behaviour as a factor in this case. ‘We’ve done a bunch of trials to see if it could just be that the snakes are learning and so forth but they seem to be remarkably stupid …’, said Professor Shine, going on to emphasize the genetic basis to snake behaviour:

‘Basically you’ve got a strong genetic component to feeding responses, and some snakes really go mad on eating frogs and others really want to eat nothing but mammals and so forth, and it’s actually pretty sophisticated. And there’s a lot of work overseas showing that even within a single litter of baby snakes you’ve got genetic variation in what kinds of things they treat as prey. And it’s just that the only snakes that survive after the toads arrive are the ones that happen to be born with a set of genes saying: “If it looks and smells like a cane toad, don’t eat it.”’

And genetically-determined physical attributes such as the snake’s head dimensions and body size are key factors too.

‘Essentially the size of the toad you can eat depends on the size of your head, so if you’ve got a small head you can’t eat a very big toad.’

So, if you’re a snake, having a small head stops you eating big toads, which have more poison, therefore helps you to survive. And having a big body helps as well:

‘The size of toad it takes to kill you depends on the size of your body. So if you’ve got a really big body, it takes more poison. So, basically, the right shape to be when the toads arrive is to be a big snake with a small head and that’s exactly the evolutionary change that we’re seeing in a couple of species of snakes, through the history of the toad’s invasion in Queensland.’

But the toad-goaded natural selection favouring large-bodied, small-headed snakes and/or snakes with an apparently genetically-predetermined aversion to eating cane toads is not ‘evolutionary change’. To get from pond scum to snakes requires an increase in genetic information but all that Professor Shine and his colleagues have observed is a culling of genetic information. Genes that code for large heads, small bodies and an urge to swallow a cane toad are being removed from snake populations, no doubt reducing the afore-noted existing ‘genetic variation’. See also The evolution train’s a-comin’ (Sorry, a-goin’—in the wrong direction).

And you’d expect it to happen quickly—i.e. in just one generation you’d expect to see, in a population of snakes, an increase in the numbers of snakes with large bodies, small heads, and a decided lack of interest in hunting cane toads. But evolutionists, used to thinking that slow-and-gradual evolution is how we got here, and that change through natural selection is evolutionary, are often caught by surprise at the rapidity of such changes.

When ABC presenter Fran Kelly put it to Professor Shine that what he’d observed was ‘pretty quick for evolutionary changes, physical changes like this, isn’t it?’ Professor Shine responded:

‘Yes, look, I’m amazed at the speed that it’s all happening. I mean, we’re used to antibiotics eliciting very rapid change in microbes, and insects evolving to pesticides and so on, but these are pretty big vertebrates that take a couple of years to mature and so on. So you would have expected that evolutionary change would be fairly slow. But of course the toads are a massive selective force in evolutionary terms. The only way to make a living as a black snake, once the toads have arrived is to somehow have a trick that makes you invulnerable, and that seems to be exactly what’s happened.’

Toads are indeed a ‘massive selective force’, but not ‘in evolutionary terms’. The gene-coded ‘trick’ favouring snake survival when cane toads are present did not ‘evolve’ out of nowhere—it was already present in the snake population. But such is the ruling evolutionary paradigm that many people can’t (or won’t?) see this point. (A New Zealand atheistic evolutionist writing in Wellington’s main newspaper has likewise invoked this natural selection in Queensland toad-eating snakes as ‘proof’ of evolution in action; see CMI refutation published in the same paper.)

If only Professor Shine and his colleagues knew that the antibiotic-elicited rapid change in microbes (see also here and here) and pesticide’s selective culling of insects do not show any evidence of evolution either, it would put what they really observed in a whole new light, as was the case for the former evolutionist who gave his testimony on this DVD.

References

  1. This leaves Christians who say they accept evolution in an indefensible position, because (among other reasons) if the Creator used evolution, and evolution is happening today, then the Creation is not finished—in stark contrast to what Scripture says (Genesis 1:31–2:3; Exodus 20:11). Return to text.
  2. Snakes vs toads—Fran Kelly interviews Professor Richard Shine, ABC Radio National ‘Breakfast’ program, 6 April 2006 (8:25am). The ABC website has audio available for four weeks after broadcast date; it also has a short written summarizing introduction. Return to text.

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