Are there snakes in people's heads?

Just for the fun of it, I did a Google search this St. Patrick's Day to find out if there really aren't snakes in Ireland. The legend is, after all, that St. P cast them all out. It appears that it is true. The likely explanation is that after the last Ice Age, when the Isles were off-limits to cold-blooded creatures, Ireland broke away from the continent first. The snakes made it to England before the channel opened, but Ireland was already an island. As I looked through online comments, I found a some interesting ones.

• There are no snakes [in New Zealand] either, but reading these other answers has got me wondering why not. After all, there are plenty of snakes in Australia, and we were once attached to Australia. And can snakes swim?? Also, there are plenty of lizards and other reptiles here, in the native bush and rural areas, so why no snakes? Not that I want snakes...
  
  Helen, Christchurch, New Zealand

• Helen from NZ has a valid point worthy of response by a zoologist or palaeontologist. Scientists who advocate evolution use the "island drifting away from continent" theory as proof that similar colonial animals (e.g. marsupials around Australia) have evolved there through segregation. Marsupials do live elsewhere (e.g. America) and the same evidence would suggest snakes in Madagascar and New Zealand, but there are none. Science can be very subjective or reverse its own logic when it suits, it would seem. P.S. Snakes can swim well.
  
  Steve, Nantwich England

Well, if that isn't a load of loaded words! "Advocate evolution." "'island drifting' theory." "Proof." It was easy to see his conclusion coming: science is subjective and reverses it's logic when it suits. He caps it off with a deft rhetorical flourish: "Snakes can swim well." Ha hah! If that didn't disprove science, invalidate gravity, and make computers everywhere stop working I don't know what will!

For those who don't know my family, my brother is a professor of genetics, my sister is a wildlife biologist, and my father a preacher. But I don't know any scientists who "advocate" evolution. Neither do I know any that are not persuaded by the evidence. Evolution is not a political position, it is a scientific theory. And for those who believe that "theory" means you can decide for yourself if you believe it or not, I invite you all to disbelieve the theory of gravity, and prove it with the help of a tall building.

Steve's biggest mistake, however, is believing that the explanations for no snakes in Ireland are scientific in the first place. They are based in scientific observations, yes. But they do not, in any way, prove that snakes could not live on Ireland. In fact, there is no evidence that any of these observations was the cause of snakes not being in Ireland. After all, as Steve observed, (some) snakes can swim well. Maybe there would have been snakes in Ireland, except that some weather condition in the mid Atlantic caused predatory fish to move into the Irish sea and devour the colonists en route. Could have happened. If there is one question science is lousy at answering, it is "Why didn't" something happen.

I find it amusing that these, shall we call them, "science skeptics" generally base their arguments on an insistence that science must be either true or false. This sort of thinking not only concludes that cigarettes don't cause lung cancer, because 3 pack a day Aunt Trudy lived to 99, but it can equally disprove the strength of steel, because did you see the way it crumpled in that car accident? Aluminum is also heavy. Ever try to pick up an airplane? The skeptics have their own inconsistencies, because they dismiss science and evolution, but when a scientist, using (among other knowledge) the theory of evolution, compounds an antibiotic, they take it. They believe scientists can build computers. But when the scientist explains why the computer works, they call it all subjective and self-contradictory. Luckily for them, scientists don't believe inconsistency invalidates all arguments, or they'd be able to dismiss anything the skeptics said.

The marsupial example is a wonderful case in point. Isolation in Australia allowed marsupial mammals to flourish. Marsupials are at a competitive disadvantage compared to placental mammals with their faster metabolism. But a disadvantage doesn't mean that marsupials can't compete, it means, most of the time, they don't. Out of the tens of thousands of mammal species in the Americas, it is not only possible that one of them might be a marsupial holding on in a particular ecological niche, it's actually likely. One marsupial among twenty thousand placental mammals doesn't disprove the "theory" that marsupials are at a disadvantage. Rather, it demonstrates the case quite nicely.

Evolution, for it's part, isn't just an "explanation" for how things got to be the way they are. It is, rather, a theory--call it a "model," if you will--that can be used to predict outcomes with a high degree of accuracy. You can watch it in action. You can use it to make pharmaceuticals, introduce mutations, establish genetically modified organisms. It is neither "advocated" nor "believed." And if someday some insight displaces the theory with an even more accurate model, that doesn't invalidate science: that is science working.