Wednesday, July 21, 2010

Species I

Once of the common argumentative themes from anti-evolutionists, is what constitutes a species. While it seems like a simple concept, in reality is more a very blurry line than a hard fast definition. Generally accepted a species is a population group that is easily capable of breeding within the group.

That sounds pretty cut and dried, but the reality is there is no absolution definition. It's more a rule-of-thumb. The main reason is that the idea of a species, or any of the other taxonomic ranks (genus, family . . .) is a man-made concept used for classification. Which means that there is no absolute hard-fast rule. This sounds like the waters are muddied, but the reality is that Nature doesn't have this concept built-in, so it doesn't make any mistakes. So the issue is not definitional, but our ability to classify organisms.

Here is an example I have used several times, the London Underground Mosquito. It evolved from an above ground species Culex pipiens, and is called Culex pipiens molestus to highlight that relationship. The namers used the term molestus because of its extremely aggressive behavior. Now, is it a different species? According to our classification system it certainly is. However can it breed with Culex pipiens? Genetically yes; however the difference in behavior, temperament and location, the two groups do not interbreed. So the classification makes sense.

Another example, Polar and Brown Bear. They are also listed as two different species, and yet like the mosquitoes discussed above. They are capable of interbreeding, and in fact a number of polar-brown hybrids exist and, unlike mules, they are not sterile. The dividing line is environmental. Neither bear could survive long in it's others environment so breeding between them is a rare event, but not an impossibility.

There are many other examples where the line between species is a bit blurred, but this is not a negative, as stated frequently by anti-evolutionists. I find this sort of funny because the defense frequently used is based on the biblical use of the word 'kind', which is never defined as to what it is in any sense -- but seems to be defined based on the argument-de'jure depending on whether the anti-evolutionist is arguing against species, genus, family, order . . ..

Remember it's our ability to classify rather than some hard and absolute rule of nature. One day Chihuahuas and Great Danes might be seen as separate species because of the challenge in breeding, but they are currently classified as both being breeds of the species Dog. You should also remember as well that the label of species is usually applied after a great deal of time, and after careful study. There is no one standing there with a label-maker as soon as a new species is born. But that seems to be the only standard an anti-evolutionist wishes to accept. It's nothing more than a demand for some level of absolute in a scientific explanation and a refusal to accept or understand the reality of scientific study. Species exist, but they are classifications and subject to change as we learn more and more about a specific species. No absolutes exist in nature, so no absolutes are going to exist in scientific explanations. We tend to leave absolutes to theists.

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