Sunday, February 11, 2007

Evolution of New Species Does Occur and Here's How to Picture it and Support it with Evidence

Since tomorrow is Charles Darwin's 198th birthday, I decided to take some time to pass on an excellent visualization of evolutionary speciation that my high school biology teacher utilized.

Before I begin, let me define speciation. Also called macroevolution, it is the evolutionary process by which new biological species arise. For creationists, this is one of their largest points of contention. They argue that no species of animal has ever been observed giving birth to a different species. While certainly true, this is not how the theory of evolution says new species will arise. If an animal's offspring were a different species, that would probably serve better as proof for Creationism more than evolution. As a rule, an animal will always be the same species as their parents. Then how does evolution say new species will arise? Well, come along and I'll relate the excellent example my biology teacher told me.

Let's say you have a species of frog that lives in Florida. It's particularly successful and multiplies quickly. This obviously causes competition for food and forces the frogs to spread out so they can find more food. This spread serves as a form of migration and eventually these frogs and their descendents spread out so far that they span from Florida to New York (obviously, this is a bit large for frogs and they would more likely spread east and west since the climate changes aren't as extreme, but follow along for the sake of argument). However, the environment at each latitude is a bit different and favors certain mutations within the frog population. They might have to eat different foods, the climate might change their mating patterns, their coloration might change to blend in with the different vegetation, et cetera. Sure, these are all examples of microevolution and do not make it a new species, but with enough changes you start to get something different with the variations becoming greater the farther away you get from the original habitat.

Now, the frogs in Virginia will be a little different than the original population, but the Florida frogs and the Virginia frogs will still be able to breed with each other since they are not as different and might still intermingle. On the other hand, the New York frogs will have taken much longer to get where they are and have a much different climate than Florida, causing them to change even more than the Virginia frogs, but they can probably still interbreed with the Virginia frogs since the separation in time and space is once again not terribly large. However, the New York frogs cannot interbreed with the Florida frogs since they have had too many changes to successfully interbreed and produce viable offspring, thereby making the New York frogs a new species. It wasn't quick or sudden, but it eventually led to speciation. Put simply, the frogs can breed with their neighboring populations, but not the next population over.

Of course, this is just a theoretical illustration and would be useless if it didn't have any evidence to support it. So, is there any evidence? Yes. Just look at mules. Mules are created by breeding a male donkey with a female horse. However, donkeys and horses are still separate species because mules not viable, i.e., they are sterile (except for extremely rare cases). This shows that horses and mules were once part of the same species. However, there were population migrations and the group that lived in the Asian steppes eventually became horses that adapted to living in open grassland while the group that settled in northern Africa became the wild ancestors of donkeys and adapted to subsist on more meager resources. However, they are still similar enough to interbreed and produce young, albeit sterile. It's an excellent example of recent speciation. The ability to breed a lion and a tiger to produce a sterile liger is a similar example.

Now that we've seen evidence for recent speciation, can we find evidence for speciation in progress? Yes. All you need to do it look at ourselves and the existence of different races. Early humans spread out from Sub-Saharan Africa to span the reaches of the globe. As they moved to different climates, they began to adapt. Sunny Africa favored dark-skinned humans, Asia favored a similar adaptation, although to a lesser degree, and cloudy Northern Europe favored humans with paler skin. Nevertheless, human populations weren't isolated from each other long enough to develop different species, and the devlopment of transportation technology allowed us to intermingle once again, finally preventing it. However, if the different races had remained isolated from one another, then we certainly would have seen the speciation of different humans with homo sapiens as the common ancestor. Of course, you could compare this to the Bible-friendly explanation from Answers in Genesis. I'll let you be the judge.

In conclusion, speciation or macroevolution is really not too hard to understand and accept when you just look at the world around us. The evidence for it is easy to find.

P.S.: In my discussion, I used the out of Africa hypothesis to explain the existence of different races. You can see the other scientific hypotheses here.

Update: Here's a good article about a new find that supports the out of Africa hypothesis.

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