Wednesday, June 3, 2009

Chicken vs. Egg: finally settled

You've heard the question, "What came first, the chicken or the egg?"

I was listening to a podcast that I love to hate, Intelligent Design the Future, and was reminded of that age-old conundrum. In case you're not familiar, Intelligent Design (ID) is a world view that posits that life could NOT have evolved, but instead must have been designed by an intelligent agent (translation: ID is good ol' creationism gussied up with a new suit and a new name). ID proponents spend most of their time fighting off their inevitable hostile takeover by the amazing theory of evolution. Though they call their theory scientific, they offer little science; it's mostly about trying to punch tiny holes in evolution so that they can continue believing in their religion.

One particular argument they spout is that evolution has never been observed. Evolution, by its very nature, takes a long time. The reason it even had to be discovered in the first place (as opposed to being dismissively obvious) is because it takes so much longer than a human lifetime.

Oh, I'm sorry. ID proponents don't categorically denounce evolution; they DO concede that micro-evolution occurs. That is, they agree that selective breeding can lead to changes in gene frequencies in a population, and cause certain traits to become exaggerated. Dog breeding is a canonical example.

However, they draw the line at macro-evolution, the idea that small changes in a population's genome can accumulate over time and create a new species. The most compelling reason for this denial is a lack of imagination. They have difficulty imagining how a bird could evolve from a dinosaur, so instead they focus on silly distractions like, "Has anyone ever seen a dog give birth to a duck? Of course not, so evolution is a fraud!" The podcast was talking about how SARS, the bird flu, and swine flu all failed to cause a pandemic. Their argument is that since the viruses didn't evolve even that little bit further to cause a pandemic, then nothing ever evolved. To point out how wrong this is, let me apply the same logic to a different scenario: I didn't have a heart-attack today, therefor I will never have a heart-attack.

It seems inevitable that small alterations in the genome of species "A" will, over time, accumulate until it no longer seems appropriate to call it species "A" anymore. That's called speciation. In fact, it's actually more difficult to imagine speciation NOT occurring.

OK, back to the chicken and the egg. I expect that the ancient ancestors to chickens also laid eggs. So, every chicken must come from an egg. What's not so clear is that every egg has to yield a chicken. For a sexual-reproducing species like chickens, every offspring is different from its parents. At some point in history, a species of birds accumulated enough genetic changes from its ancestor species to warrant a new name. The first organism of that new species must have first been an egg. Hence, the egg came before the chicken.

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