Friday, November 17, 2006

Is it Evolution or Adaptation?

The article 'Short Legs Win Evolution Battle' is a focal point in determining what evidence supports evolution and what would support a design inference.

An environment that favors faster runners and the longer legs that enable faster running is presented as an example of observed evolution. Brown anolis lizards can live both on the ground and in trees. When predators were introduced into an environment containing the lizards, the predators of them reduced their population but survivors were found to have longer legs. The longer legs enabled the lizards to run away faster from the predators. In a following time period shorter legs, associated with easier tree navigation, were observed to correlate with more time spent by these lizards in trees. The tree dwelling avoided predators. In both time periods advantages conferred by limb length corresponded to adaptive behavior aligned with increased survival chances.

Is this evidence for evolution or adaptation? Are they one and the same or does adaptation occur within phenotypic limits? Could this be evidence for design? Answers should be based on the underlying genomic changes that generate changes in phenotype. If, for example, the alleles for the long and short legs existed within the lizard genome at the time the predators were introduced, then what we could be observing is mere allele variation back and forth. If, on the other hand, the changes resulted from new genomic features, made possible through genetic mutations, the analysis would be affected by this. I suspect the former dynamics account for this observation.

If so then what are the answers to the questions posed? The observations would record evidence for adaptation within limits. This could be evidence for built-in design flexibility. Evidence for evolution would entail data supporting the hypothesis that novel systems, containing multiple proteins, came about through random, selected mutations. That was not the type of evidence provided by this article.

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