Friday, 22 April 2016

Evolution Observed in Darwin's Finch

Meduim ground finch, Geospiza fortis
A beak size locus in Darwin’s finches facilitated character displacement during a drought | Science

Every now and then we get an exquisitely simple and irrefutable example of evolution being witnessed and reported with supporting data. Despite this, however, creationists continue to deny that evolution occurs and continue to chant their dogmatic insistence that it has never been observed.

Firstly, the scientific evidence:

Abstract
Ecological character displacement is a process of morphological divergence that reduces competition for limited resources. We used genomic analysis to investigate the genetic basis of a documented character displacement event in Darwin’s finches on Daphne Major in the Galápagos Islands: The medium ground finch diverged from its competitor, the large ground finch, during a severe drought. We discovered a genomic region containing the HMGA2 gene that varies systematically among Darwin’s finch species with different beak sizes. Two haplotypes that diverged early in the radiation were involved in the character displacement event: Genotypes associated with large beak size were at a strong selective disadvantage in medium ground finches (selection coefficient s = 0.59). Thus, a major locus has apparently facilitated a rapid ecological diversification in the adaptive radiation of Darwin’s finches.


Copyright © 2016, American Association for the Advancement of Science.
Reprinted with kind permission under licence 3854221099034

The same team had earlier shown that another locus (ALX1) was involved in controlling beak size. The field-work was carried out by Peter and Rosemary Grant during a forty-year period.

We previously documented that the average beak size of the medium ground finch population became smaller during this drought due to a high mortality among individuals with large beaks because they could not compete well with the large ground finch,' say Peter and Rosemary Grant, who carried out field work on the Galápagos during a 40 year period. Now we have demonstrated that the HMGA2 locus played a critical role in this evolutionary shift and that natural selection acting on this gene during the drought is one of the highest yet recorded in nature.

Peter and Rosemary Grant, co-authors.
Quoted in ScienceDaily
Quite plainly, and unambiguously, this paper shows that, because of the effects of a severe drought and due to competition with the large ground finch (Geospiza magnirostris), there was a change in the allele frequency of a gene that controls beak size in the medium ground finches (G. fortis) on Daphne Major - one of the Galápagos Islands - and so the mean beak size in the population was reduced and G. fortis further diverged from the closely-related G. magnirostris.

In the prevailing environmental conditions there was an advantage in having a smaller beak, so selection pressure ensured more descendants had the allele which produces smaller beaks and fewer had the allele producing a larger one. This, of course, is exactly how biological science defines evolution - change in allele frequency over time. A classic case of evolution by natural selection, clearly and unambiguously observed and recorded.

Creationists of course, must find some way to cope with this irrefutable evidence because it isn't what their dogma requires. The normal way will be for them to try to insist that actually, the scientific definition of evolution is something entirely different. The ploy will normally be to demand that evolution is all about one species changing into another and that the scientific theory of evolution claims that this happens in a single event involving lots of mutations all occurring together.

Maybe a creationist could explain to me why the example given is not an example of recorded and observed change in allele frequency over time in a population, due to natural selection. Alternatively, maybe a creationist would explain why we need to pretend the theory of evolution is something else so they can continue to tell themselves that it doesn't happen.

Don't you just love it when creationists are forced to choose between admitting they are wrong and showing how they need to misrepresent science to retain their idiotic superstition?


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