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Wednesday, 09 August 2006 00:00

Beak tweaking or evolution

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One of the tenets of the theory of evolution is a phenomenon known as character displacement. Character displacement states, in essence, that when two similar species inhabit the same environment and compete for the same resources, natural selection favors a divergence in characters – be it physical or behavioral.

Usually evolutionists are left searching fossil and scientific records for puzzle pieces that point to character displacement that occurred over long periods of time.

But recently, Princeton researchers Peter and Rosemary Grant reported in the journal Science that one of Darwin’s Galapagos finches, Geospiza fortis, the medium ground finch, has experienced character displacement in just a couple of decades. According to the Grants’ research, the large ground finch, Geospiza magnirostris arrived on the Galapagos island of Daphne Major in 1982. Before the large ground finch arrived on the island, the medium ground finch was top finch, eating seeds of all sizes. Those (G. fortis) with larger beaks fed on larger seeds while those with smaller beaks fed on smaller seeds.

Once a breeding population of G. magnirostris established itself on the island, competition for large seeds revved up. The larger newcomers with their larger beaks were more adept at feeding on big seeds and were soon out-competing the smaller medium ground finches with larger beaks. The medium finches with smallish beaks were content to feed on smaller seeds that did not interest the larger birds, and they continued to thrive.

A drought hit the islands in 2003 and 2004 greatly reducing the number of seeds available. Researchers noted that both species of finches suffered during the drought, but that segment of medium ground finches still vying for larger seeds was particularly hard hit.

Peter Grant described the scenario for the July 14 National Geographic News: “With the near removal of the supply of large seeds, the large-beaked birds [among] the medium ground finches did not have enough food to survive,” Peter Grant said. “They died at a faster rate than the small-beaked members of the population.”

In a single generation G. fortis, on Daphne Island, went from a population exhibiting varying bill sizes to one comprised of all smaller-beaked birds as a result of direct competition for a limited food source.

Intelligent Design proponents were quick to try and discredit the Grants, probably more because of the “Instant Evolution” title of the National Geographic piece than the research published in Science. Much of the ID argument was relegated to knee-jerk ad hominem attacks on the researchers for being evolutionists, like this one from the blog CREATIONEVOLUTIONDESIGN: “ID biologist Jonathan Wells notes that the Grants are prone to ‘exaggerating the evidence’ in that ‘they have tried to make more of their work than the evidence warrants’ and ‘this exaggeration [of the truth] seems to characterize many claims for Darwin’s theory.’”

I don’t believe the Grants were positing that they had witnessed the origin of a species. The abstract to their Science article — “Evolution of Character Displacement in Darwin’s Finches” — states, “These findings support the role of competition in models of community assembly, speciation, and adaptive radiations.”

The paper was a study of the effects of direct competition and natural selection, both integral parts of the theory of evolution on character displacement.

The rapidity (one generation) of the change was of particular note to some biologists. David Pfening, biology professor at the University of North Carolina at Chapel Hill noted in the National Geographic piece that the biggest surprise for him was ‘“the apparent speed with which the character displacement occurs—within a single year!”’ Pfennig added that the study suggests that evolution due to competition between closely related species ‘“paradoxically may often occur so rapidly that we may actually miss the process taking place.”’

Of course if some intelligent designer swept onto the island under the cover of darkness and tweaked beaks, we would miss that too.

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