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Darwin’s Finches Don’t Point to Evolution

Galapagos Island ground finch: Photo 14526711 © Matthewgsimpson |

[Originally published as Genetics of Darwin’s Finches]

The finches Charles Darwin encountered on the Galapagos Islands served as one of the most enduring examples of evolution throughout the twentieth century. As Darwin explains in The Origin of Species, “one [finch] species had been taken and modified [changed] for different ends” — the essence of natural selection. However, the technology to scientifically validate these changes in the genetics of Darwin’s finches was inconceivable in the nineteenth century.

Since then, advances in molecular technologies allow for the testing of evolutionary genetic changes, including the genetics of Darwin’s finches. In the most comprehensive investigation to date, a team of scientists led by Sangeet Lamichhaney of Uppsala University in Sweden published their paper entitled “Evolution of Darwin’s finches and their beaks revealed by genome sequencing” in the prestigious journal of Nature.

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Lamichhaney Study Design

The study focused on the shape of the bird’s beak and its associated gene, the ALX1 gene. Blood samples were gathered from 120 captured finches and grouped by location: the Galápagos and Cocos Islands and two closely related tanagers from Barbados.

Once the samples were collected, the groups were released back to their original location. Genetic analysis was performed in the laboratory using the Genome Analysis Toolkit.

Team Findings

Lamichhaney’s team of scientists reported finding “important discrepancies with the phenotype-based taxonomy.” Specifically, the shape and size of the beak, also known as the “phenotype,” did not correspond to the ALX1 gene, known as the genotype, as predicted by Darwin’s theory.

Rather than finding genetic differences between presumed distinct species, the evidence indicates gene sharing within the same species. As Lamichhaney explains—

Extensive sharing of genetic variation among populations was evident, particularly among ground and tree finches, with almost no fixed differences between species in each group.

A pattern of “slight, successive” evolutionary changes, as predicted by Darwin, was not observed. The evidence points to interbreeding rather than speciation. Gene flow between the groups is compatible with interbreeding. As the investigators reported—

We find extensive evidence for interspecific gene flow [interbreeding] throughout the radiation [groups].

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Noting the “considerable amount of genetic diversity within each population,” the investigators issue the following warning—

The exact branching order of the… ground and tree finches should be interpreted with caution.

Geoffry Mohan writing for the Los Angeles Times, reported that the “species that were genetically similar on one island were not as closely related on others… [that] can be interpreted as evidence of interbreeding.”

Interbreeding can only produce fertile offspring within a single species. Based on the genetics of Darwin’s finches, then, the evidence points to a variable single species population on the Galápagos Islands.

Corroborates Findings

Lamichhaney corroborates the findings of previous investigations. Stephen O’Brien, Genome 10K Project co-founder, had anticipated in 2012 that “the genome sequence empowerment of Darwin’s finches will initiate the solving of evolutionary riddles that have puzzled biologists for a century.”

Even though the Genome 10K Project had announced that “scientists have sequenced the genome of one of the iconic Galapagos finches as described by Darwin,” the Genome 10K project has still not published any evidence to solve the problem.

Akie Sato of the Max-Planck-Institut für Biologie, Germany, a decade earlier, in the paper entitled “Phylogeny of Darwin’s finches as revealed by mtDNA sequences” failed to separate the finch populations into distinct sequential species, either—

The traditional classification of ground finches into six species and tree finches into five species is not reflected in the molecular data.

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Peter and Rosemary Grant, the husband and wife team who had dedicated their professional careers to the study of Darwin’s finches, confirmed Sato’s observation. In their paper “Comparative landscape genetics and the adaptive radiation of Darwin’s finches” published in the September 2005 issue of the Molecular Ecology journal, they said the scientific evidence points to a “decoupling of morphological and molecular evolution.” The genetics of Darwin’s finches point to interbreeding, not evolution.

Richard William Nelson profile 2013

Written by Richard William Nelson

Richard William Nelson earned a Doctor of Pharmacy degree from the University of Southern California following graduation from the University of California, Irvine, with a Bachelor of Science degree in biochemistry. For more than a decade Dr. Nelson has been writing and speaking on the scientific merits of biological evolution. Dr. Nelson has spoken nationally and internationally to audiences in churches, schools, universities, and community organizations. As the author of the book entitled Darwin, Then and Now, The Most Amazing Story in the History of Science using more than 1,000 documented references, Dr. Nelson advocates using the scientific method to assess the merits of the theory of evolution.

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