August 24, 2005 | David F. Coppedge

Darwin’s Finches Evolve – Back and Forth

What’s new on the Galápagos?  For those needing an update on Darwin’s famous finches, the researchers who have spent the most time studying them – Peter and Mary Grant (Princeton) – wrote a Quick Guide in Current Biology1 in question-and-answer format.  We’ll skip the introductory material about how the birds got named after Darwin, and what makes them special in the history of evolutionary thought, to see if the Grants have any evidence that they have, indeed, evolved.  The key question is: “Are Darwin’s finches still evolving?”

An often asked question may be phrased as follows: what can be said about evolution if it all happened in the past, for surely understanding where our biological diversity came from is then a mixture of scientific inference and inspired guesswork, almost impossible to verifyImperceptibly slow evolution encourages such skepticism.  In the Origin of Species, Darwin wrote “We see nothing of these slow changes in progress until the hand of time has marked the lapse of ages”.
    In fact, numerous studies have demonstrated evolution in action, and the study of finches on the island of Daphne has contributed significantly.  When the environment changes, for example when a severe and prolonged drought occurs, finches die in large numbers, not randomly but size-selectively.  Large finches with large beaks have an advantage over small birds, and survive better, because they are able to crack the large seeds that are relatively common after almost all the small seeds have been consumed.  When they breed the next year they produce offspring with large beaks because beak size is heritable.
    This change from one generation to the next is evolution.  Some time later, the environment changes again, food supply changes, the advantage shifts toward finches with small beaks and correspondingly the direction of evolution changes.  The back and forth process may have a net trajectory toward large or small size, and this is where inference enters the interpretation, because persistent directional changes in structures such as bird beaks are not likely to occur so rapidly that they can be documented in a few years. (Emphasis added in all quotes.)

Moreover, when asked about finch genomics, they claimed the genes of the finches are evolving, though the evidence is only preliminary:

The molecular analysis of finch beaks has only just begun.  In addition to this functional genetic study, molecular markers in the nuclear and mitochondrial genome have been used to estimate the phylogeny of the finches.  With some exceptions they support the traditional grouping of the species on the basis of their plumage and beak characteristics.  Molecular markers have also been used to track the exchange of genes between species that interbreed, albeit rarely, and the finding is dramatic.  They show a pair of species on Daphne in a state of flux, at present converging genetically and morphologically, having diverged strongly in the past.  This nicely captures the evolutionary dynamism that Darwin’s finches display to an unusual degree.

Yet if they diverge then converge back to where they were before, is that really evolution?  The Quick Guide moves on, leaving that question unasked and unanswered.


1Peter R. Grant and B. Rosemary Grant, “Quick Guide: Darwin’s Finches,” Current Biology, Volume 15, Issue 16, 23 August 2005, Pages R614-R615.

There you have it: the world’s leading authorities on the beaks that made Charlie famous, and they don’t add a thing to what young-earth creationists already believe.  The Grants merely repeated what is already admitted by intelligent-design researchers in the films Unlocking the Mystery of Life and Icons of Evolution; any observed changes are mere oscillations about a mean.  These poor devoted people have measured beaks for over 30 years and have not found any persistent directional changes – nor could they be expected to in one human lifetime.  They even admit that today the birds remain interfertile and so have not really undergone speciation after however long they have lived on these islands.  Yet they expect us to think that it is a scientifically sound inference to extrapolate their data, which, in evolutionary terms, constitute noise, into long-term directional trends.
    Inference, interpretation based on presuppositions – that’s what Ken Ham and the most ardent creationists accuse the Darwinists of engaging in without scientific rigor.  We all have the same data, but the interpretation depends on your world view and how much you adore Charlie.
    David Berlinski chuckles at the Darwinistic boasting over this most famous of examples of evolution.  It “doesn’t even pass the threshold of anecdote,” he said in the film Icons of Evolution.  OK, finch beaks adapt to drought conditions, and adapt back when the rains return (the changes are submillimeter differences, by the way).  Fine.  But, Berlinski continues, to be convinced that all the complexity of life could be explained by Darwin’s hypothesis of natural selection, “we’re going to need a whole lot more by way of evidence…. a whole lot more if this is to be serious science.”

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Categories: Birds

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