Download Science Tear Sheet #6. Darwin‟s Finches

Science Tear Sheet #6. Darwin‟s Finches
The Claim. In developing his theory, Darwin relied heavily on observations of several finch species
from the Galapagos Islands. These thirteen species demonstrate different behavioral and physical
characteristics, although they likely originated from one original finch species. Especially noteworthy is
the variation in average beak size among the different species, which corresponds to differing dietary
habits and survival rates during droughts and periods of high rainfall. Over long periods of time, natural
selection has worked through such conditions to favor finches with differing characteristics, resulting in
multiple species. Thus:
Variation + Natural Selection + Time = Evolution
The Evidence Presented. To support the claim that the Galapagos finches demonstrate evolution, some
textbooks cite the modern Pulitzer Prize-winning book, The Beak of the Finch, which details the work of
scientists Rosemary and Peter Grant of Princeton University. The Grants have documented that over
time, the average finch beak size has changed due to selective pressures. During extended periods of
drought, finches with large beaks fare better than those with small beaks, as they can more easily crack
the dry, hard-shelled seeds on which they feed. Small-beaked finches, on the other hand, seem to flourish
during periods of wet weather, when soft-shelled seeds are plentiful. Thus, when local weather patterns
change drastically, the frequency of large- and small-beaked finches in the overall finch population is
altered. Extrapolating these trends, the Grants speculate that recurring droughts could lead to the
emergence of new finch species.
The Beak of the Finch explains the process of natural selection observed among Galapagos
finches as “the best and most detailed demonstration to date of the power of Darwin‟s process.”i Oxford
University‟s William Hamilton concurs, characterizing the Grant‟s fieldwork as providing “the most
detailed unified support to the Neo-Darwinian view of evolution that the theory has yet received.”ii
The Full Story. The central issue surrounding the finches is whether they constitute examples of
evolution (meaning macroevolution). Based upon the discussion of limited variation in within a species
in Tear Sheet ##, the answer is decidedly negative. Although some finch species are ground-dwellers,
and others, tree-dwellers; although some eat seeds, and others, insects; although some have small bodies
and small beaks, and others, large bodies and large beaks, all are clearly finches. These creatures become
evidence for evolution only when one extrapolates observed examples of limited variation and infers that
such changes will continue until a new species type (a non-finch) is established. But there is no support
for such an inference. The accepted and observed processes of limited variation, recombination, loss of
genetic information, and selective pressures can account for all variation observed among the finches.
These observed processes differ greatly from the addition of genetic information needed to support the
notion of (macro) evolution. And in science, an adequate explanation requiring no unobserved processes
is preferred over alternatives requiring speculation and unobserved processes.
The Grants observed a drought-related variation of 1.02 millimeters (an increase from 10.68 mm
to 11.7 mm) in beak length in the finch species Geospiza fortis. Although hailed as “the most intense
episode of natural selection ever documented in nature,”iii this variation amounts to about three times the
width of the period at the end of this sentence. Anyone seeking supporting evidence for Darwinism
would rightly be troubled if this minor variation in finch beak length does indeed constitute the best
available evidence for natural selection.
There are many more reasons to regard the finch beak evidence as weak. Interbreeding among
most finch species produces fertile offspring; therefore, most are of the same species (a widely accepted
definition of „species‟ being that they produce fertile offspring). Even Peter Grant concedes: “At the
extreme, six species would be recognized in place of the current 14, and additional study might
necessitate yet further reduction.”iv This means that despite historical references to the finches as separate
species, it is more accurate to refer to the Galapagos Islands finches as consisting of one to six species.
Continued designation of the finches as separate species is justified only if species are to be defined based
on differing size, diet, and place of habitat, rather than on the ability to produce fertile offspring. This
approach is clearly not appropriate, as even modern man would have to be classified as consisting of
multiple species using these alternative criteria.
Second, textbooks fail to point out that according to the Grants‟ research, following severe
droughts (when the average finch beak length increases), the average finch beak length tends to revert
back to its original size. In other words, the trend towards a new finch species is lost once heavy rainfall
occurs. Following heavy El Niño rainfalls in the early 1980s, natural selection prompted such a reversal
in favor of smaller finch beaks. As a result, the fortis finches born after heavy rainfall have beaks
“measurably narrower than the beaks of the generation before them—down from 8.86 millimeters at the
time of the flood to 8.74 millimeters now.”v Thus, the real story of the finch beaks is one of stability over
time, not change. An article in the April 26, 2002 issue of Science points to this conclusion, as it contains
a graph showing the body size, beak size, and beak shape for two finch species (G. fortis and G.
scandens), indicating oscillations around long-term values.vi Again, such a reversion to the mean is
further evidence against evolution, as it suggests stability of species over time. And yet, because
evolutionists equate Darwinism with any kind of change, they conclude that the oscillating changes just
described conclusively prove that “the fortis have evolved.”vii This is an incredibly misleading statement.
So how do the Grants extrapolate their data to argue that a new species of finch could arise in a
two-hundred-year period if droughts occur every decade?viii By assuming that the changes are cumulative
over time and that there is no reversion back to the original finch beak size. However, this is a very poor
assumption, for it contradicts the Grants‟ own research.
Finally, the research of Peter and Rosemary Grant has shown that rather than branching into an
increasing number of species, the Galapagos finches are interbreeding, and the resulting hybrids are
flourishing. After the heavy rains of the early 1980s, the Grants found that a cross between the G. fortis
and either the G. fuliginosa or G. scandens finch “does the genes of fortis a favor.”ix Likewise, in a 1992
Science article, they concluded that “hybrids exhibit higher fitness than the parental species over several
years.”x Furthermore, some ten years later, the Grants indicated in Science that they had observed two
finch species interbreeding with G. fortis, and “In both cases there is generally little or no fitness loss.” xi
If these trends continue, the number of species may be reduced, not increased, as natural selection favors
the hybrid finches to the detriment of the pre-existing varieties. The Grants project that if crossbreeding
between G. fortis and G. fuliginosa continues, all morphological differences could disappear in less than a
century or two.xii Aside from demonstrating that the two finch populations are varieties, not species, these
results confirm that it is inappropriate to simply define evolution as “change.” Darwinism predicts
increased speciation over great periods, not the quick reduction of varieties within a species.
In sum, the Galapagos finches fail to demonstrate that natural selection provides for the
emergence of new species types (a non-finch). Even if the finches powerfully demonstrated natural
selection, this alone would still not equal macroevolution. Natural selection can act to favor certain
variants within a species, but it is not a mechanism producing the variations required by Darwinism. It is
therefore misleading to present examples of limited variation as proof of evolution.
For Discussion:
1) Discuss why Darwin‟s finches demonstrate limited variation within a species but not Darwinism.
2) If the scientific literature acknowledges multiple problems with the peppered moth experiments
and concedes that natural selection does not equal Darwinian evolution, then why is this not
explained in high school textbooks? What role does one‟s philosophy/worldview have on the
issue?
Note: the discussion above is copyrighted material by Restoring Truth Ministries, LLC, and is a
condensed version of the material in Repairing the Breach: Explaining the Systematic Deception Behind
the War of Worldviews and How Christendom Can Turn the Tide by John M. Wynne and Stephen A.
Wynne. The book can be ordered from www.restoringtruthministries.org. This Tear Sheet and additional
Tear Sheets can be downloaded from the website, copied, and distributed without payment to Restoring
Truth Ministries, LLC, provided that copies are distributed without charge to the recipients.
Alternatively, bound copies of all Truth Tear Sheets from Restoring Truth Ministries, LLC covering
issues in science, sex education, and American Government can be ordered from
www.restoringtruthministries.org for a low cost fee covering printing, binding, and handling costs.
Students and teachers are encouraged to make this material part of the discussion of Darwinian science.
Where schools are not willing to allow criticisms of Darwinism, it is all the more important for the Tear
Sheets to be distributed outside of class and for students to ask questions about the deceptive Darwinian
claims presented in textbooks.
i
Jonathan Weiner, The Beak of the Finch (New York: Vintage Books, 1994) p. 9.
Ibid., p. 19.
iii
Ibid., p. 78.
iv
Peter R. Grant, “Hybridization of Darwin‟s finches on Isla Daphne Major, Galápagos,” Philosophical Transactions of the Royal
Society of London, Series B, vol. 340 (1993), p. 138.
v
Weiner, p. 192.
vi
Peter R. Grant and B. Rosemary Grant, “Unpredictable Evolution in a 30-Year Study of Darwin‟s Finches,” Science, vol. 296,
26 April 2002, p. 708.
vii
Weiner, p. 192.
viii
Grant, “Natural Selection and Darwin‟s Finches,” pp. 82-87.
ix
Weiner, p. 193.
x
Peter R. Grant and B. Rosemary Grant, “Hybridization of Bird Species,” Science, vol. 256, 10 April 1992, p. 193.
xi
Grant and Grant, “Unpredictable Evolution…,” p. 708.
xii
Weiner, p. 197.
ii