Never Say Die: Researchers Spend 37 Years Looking for Evolution in Darwins Finches
The Grants are still at it. Peter and Rosemary Grant have been studying Darwin’s finches since the 1970s, looking for evidence to support Darwin’s theory of natural selection. Their latest paper in PNAS produced results that were tentative at best.1
Up front, they had to admit that you can’t see the birds evolving. Evolution is measured in terms of an elusive property called fitness, but the Grants, for all their experience and work, fell into the trap of defining fitness in terms of reproduction: “The fitness of an individual refers to its ability to survive and reproduce, generally measured as the number of offspring that the individual contributes to the next generation.” The problem with this definition is that fitness can represent opposite things – speed or sloth, large size or miniaturization – as long as more offspring are produced. It can even mean production of large numbers of offspring (as in insects) or very few (as in giant pandas), and still qualify as “fitness.” Whatever survives is fit; whatever is fit survives. Defined this way, fitness is a tautology (see “Fitness for Dummies,” 10/29/2002). They added, “The translation of an individual’s potential fitness into realized fitness is governed by the environment,” but they never again explained what differentiates those two terms. Either an individual survives and reproduces or does not; if it only has the potential to do that, how can anyone measure its fitness until it dies and its offspring are counted?
After that unsteady footing, they described how fitness might be determined by scientists. “Although the survival component of fitness is occasionally and strongly influenced by morphology, there is no single morphological determinant of fitness over the long-term because selection oscillates in direction according to the particular nature of the food supply at the beginning of droughts.” Don’t look for muscle-bound finches, in other words. Darwin’s finches have a nasty habit of getting scrawny with droughts and fat in times of plenty (see 08/24/2005). These outward appearances oscillate with the seasons and food supply. A scientist will have to look elsewhere to measure fitness, whatever it is.
In the paper, the Grants tried to measure “lifetime fitness” or “recruitment,” which basically measures relative offspring count at the end of an individual’s life: “Lifetime fitness (recruitment) may be determined solely by producing many offspring, modified by stochastic effects on their subsequent survival up to the point of breeding, or by an additional contribution made by the high quality of the offspring owing to nonrandom mate choice.” The bottom line is how many chicks survive and grow up to pass on the parents’ genes to the next generation. It’s no score, obviously, to produce dozens of chicks that never survive to adulthood or remain celibate – otherwise that could represent an oscillation around the mean, too, over generations.
Their main finding seems little more than common sense: “Regression analysis showed that the lifetime production of fledglings was predicted by lifetime number of clutches and that recruitment was predicted by lifetime number of fledglings and longevity.” That only seems to state the obvious, if not restating the premise: the more sex, the more kids. A breeding pair will score higher the more clutches it has, and the more fledglings they produce over their lifetimes. But even then, can they apply generally what they found on the unique Galapagos environment? “Darwin’s finches deviate from the standard tropical pattern of a slow pace of life by combining tropical (long lifespan) and temperate (large clutch size) characteristics.” Does that mean that what happens in Galapagos stays in Galapagos? If that is so, what are they learning about Darwinian evolution by looking at a special case?
The Grants were able to discount mate choice as a factor in fitness, whatever that is, and “The offspring sired by extrapair mates were no more fit in terms of recruitment than were half-sibs sired by social mates.” Maybe, then, this paper is more noteworthy for what it didn’t find than what it found. Somehow, the Grants kept their positive thinking through it all: “These findings provide insight into the evolution of life history strategies of tropical birds.” Even though Darwin’s finches are atypical, “Our study of fitness shows why this is so in terms of selective pressures (fledgling production and adult longevity) and ecological opportunities (pulsed food supply and relatively low predation).” But selective pressures and ecological opportunities cannot generate the genetic information required to make a bird evolve into something better. The birds were already finches when they moved to the islands, and have not changed all that much in factors that really count (organs, senses, flight, brain, etc). They must have been pretty “fit” (whatever that means) when they first got to the islands.
The chart in the paper shows four cohorts of birds monitored between 1978 and 1987. Now it is 2011. When all was said and done, the Grants admitted that much more research is needed to untangle the factors that might influence the observations:
Thus, there are two components of biological success, in addition to chance, that have a bearing on the combination of life history traits. The first component is an ability to find food (seeds) in dry years when food is scarce and there is no breeding. The second is an ability to find food (insects and spiders) and avoid interference at the nest from intruders during breeding. Identifying the components, which are two different suites of behavioral and physiological traits, shows where further research is needed to gain a more detailed understanding of how fitness is maximized. Such research may yield insight into the question of how lifespan/reproduction trade-offs evolve differently in different tropical habitats that vary in seasonality, elevation, structure, and climate and also between tropical and temperate zones due to differences in ecology and seasonality, as well as other correlates of latitude.
So for 37 years of studying these birds,2 the Grants cannot say that any factor provides prediction of upward and onward gains in fitness, whatever that is. For all they know, each one of these factors has oscillated for thousands of years, or else all the birds would have arrived at fitness nirvana by now.
The end of 2010 marked the 10th anniversary of Jonathan Wells’s book Icons of Evolution, which critically examined the top 10 alleged proofs of Darwinian evolution (peppered moths, the horse series, four-winged fruit flies, Haeckel’s embryos, and others – including Darwin’s finches). Evolution News & Views has been celebrating the book’s anniversary with interviews. It began Nov 30 with an overview video and review by David Klinghoffer. Paul Nelson reviewed the Miller Experiment. Jonathan Wells reflected on his research about Archaeopteryx, Darwin’s Tree of Life, and on homology in vertebrate limbs. In addition, Michael Behe and Casey Luskin each commented on the influence of the book, and today, John West paid a general tribute.
If a segment on Darwin’s finches is forthcoming, the newest paper by the Grants will provide more fodder for Jonathan Wells’ gentle reproof in Chapter 8 of his book, where he praised the Grants’s “excellent field work” (p. 173) but criticized the exaggeration of the actual evidence as support for Darwin’s theory: “evidence for oscillating natural selection in finch beaks is claimed as evidence for the origin of finches in the first place,” he said. “Apparently, some Darwinists are prone to make inflated claims for rather meager evidence” (p. 174). Wells noted that the National Academy of Science referred to this work by the Grants as a “particularly compelling example” of the origin of species, pointing out that, like a stock promoter, they misled the public by touting the increases during good years but not the decreases during years of drought. Quoting Phillip Johnson, he ended, “When our leading scientists have to resort to the sort of distortion that would land a stock promoter in jail, you know they are in trouble.”
1. Peter and Rosemary Grant, “Causes of lifetime fitness of Darwin�s finches in a fluctuating environment,” Proceedings of the National Academy of Sciences, published online before print January 3, 2011, doi: 10.1073/pnas.1018080108 PNAS January 3, 2011.
2. For previous entries about the research of Peter and Rosemary Grant on Darwin’s finches, see 04/26/2002, 09/03/2004, 10/24/2004, 08/24/2005, 07/24/2006, 03/28/2007, 03/04/2008, and 11/13/2008.
Bless their hearts, we hope Peter and Rosemary can find something to console their souls after wasting their lifetimes on a fruitless quest. Take heart. Remember that no experiment is ever a complete failure; it can always serve as a bad example.