The Beak of the Finch: The Story of Evolution in our Time
(Jonathon Weiner, New York:Alfred A. Knopf, 1994. 332 pp)
Pat Duffy Hutcheon in Brock Review (1995) Vol.4, No.2, p.87-9.
KEY TERMS: Jonathon Weiner -- Rosemary Grant -- Peter Grant -- Galapagos Islands -- natural selection -- sexual selection -- speciation -- species variability -- evolutionary arms race
This is an exceptionally important and timely book for at least two reasons. In the first place, it renders both the fact of evolution and the most powerful theory ever devised for explaining it readily comprehensible to the general public. In contributing to this essential educational task, the author joins the honorable company of writers like Stephen Jay Gould and Richard Dawkins and, like them, demonstrates an admirable capacity for expressing complex ideas simply and clearly. Secondly, Weiner's masterpiece provides a scientifically compelling refutation not only of the claims of Creationists, but also of the criticisms of many dissenting evolutionary theorists concerning the adequacy and continuing fruitfulness of Darwinism as a guiding conceptual paradigm. Both objectives are achieved through the immersion of the reader in an exciting and carefully documented account of the ongoing operation of what Darwin had presciently surmised to be the major force driving evolution: the engine of natural selection. This process is presented not merely as something that happened only once, and in the distant, unwitnessed past, but as it is actually occurring all the time and all around us -- available for all to see.
Communicating so much, and at so many levels of abstraction, is no easy task. Weiner manages this largely by centering his book on the heroic and groundbreaking work of Peter and Rosemary Grant in the Galapagos Islands, and by moving back and forth between their research project (always with a focus on its theoretical significance) and the almost accidental discoveries of Darwin that began in the same area approximately a century before. This approach introduces and sustains in the reader a sensation of mystery unraveling that equals in fascination the best of modern detective thrillers.
Weiner tells how, in the early 1970s, the Grants became interested in the issue of variability in species. This was the very fact which, when observed by Darwin among the finches of the Galapagos Islands, had led to his revolutionary breakthrough. The Grants wondered why variability is itself so variable from species to species. They decided that Darwin's hypervariable finches, in their isolated island environment, might well provide the key to a critical gap in our knowledge of evolution. They began by obtaining measurements on twenty-one varieties of finches found on seven islands. The potential of the project became immediately apparent, as the research team realized that the accuracy of measurement and sophistication of mathematical analysis made possible by modern technology were revealing a degree and rate of variability hitherto unimagined by scientists.
The Grants proceeded to establish a long-term study on one of the Galapagos islands known as Daphne Major. This allowed them to follow events in the lives of the finches over the various seasons and through at least two radical alterations in climate, from an extreme and lengthy drouth to an equally extreme wet season. They were able to witness competition for scarce food as it was actually occurring; and to document the observable changes resulting within the finch populations over the generations. What they saw was a kind of evolutionary arms race which served to emphasize the interactional nature of selection processes, as changes in the shape of the finch's beaks drove the evolution of their food sources, and vice versa. They saw natural selection forcing a species to evolve in one particular way until, when the environmental challenges eased, sexual selection took over and gradually brought about a drastic change in direction.
Weiner suggests that the Grants' work vastly enriches our understanding of the nature of the competition driving both natural selection and sexual selection. As he expresses it, their findings force us to recognize that "Darwinian competition is not only the clash of stag horns, the gore on the jaws of lions, nature red in tooth and claw. Competition can also be a silent race, side by side, for the last food on a desert island where ... the only sound of battle is the occasional crack of a Tribulus seed."
Weiner explores, as well, the extent to which these researchers have shed new light on the problem of origin of species. Their findings demonstrate how both of Darwin's processes of selection intertwine in nature to create those invisible boundaries which result, over time, in the inability of members of one group of organisms to breed with those of another. The Grants found that not only do the finches possess extremely variable beaks, but that they are exceptionally sensitive to these variations. The result is that a slight change in beak shape or size can have devastating effects for the survival of individuals, and for their chances of mating and reproducing. It was also discovered that finch size, and the characteristics of their beaks, are all highly heritable. Taken together, these three factors speed up the selection process considerably, making the finches a particularly fruitful subject for research on the ongoing evolution of species.
Weiner shows us how the roles of natural selection and sexual selection in the origin of species have been clarified and updated by the Grants' work. He also explains how these researchers and their students discovered that -- in times of environmentally induced stress -- the splitting off of a new species can be initiated by a very small thing, such as a minor change in the song of a few of the male birds, which makes them stand out and thus appear more attractive to the most successful females. He also notes the relevance of recent findings of molecular biologists. They have found that the mutation rate is greatly increased by stressful conditions, making the potential for rapid and varied change much greater than usual in these situations. In addition, we are told of the discovery that species divergence (or "fission") and species recombination (or "fusion") are going on all the time. The Grants learned that, in this vital sense, evolution is very far from unidirectional, and that the origin of species is very far from being an extraordinary event, even in real time. Nor, they found, do we need to look for any causes other than those commonplace selection pressures which are continuously initiating and perpetuating lesser types of changes in individual organisms.
The results of a number of other recent research projects corroborating and expanding upon the findings of the Grants and their collaborators on Daphne Major are also presented by the author. For example, he tells us how the evolutionists, Theodosius Dobzhansky and Olga Pavlovsky, discovered the spontaneous origin of a new species of fruit fly. He also describes how Dolph Schluter has documented a similar kind of species divergence among the stickleback in British Columbia lakes. These findings and many others support the conclusion that, although Darwin's essential selection processes operate throughout, under rapidly changing environmental conditions, speciation can occur at a much faster rate than the founder of evolutionary science had ever thought possible.
So, too, is the destruction of species speeded up by extreme disruptions of the environment. This brings us to certain unsettling conclusions forced upon us by Weiner's entrancing tale. In chapters entitled "The Stranger's Power" and "The Resistance Movement" he provides evidence to show how the behavior of humans is affecting the evolution of life on earth in increasingly deleterious ways. He notes recent startling changes in animal and plant populations, in disease-causing organisms, and in insects and weeds: all being wrought by ongoing processes of natural selection which should have been readily foreseeable. If we had understood Darwinian theory, we could have predicted the evolutionary consequences of our thoughtless and inadvertent introduction of new organisms into established ecologies, and of our indiscriminate use of antibiotics and pesticides.
No one could read this book without gaining a renewed appreciation for the genius of Charles Darwin, and for the lasting power of his remarkable theory. Nor could anyone read it and ever again look at the world with the same old eyes. For, in the end, Weiner's greatest contribution may well be his impact on the prevailing world view determining our ways of thinking and valuing. No longer will it be possible for reasonable people to think of evolution as something abstract and irrelevant to their current situation -- of concern only to biologists. We will have to face up to the fact that we are all involved in the process of natural selection; that every living thing is, to some degree, affecting the future viability of other lives. We will be forced to acknowledge the dismaying fact that, if we persist in refusing to accept the implications of Darwinism for human behavior, we are bound to join the ranks of the dinosaurs and other unknowingly suicidal species. Our prevailing combination of blissful ignorance and good intentions will not save us, nor the many threatened species that depend on us. For if this valuable book can teach the modern non-scientific reader anything, it is that, in this vast nature of which we are a part, consequences are all!