In The Beak of The Finch, Jonathan Weiner gracefully intertwines the theory of evolution, scientific discovery, and history. Weiner shows us, through Peter and Rosemary Grant’s work in the Galapagos studying Darwin’s finches, and by human’s environmental wrongdoings, evolution is real and is happening now. By taking a complex, multi-faceted subject and breaking it down through examples and case studies, the author speaks to both the experienced Darwinist and the amateur scientist.

     Weiner’s scientific prose stays on beat throughout the three sections of The Beak of The Finch. Part One: Evolution In the Flesh follows the Grant’s research on the variation and evolution of Darwin’s finches. Through their work, they have seen the fluctuation in beak sizes in response to environmental pressures. Part Two: New Beings On This Earth documents the divergence and convergence of Darwin’s finches. Section Three: G.O.D. (Generation of Diversity) is titled appropriately, for it outlines how humans have contributed to the evolution of species through our manipulation of the environment. Following the summarization of these three sections, the strengths and weakness of the book will be examined. My overall impressions about the book will conclude the review.

     Part One: Evolution in the Flesh opens with the historical background on the theory of evolution by natural selection. As a creationist, Darwin thought species remained unchanging over time and didn’t believe animals would differ on each island throughout the Galapagos. It was Charles Lyell’s Principles of Geology that would let Darwin see nature in a fluid and dynamic new light. On the voyage back to England, his ideas about organisms changed as he started writing about the “undermining of the stability of species” (p. 27). 

     Back home, Darwin had assembled a vast amount of support for his theory of evolution even though he lacked the experimental evidence. His ideas ran counter to typical creationist ideology of the time and many skeptics were trying to poke holes in his theory. Ever since the publication of On The Origin of Species, scientists were attempting to scientifically demonstrate natural selection. Evolutionary studies now not only confirm Darwin’s grand theory, but also suggest he “underestimated the power of it” (p. 9).

     Two of the most enthusiastic evolutionary scientists are Peter and Rosemary Grant. They began documenting speciation in Darwin’s finches in 1973. Year after year, they return to study the change in beak size of the thirteen species of finches. Through capturing, tagging, and careful analysis, they have provided experimental evidence that natural selection is not an uncommon process- nature is constantly scrutinizing.

     The finches’ beaks are specialized mostly for a single purpose. However, the Grant’s found that finches with different size beaks ate the same food on the island. They also discovered that two species of finches on the same island differ more in beak size than the same species on two different islands. After a drought hit the islands, these slight variations started to make sense. With many of the small seeds eaten up, the finches with the smaller beaks would starve. It was mostly the larger beak finches, magnirostris and fortis that would persist. These finches were able to break open the tough shelled mericarp to procure the seeds. By the end of the drought, only 1/7 of the finches were still alive and the surviving fortis were 5-6% larger than the dead ones. Due to many of the females dying during the drought, only 1/6 of the male finches would mate. The offspring’s beaks turned out to be 4-5% larger than before the drought. The less-than-a-millimeter variations in beak size would make the biggest difference in survival!

     The availability of certain seed sizes has been shown to shape the frequency of beak sizes in a given cohort. For example, there is selection for smaller finches when they are young. Large finches can’t eat the large seeds due to their soft beaks. Larger finches become more common only as the birds age. Natural selection is not the only force shaping Darwin’s Finches. Sexual selection can decide who mates and who doesn’t. Peter Grant’s graduate student, Trevor, found males with bigger territories and jet-black plumage tend to win more females. In the following four years after the drought, the finches had continued to grow in size due to sexual selection. However, there are trade-offs between natural selection and sexual selection. When one streams too far in one direction, it is opposed by the pull of the other.

     The rains eventually hit Daphne Major and Darwin’s finches bred like crazy. Over two thousand finches populated the island and overshot the carrying capacity. As a result, they started dying. To the Grant’s surprise, natural selection had forced the finches in the opposite direction. The large ones were dying and the small ones were selected for. This happened because small seeds were abundant and large finches had trouble finding large seeds.

     Part Two: New Beings On This Earth begins by discussing the presumed implications of hybridism in nature and between Darwin’s finches. First believed by Darwin to confer a disadvantage for a species, the Grant’s have documented the advantages of hybridism between the finches. After the flood, the hybrids have demonstrated a higher fitness than individual species. Introducing new variation into the gene pool allows the finches to adapt to their ever-changing surroundings.

     Another evolutionary process shaping Darwin’s finches is his principle of divergence. This process is described by competition between two subspecies or varieties that drives them apart, thus allowing each new species to specialize towards its own niche. However, most of the divergence of the finches has been due to their geographic isolation. Only when they later occupy the same island, competition drives them farther apart.

     Evolution also involves “invisible” barriers that keep species apart once they have diverged (p. 159). The Grants have recognized the use of different songs and a thorough visual inspection when courting. The finches will also use each other’s beaks to discriminate. After the drought, the female large cactus finches started mating with the males that give the opposite call. This had caused a split between the species, resulting in large beaks and short beaks. To the Grant’s surprise, this difference disappeared as the two divergent cactus finches started to cross-mate. Drought had separated the species, but random mating had brought them back together again. There is a process of fission and fusion at work that can keep an evolving species in the same place over a long period of time.

      In Section Three: G.O.D. the author first describes how DNA is used to study variation that leads to evolution of a species. DNA can mutate quickly under stress. The flood is thought to have caused the genes in Darwin’s finches to mutate, leading to a rise in variation and evolution.

      In the remaining part of this section, Weiner describes the consequences of human impact on evolution. One of which is the introduction of a species into a new environment. This can lead to rapid evolution. The English sparrow, soapberry bug, and haw fly are all examples of species that have evolved in different ways in a novel environment. On the Galapagos Islands, the stationary presence of humans has certainly caused disturbances in finch evolution. For example, finches on Santa Cruz are hybridizing more often and their hybrids are remarkable and odd. The long-term consequences for human-caused introductions on the evolution of species remain unclear.

     The use of pesticides has increased the rate of insect evolution around the world. Ironically, when humans intend to eradicate a species we drive its evolution in the opposite direction of our initial intention. Insects have dodged and evolved defenses & antidotes to keep their genes passing onto the next generation.

     Global warming is speculated to change the path of evolution in Darwin’s finches. The Grants say global warming undermines the process of fission and fusion. It is thought, three species of finches are likely to fuse into a single population. Or a new species could be created in only a century. We have already seen the effect of human driven evolution during the industrial revolution with white and black moths.

      The author concludes the book by touching on the evolution of despecialization. He describes the how the Cocos Island Finch specializes in the division of labor. It is not necessarily an expert at one task, but is an acceptable multitasker- they learn from watching their elders. Like the Cocos island finch, humans have despecialized, which has allowed us to control our environment, swiftly radiate, and become fully human.

      The Beak of The Finch is an outstanding book with many strong points. It is well researched, clear, and thoughtful. Jonathan Weiner spent an extensive amount of time in the Princeton’s Biology library, reading over 150 scientific papers on the Grant’s work in the Galapagos. Along with these technical reports, he compiled nearly 2000 other papers and books on evolution. The extensive bibliography pays homage to the amount of research that went into writing this book.

      The author strives to unravel the mysteries, misunderstandings, and implications of evolution. Toning down the scientific dialogue, he has second-handedly documented the process in action through the Grant’s remarkable study. Describing the process of evolution through story and example is key to making such an important subject available to everyone. The Grant’s work would not make sense to most people without a background in science or evolution unless put into a decipherable context. For example, their discoveries are published in scientific reports that aren’t directly available to most people. However, popular magazines, newspapers, and books are widely distributed and written for the average person. Popular science writing has bigger implications when one considers the importance of the integration and understanding of nature in our modern society. Living more harmoniously with the natural world can be an end in itself.

     The last section of the book changes course and brings humans into the picture. This is one of the most important transitions in the book. Many people view science as an external entity. By describing the dynamic relationship between humans and science, evolution in this case, the author opens our view to the processes of nature. Weiner illustrates how our actions have had a measurable effect on the evolution of species. We have done this by introducing new technologies into nature, using nature for our ends, and misunderstanding the link between cause and effect. Humans are not separated from natural processes and we remain both the sculptor and the sculpted.

      With so much to praise about, there is little room for weak logic or style in The Beak of The Finch. Yet, the reader should be cautious that this book was first researched in 1990 and published in 1994. Science has progressed at breakneck speed during the last twenty years. This is not to say the logic, science, and conclusions are outdated; everything about evolution was spot on. There have been huge leaps in understanding how evolution works, especially at the genetic level. This is mentioned in the last section, but by the depth of the topic, one could still claim that evolutionary genetics hasn’t reached its potential. New technology has allowed scientists to conduct more vigorous and revealing experiments that have shed light on evolutionary processes. This book tells an awesome story and is an excellent read for an introduction to evolution. However, those who seek more depth and knowledge of current advances in evolution would do best in an updated textbook. Despite this, the Grants are pioneers and have opened up many new areas of research. Their work should not be pushed under the table as evolutionary science progresses.

      I would certainly recommend The Beak of The Finch. I am an avid evolutionist and want to open people’s eyes to the magnificent force that drives life. Scientists or not, it is crucial that we acknowledge the importance of Darwin’s finches as the beginnings of his impressive theory and as the model organism for studying evolution in action. There are many people who are not familiar with the basic underpinnings of evolutionary processes. The book is written in a way to address this discrepancy. The Grant’s have demonstrated Darwin’s testament, and the author effectively narrates this story of evolution.  After reading The Beak of The Finch, I am certain others will see evolution in a way that Darwin and the Grants have.