The Beak of the Finch: A Story of Evolution in Our Time

“The Origin of Species says very little about the origin of species.  [...] Darwin talks about the breeding of pigeons. He talks about Malthus, fossils, patterns in the geographic distribution of flora and fauna. He marshals an enormous mass of evidence that evolution has happened. Yet Darwin never saw it happen, either in the Galápagos (where he spent only five weeks) or anywhere else.”

The origin of species (or the cause(s) of speciation) becomes a driving question in The Beak of the Finch. Weiner introduces the question casually, by way of an ironic observation that the title of Darwin’s book on evolution did not quite capture its content. This short passage is the first of many to highlight the difficulty of studying evolution, considering that even the theory’s founder did not witness it in action. It adds another level of meaning to the Grants’ study, casting the Grants as Darwin’s intellectual heirs who come closer to witnessing the process than he ever could.

“After dark, they can sit on thrones made of relics of several shipwrecks apiece and lashed together with bits of string and read the Origin by candlelight. And a single black male finch sits at the top of a cactus tree giving out long, repeated whistles, very lonely and melancholy. Before going to bed they sometimes look up and see great frigatebirds like black angels silhouetted against the moon.”

Weiner’s vivid visual description compellingly dramatizes this story of a scientific research study. The evocative prose in this quotation depicts the romantic and bleak landscape on Daphne Major. It emphasizes the isolation of Daphne, suggesting an almost supernatural displacement from the concerns of modern life. Through Weiner’s scenic writing, metaphors, and poetic turns of phrase, the island and its avian occupants accumulate symbolic meanings over the course of the book.

“In Linnaeus’s vast botanical collections, he did notice many examples of local plant varieties, variations on a theme. But in his system these varieties were not half as significant as true species. Local varieties were merely instances in which one of the Lord’s created species had come to be adapted to its particular neighborhood. By definition, this divergence from the original type had occurred since the moment of Creation. Thus, varieties belonged to time and to our mortal earth, whereas species were incarnations of the holy thoughts in the mind of God during the act of creation.”

This passage illustrates the theological tradition that influenced Darwin’s young life. Weiner explains the incompatibility of Karl Linnaeus’s taxonomic system and evolution, as the taxonomy was grounded in devotion to God’s will. Any challenge to the dominant view of species as divinely created forms would appear as a challenge to religious faith—a dynamic that persisted between evolutionists and creationists at the time of Weiner’s writing.

“Variation is both universal and mysterious, one of the deepest problems in nature, and for Darwin it was for a long time completely bewildering. He wondered why, if his thinking was right, we see any species at all. Why not a continuous spectrum from tiny individual variations right on up the scale to kingdoms? Why for instance do we find a vampire finch and a vegetarian finch? (An example that Darwin might have liked, if he had known about the vampires.) Why not a whole smooth series of omnivores between the two, with a perfect series of intermediate beaks? Why not a blur, a chaos, an infinite web or Japanese fan of continuous variations?”

In this excerpt Weiner uses rhetorical questions to explain the subtler nuances in the theory of evolution. He describes Darwin’s moments of puzzlement, allowing the reader to recognize where he got stuck and what solutions he proposed. The technique explains evolution at an accessible pace, in relatively simple terms, while at the same time characterizing Darwin as relatable and fallible, more of a diligent problem-solver rather than a genius recipient of epiphany.

“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 competitors never fight one another, and the only sound of battle is the occasional crack of a Tribulus seed. […] When times are hard, their lives depend on how efficiently they can forage for food—how little energy they can expend in getting how much energy in return. They are hungry, they are thirsty, and they are trying to keep their budget in balance. And as poor Mr. Micawber used to say, ‘Annual income twenty pounds, annual expenditure nineteen six, result happiness. Annual income twenty pounds, annual expenditure twenty pounds ought and six, result misery.’”

In this passage Weiner animates competitive dynamics among the finches using personification, explaining the birds’ energy expenditure in terms of a “budget.” This technique reinforces the sense of the finches as representative of certain qualities in humans: simultaneous toughness and fragility, tenacity, and will to survive.

“[…] but as the pieces fell into place, the Grants and their team began to understand that they had something worth watching. They would have to come back. The birds are exceptionally variable in their beaks. They are exceptionally sensitive to these variations. They pass on their variations with exceptional fidelity. Each of the requirements of Darwin’s process, each of the prerequisites for evolution by natural selection, is heightened in Darwin’s finches to an almost unnatural degree.”

This passage occurs at an early turning point in the narrative of the Grants’ study, as they realize that the evidence of evolution at work among Darwin’s finches warrants extended observation. In concise, rhythmic language, Weiner emphasizes the birds’ exceptionally ideal qualities as objects of study. Noting that their high usefulness for further study is “almost unnatural,” Weiner hints at a sense of fate or destiny surrounding the birds and their watchers, a motif he repeats and expands elsewhere in the book.

“The average fortis beak before the drought was 10.68 millimeters long and 9.42 deep. The average beak of the fortis that survived the drought was 11.07 millimeters long and 9.96 deep. Variations too small to see with the naked eye had helped make the difference between life and death. The mills of God grind exceeding small.”

The many Biblical references in Weiner’s text draw a loose parallel between religious concepts and evolutionary processes. Here he repurposes a Bible quote concerning divine retribution to scaffold a description of natural selection. The passage highlights the importance of small variations in determining which animals live or die; this moment holds significance because Darwin’s belief in the significance of variation is verified here by the Grants through measurement and observation.

“But on the desert island of Daphne Major, dead birds are commonplace. They are everywhere. The lava is always littered with wishbones and beaked skulls. Whole seabirds lie outstretched here and there as if still in flight, odorless and mummified like feathered pharaohs in the dry and desiccating heat. Each generation lies where it falls, and the next generation builds on the ruins of the one before. They hatch in a morgue, breed in a crypt, and lie down with their ancestors, as if here not only life but death too is asking to be watched. Evolution discloses a meaning in death, although the meaning is like some of the berries that Darwin tasted in the Galápagos, ‘acid & Austere.’ There is a special providence in the fall of a sparrow. Even drought bears fruit. Even death is a seed.”

Weiner employs heightened language to add perspective and pathos to the story of the finches, which, the book shows, may be the story of humans as well. Personifying the birds again and alluding to William Shakespeare’s Hamlet, Weiner contemplates the meaning in the finches’ deaths and the ways that a generation’s death provides the ground upon which the next generation takes shape. Reciprocally, Weiner likens human meaning-making to the diet of birds: Meaning is a bitter berry, and death, a seed, is a form of nourishment or a potential for growth.

“Wherever males court females, or females court males, whether the signals are a bright splash of color, as in guppies or red-winged blackbirds, or loud far-carrying songs, as in frogs and crickets, their broadcasts are always in danger of being intercepted by the enemy. Strong colors or loud calls can attract a mate from one side and a predator from the other. Every bullfrog calling in the night is in the dangerous spot of a Romeo calling out beneath the balcony of the house of Capulet. A few species have found ways to finesse this problem. Among fish, some wrasses change color only very briefly, to flash a sexual signal in dangerous waters—the equivalent of a sexy whisper, psst!”

Through numerous anecdotes of animal behavior, Weiner illustrates the mechanics of evolution. This passage encapsulates the interplay and occasional conflict between natural selection and sexual selection, two fundamental forces that contribute to evolution. He encourages identification with the courting individuals—asking readers to see themselves in the precarious passion of other living things.

“If you measure natural selection over the course of a whole generation you may miss the many slings and arrows that it has taken along the way, the conflicting pressures in the nest, in the first days out of the nest, and on the yearlings and the adults; or on the acorn, the green shoot, and the towering oak. Each stage of life may have experienced an intense episode of natural selection, and yet their effects may have obscured each other’s traces by the time the very last of the generation has shuffled off the earth. Species of animals and plants look constant to us, but in reality each generation is a sort of palimpsest, a canvas that is painted over and over by the hand of natural selection, each time a little differently.”

Throughout the book Weiner suggests alternatives to iconic images upon which many build their understandings of life. The study of evolution can reveal these alternatives, as it uncovers mechanics of life that were not previously understood. Evolving species change constantly, quickly, and multi-directionally; with the metaphor of the palimpsest, Weiner challenges the view of “species” as fixed forms, arguing that in all life, multiple forces of creation are continually at work and sometimes at odds.

“Having seen even this much from the rim of Daphne Major, we can no longer picture the story of life as slow and almost static, a world view for which the chief emblem of evolutionary chance is a fossil in stone. What we must picture instead is an emblem of life in motion. For all species, including our own, the true figure of life is a perching bird, a passerine, alert and nervous in every part, ready to dart off in an instant. Life is always poised for flight. From a distance it looks still, silhouetted against the bright sky or the dark ground; but up close it is flitting this way and that, as if displaying to the world at every moment its perpetual readiness to take off in any of a thousand directions.”

This excerpt elevates the finches to an iconic, symbolic status in the narrative. Weiner speaks not of “species” or categories but broadly of life itself, enfolding the reader in the project of seeing our world more accurately. By describing the finches’ movements and behaviors as an embodiment of the basic qualities of life, he invites the reader to see aspects of themselves in the image of the bird.

“The Grants have always assumed, with Darwin, that the offspring of their Galápagos hybrids must be relatively unfit. They thought the hybrids would be rejected, culled, weeded out by the hand of selection. So would the tendency to interbreed. The rare and peculiar tastes that lead to a star-crossed marriage would remain peculiar and rare. For if the products of these mixed marriages had any advantage in the struggle for existence, then the tendency to interbreed would be favored, and hybridization would become more common. And if it became common, and stayed common long enough, all of these species would fuse. They family tree of thirteen finches would taper to a single twig. Their celebrated beaks, their ingeniously varied tool kit, would become one beak.”

Unusual patterns of hybridization become an important focus of the Grants’ research during their sabbatical. Weiner introduces the subject here by walking the reader through the prevailing assumptions around interspecies coupling. He underscores the earlier point that species are not fixed categories, hinting at the vulnerability of their distinctive forms to dissolution, an idea that is explored in depth in the following chapters.

“‘Evolution is change in variation,’ Peter says. ‘By studying evolution in action we can better understand the variation.’ He draws a bell curve on the blackboard and then gestures, as if to lift the curve off the board into the air with his hands, trying to suggest to his students the dimension of time—coaxing the curve off the wall with his hands and warping it eloquently as it floats out into the air. ‘This is what we have to explain,’ he says, pointing at the curve on the blackboard. ‘This is variation. And its change through time’—pointing with his eyes at the path of the curve through the air’—is evolution.’”

Because the mechanics of evolution are complex, Weiner takes care to reiterate the concept in the words of scientists and experts. In this scenic passage in a classroom at Princeton, Peter Grant explains evolution to undergraduates, giving the reader another opportunity to grasp its fundamentals. This scene also touches on the book’s ongoing motifs: It highlights Peter’s vitality and enthusiasm for his subject, and it depicts evolution as invisible, mobile, and multidimensional.

“No wonder Darwin remembered the exact spot in the road for the rest of his life. It is an extraordinary vision. Natural selection literally organizes life. The process of evolution by natural selection works right up the tree, from individuals to varieties, varieties to species, onward and upward, branching and branching, always diverging, helping to create all the myriad life-forms on the planet. Whole lines die out as inevitably as individuals die out, but the result is always something new and alive: the tree grows. In this view natural selection is even more powerful than Darwin first imagined. It is both beautiful and terrible, an agent of creation and destruction, like the flaming sword at the gates of Eden, ‘which turned every way, to keep the way of the tree of life.’”

This passage follows Darwin’s sudden, powerful realization of the principle of divergence. The rhythm of Weiner’s writing brings the reader closer to Darwin’s thought process. With blunt sentences followed by language of branching growth, Weiner echoes the energy of epiphany and the emotional experience of realization. He concludes on the image of the flaming sword, demanding engagement as he illuminates the principle further.

“It is true that the thirteen species of Galápagos finches are things of the passing moment, like the bodies of the individual birds that make up each species, like the islands that are their home, and like the very planet that is the home of all these islands. But one of the most significant facts about bodies, islands, and planets is that while they last, they are real, distinct, and separate. True species are as real as bodies, islands, or planets, though what holds them apart is not as uniform or as obvious to the eye [...] ”

Much of The Beak of the Finch advocates for an image of life as fluid and ever-changing, rather than fixed. Here Weiner provides a counterweight to that point, acknowledging the integrity of individual forms as he emphasizes their transience. He finds similarity in vastly different entities: bodies, species, islands, planets. By questioning the borders between species, he hints at a broader curiosity about the interplay of isolation and connection at all levels of existence.

“The birds pass invisible messages back and forth, swapping genes as casually as good neighbors exchange recipes, tools, or limericks. They are secret sharers, communing on their long voyage, open to suggestions. Their lines come together and come apart, and in this way the birds are created and re-created, again and again.”

Employing a motif of invisibility, this passage playfully depicts the evolutionary process at work on the genetic level. This process of constant genetic exchange preserves the birds’ potential to evolve, even in the absence of observable physical change. Weiner describes the genetic relationships among the birds as a sort of folk ritual, personifying the birds again with familiar human terms.

“[Peter and Rosemary] see now how much mixing is going on all the time on Darwin’s islands, and how often fate seems to smile on the oddballs, which to their experienced eyes are very strange birds and queer ducks indeed. The Grants are wondering whether some of these mixed-bloods on Daphne Major could be ‘potential escapees,’ in Peter’s phrase, from the constraints that bind the genes of their kind; whether birds like these could be the beginning of a really new departure, ‘the starting point of a new evolutionary lineage.’”

In this passage Weiner explains an important thread in the Grants’ work, built upon a trend of increased hybridization in their data. They theorize that hybridization might lead to the creation of a new species—a possible answer to the mysterious question Weiner has examined from various angles. Rather than argue the hypothesis assertively, he introduces the idea as light speculation, maintaining its mystery; the metaphor of speciation as “escape” further dramatizes the Grants’ hypothesis, stoking the reader’s investment.

“The hybrids are passing their motley collections of alien genes throughout the quasi-separate species on Daphne. It is as if the finch watchers were collecting the manuscripts of not one but thirteen young voyagers, all of whom are still writing and still learning to spell, and many of whom are copying from each other, with sentences and even whole paragraphs and pages flying back and forth.”

By comparing genes and DNA to “invisible characters” and forms of writing, Weiner gives the reader access to what otherwise is a technical and esoteric field in evolutionary biology. This metaphor helps convey the process of evolution as a kind of story, albeit one that is chaotically written by many authors. The image of a wild and incomplete writing process also calls attention to the fact that evolution is ongoing, unfinished, and unfinishable.

“Today invasions on this scale are happening every day, and virtually every spot on the surface of the planet is being assaulted by varied, new evolutionary pressures. Invaders ride in the puddles of old car tires, the bilge water of ships, the pressurized cabins of airplanes; in suitcases, on pant legs, and on mud-caked shoe soles. These are Darwin’s old jelly-jar experiments replayed in earnest. The consequence is an intensification of Darwinian pressures not only in the Galápagos but everywhere we look.”

As part of a building argument about humans’ impact on the planet, Weiner focuses on the profound impact that any newcomer to an established habitat will have on its environment. Here, Weiner emphasizes that ecosystems across the globe experience an unprecedented number of visitations, migrations, and “invasions” due to human activity. Humans often cannot appreciate the scope of these events because they happen not only at a large scale but also invisibly, in corners and unseen crevices.

“The standard model of speciation requires geographic isolation. That has been the canonical pattern for half a century, and many evolutionists believe it is the universal pattern. But evolutionists are forever dividing and subdividing into schismatic sects, kingdoms of Either and Or. Do new species arise in archipelagoes, like Darwin’s finches, or do they arise among neighbors? Is the origin of species fast or slow? Is the mechanism natural selection or sexual selection? And so on. None of these questions really have to be framed either-or. It is almost a law of science: the more indirect the evidence, the more polarized the debate. Evolutionists sometimes catch themselves sounding like the Little-Endians and Big-Endians in Gulliver’s Travels, fighting tooth and nail over the proper way to crack an egg.”

In this passage Weiner illustrates patterns of dichotomous thinking within the field of evolutionary science. Weiner’s theme of constant flux as a basic truth of life highlights the limitations of human imagination. By pointing out the tendency toward binary thinking among scientists, Weiner also gently undercuts any perception that the book is an argument flatly advocating for science over faith, or evolution over creationism.

“About 1868, Wallace says, some of the shepherds actually saw the parrots attacking their sheep. ‘Since then,’ Wallace reports, ‘it is stated that the bird actually burrows into the living sheep, eating its way down to the kidneys, which form its special delicacy.’ The shepherds meanwhile declared war on the parrots, shooting them on sight. ‘The case,’ Wallace concludes, ‘affords a remarkable instance of how the climbing feet and powerful hooked beak developed for one set of purposes can be applied to another altogether different purpose, and it also shows how little real stability there may be in what appear to us the most fixed habits of life.”

This colorful and gruesome anecdote helps to undermine the prevailing view of species as fixed entities. Here, Weiner illustrates the mutability not of form but of behavior, as a species of parrot in New Zealand uses the characteristics evolved in a vegetarian lifestyle for a carnivorous purpose. This dark anecdote appears as part of Weiner’s building argument that human customs and behavior drive our domination of and potential destruction of the planet.

“These cells have evolved an appalling arsenal of weapons against penicillin and its large family of antibiotics. They have evolved anti-anti-biotic enzymes to match every antibiotic that is being thrown at them. All these chemical weapons and counterweapons, says Tomasz, ‘match one another as defensive and offensive weapons match in classical warfare: shield against the arrow, bazooka against the tank.’ There are now drugs designed to attack the bacteria’s resistance to antibiotics: anti-anti-anti-biotics.”

Nearing his conclusion, Weiner shifts his focus from Darwin’s finches to human beings and our relationships with the life forms around us—our attempts at settlement and control. Throughout Chapter 18, Weiner highlights the limitations of those attempts and the ironic failure of many human enterprises (such as pest control) to account for evolution. That failure has potential to cause great harm, as our ill-informed efforts ultimately strengthen our adversaries’ defenses in an escalating pattern reminiscent of an arms race.

“According to the fossil record, only five times in the past six hundred million years has there been such abrupt havoc in the biosphere. Only five times have so many twigs and branches been lopped from the tree of life at once. It happened at the end of the Ordovician period, at the end of the Devonian and the Permian, at the end of the Triassic and the Cretaceous; and now it is happening again. We are altering the terms of the struggle for existence: changing the conditions of life for every species that is coeval with our own.”

Weiner’s final chapters give a sense of increased velocity both in style and in content. Weiner is blunt and unromantic as he asserts that humans are changing and accelerating the course of all life on the planet. Here the statement functions as a sort of closing argument, an attempt to convince the reader of this truth after the presentation of copious evidence.

“Our minds and talents are variable for the same evolutionary reason as finches’ beaks are variable in the Galápagos: jack-of-all-trades, master of none. And what drives this radiation within our species is a process like character divergence. Though we may not think of it as Darwinian, we all feel its pressure, wanting and needing to do what we are made for—seeking the task for which we are most fit.”

Here Weiner makes sense of human consciousness in evolutionary terms, as a characteristic whose variability sustains human life. After many more general comparisons between the finches and humans, Weiner uses a more pragmatic comparison to explain the mysterious purpose of humans’ widely varying minds. He contextualizes a common human struggle to understand one’s purpose, the longing to know what we are here to do.