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Chapter 14
Themes
Key
LitCharts assigns a color and icon to each theme in The Beak of the Finch, which you can use to track the themes throughout the work.
Natural Selection and Evolution as Ongoing Processes
Nature and Humanity
Evolution, the Modern Era, and Nature’s “Resistance Movement”
The Interconnectedness of Species and Ecosystems
Hybridization and Specialization
Summary
Analysis
On the floor below Princeton’s Natural History Museum is a drab basement corridor which leads to a subbasement—there, the Grants keep a Galápagos archive, containing hundreds of vials of the blood of Darwin’s finches. In his day, Darwin imagined a secret code that might be used to explain what determines the variations of species—today, of course, biologists and evolutionists recognize this secret code as a being’s genes.
This passage, once again, shows how while Darwin had a spot-on hypothesis about the evolutionary process, he was constricted by his era’s technological limitations and unable to see it in action. But today, researchers can actually examine how the physical forces of selection and hybridization change an animal or plant’s internal code, as well.
Themes
Weiner watches as Peter Boag extracts DNA from frozen finch blood, bathes the DNA in an enzyme solution which fragments the DNA, and then transfers the fragments into a nylon bag. Boag is just one of many former finch watchers to “go molecular”—in other words, his research now focuses on DNA. Once Boag X-rays the DNA, he will be able to zoom in on small fragments that interest him—he is one of the first people to look at the DNA sequences of Darwin’s finches.
Peter Boag is a former field researcher who has narrowed his focus. His interest in the finches’ evolution has brought him to the forefront of a new filed—one in which he can look on a much closer level at the exciting changes taking place in the finch populations from year to year. This passage suggests that this kind of research is essential—in other words, the kind of work Boag is now doing supplements and enhances the work the Grants and other field researchers are doing.
Themes
A Galápagos finch has about 100,000 genes—about the same number as a human being—and those genes are spelled out in a total of roughly 1 billion letters. Only four letters make up the sequence: G for guanine, A for adenine, T for thymine, and C for cytosine. The finches’ genes are not fixed—they are shuffled and cut in each generation like a deck of cards, and each finch is completely unique. Mutations in the genetic sequence lead to variation: a mutation might cause cancer, or it might confer a small benefit on the finch, allowing it to survive and pass that favored mutation on again and again. Boag looks for slight differences in the sequences of letters that make up the birds’ DNA.
The physical expressions of mutations are seen, for example, in the finches’ changing beak sizes and shapes from generation to generation. But it’s the finches’ DNA that truly holds the answers to which mutations are happening and when. By zeroing in on these mutations, researchers can learn more about why some mutations or changes are advantageous, while others are life-threatening liabilities.
Themes
Evolutionists can learn more about “the lost history of life” from studying DNA. They can discover which animals are related, and how. Just as historians can now backdate Darwin’s manuscripts based on spelling errors he made at certain points in his life, biologists can sort out how Darwin’s finches have changed and when the most major changes took place. The finches that look most different—for instance, warbler finches—are those that have been evolving for the longest. Mutations spell out the answers to when certain species began to diverge—but because genes are like manuscripts that are being written and revised constantly, there are still many answers that evade Boag and his team.
Observing animals and plants in the wild isn’t the only way to learn about hybridization, change, and evolution: looking at a species’ DNA can reveal a lot about the specific, small changes they go through. And this is especially the case in a population that’s changing so quickly and so constantly.
Themes
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In times of stress, species like bacteria have been observed to start evolving wildly—it is a kind of SOS response, increasing the chance that at least a few cells will gain the variations necessary to survive the changing environment. This same response has been seen in plants—and many evolutionists, including the Grants, believe that the same thing has happened (and is now happening) to Darwin’s finches. A major event seems to be taking place.
By spreading out the gene pool, intercrossing, and multiplying quickly, a species’ variability increases—and this increases the likelihood that none of the species’ gene pools will run too low. It is a careful and ingenious stress response, and it ensures that as the forces of selection move through a population, the fittest will be spared.
Themes
