Amidst all this, I finally had time to finish Jonathan Weiner's splendid The Beak of the Finch - a rich book detailing the work that evolutionary biologists Peter and Rosemary Grant have done on the Galapagos Islands. They have observed Darwin's theory of natural selection play out again and again and, in some cases, even observed how new species evolve, by watching the islands' famous finches.
It is the twenty-fifth of January, 1991. There are four hundred finches on the island at this moment, and the Grants know every one of the birds on sight, the way shepherds can tell every sheep in their flocks. In other years there have been more than a thousand finches on Daphne Major, and Peter and Rosemary could still recognize each one. The lock was down to three hundred once. The number is falling toward that now. The birds have gotten less than a fifth of an inch of rain the the last forty-four months: in 1,320 days, 5 millimeters of rain.Aside from the pleasure of his lucid writing, Weiner elucidates the development of Darwin's own thinking as well as integrating his original work with that of contemporary scientists observing the forces of evolution in action. This book makes plain the great theory's relevance to the natural world in which we live and also reveals the unbelievable drudgery of painstaking observational field work. Holy cow. Months upon successive months on a small hot island of rock and guano, measuring finch beaks and seeds per square meter of island.
The Grants, and the Grants' young daughters, and a long line of assistants, keep coming back to this desert island like sentries on a watch. They have been observing Daphne Major for almost two decades, or about twenty generations of finches.
Peter Grant combined the measurements of seed size and seed hardness and rated each kind of birdseed as the finches might themselves, in a sort of Struggle Index. The small soft ones of Portulaca score lowest on this index, only 0.35. The big hard seeds of Cordia lutea score highest, almost 14. Any of the finches can handle Portulaca in its beak, but very few are up to Cordia.Seed hardness and beak size are important because, in certain environmental situations the length of a beak determines how much food a finch can access to get it through a dry season and a miniscule difference in size is literally the difference between living and dying in these cases. As Weiner so emphatically puts it:
The Grant team also kept a census of the numbers of each kind of seed on the lava. To do this objectively they used a random-number table to select a single plot of lava, one meter square, somewhere in each grid. Then they counter every single fruit and seed they could find on that square of lava, whether it was dangling from the top of a cactus tree or lying in the middle of a cactus patch. Next they chose a much smaller plot within that square meter, again at random, and they sifted the hot cindery soil, collecting every fruit and every seed they found. Finally they withdrew to their tents and spread out their trophies on white trays to count one by one. And they repeated the whole routine fifty times...
"People think fieldwork is so romantic," Boag says, "but a lot of it is real slog. This was absolutely the worst."
...the birds were not simply magnified by the drought: they were reformed and revised. They were changed by their dead. Their beaks were carved by their losses.But I have to say, my skin shrivels up just thinking about the work they did. Then again, the Grants might think the same of my measuring the brainwaves of 6 year old children. Weiner conveys the passion the Grants have about their data and the great satisfaction of seeing such painstaking collection and patient calculation yield a story, otherwise their slog would be the reader's as well.
The isolated Galapagos archipelago precipitated Darwin's theory because they hosted many unique creatures that clearly bore a resemblance to relatives on the South American mainland and a fossil record of extinct relatives of those living forms existed
to help reveal a Law of succession that links the living to the dead, the same law that links the fossils of one stratum of rock to the fossils in the strata below...Of course, the story of Darwin's monumental deduction has been told again and again. What is different about Weiner's book is that he observes contemporary scientists, the Grants, as well as their students, many of whom develop into credible scientists in their own right, collect the evidence needed to confirm the original hypotheses. The argument has been made time and again against evolution that the workings of natural selection and sexual selection cannot be observed, that the processes necessarily takes thousands of years and so one is left only being able to infer it from the trail of fossils left behind, as Darw.in did. They also argue that it is impossible to make quantitative predictions based on data in nature, i.e., "proof" is not possible. However, both of these statements are incorrect. The lifespan of many species is short enough to observe the infinitesimal changing of the frequency of a particular feature across a species in response to both the physical characteristics of the environment they inhabit and the amount of competition they face from similar other creatures, and how these small variations can diverge into new species under certain conditions. This is exactly what the Grants's work with finches as well as Endler's with guppies reveals. Furthermore, the Grants have successfully made quantitative predictions based on their work, and over time have seen them to be correct. Weiner is particularly strong in making clear how this can result from an undirected process of random mutations in individual animals. Weiner's talent for writing about natural science is making that story as palpable as well as exciting to the reader.
"It was evident that such facts as these, as well as many others, could be explained on the supposition that species gradually become modified"
Weiner has a particularly good chapter on resistance, not only of certain ideological groups to teaching of evolution but also the resistance of moths or ticks to insecticide or E. coli to antibiotics. This is a particularly important part of the story, in my view, because it makes clear the ubiquity of evolution as it impacts our daily lives and the importance of seeing that a basic understanding of the process is gained in the general populace, as billions of dollars are thrown at developing insecticides and antibiotics when biology has clearly shown us that these are only temporary solutions. Bacteria and insects will not cease to evolve and eradication will not be achieved by these means. The target is always moving and these solutions are leading to more and more successfully resistant strains of streptococcus, tuberculosis, salmonella, pneumococcal pneumonia, and gonorrhea. We ignore the lessons of evolutionary biology at our own peril, so if you would like to read a book that depicts the mechanisms of this great theory via abundant example and does so in a style that feels very much like a good adventure story, I would recommend The Beak of the Finch by Jonathan Weiner.
Post a Comment