Islands are an excellent place to study a lot of aspects of biology. Dispersal, competition, adaptive radiation, speciation, natural selection, on and on. They're isolated to various degrees, so it's somewhat easier to keep track of arrivals and departures. They're of relatively limited area, so it's easier to define the boundaries for a study.
Quammen looks at the history of studying life on islands as it influenced the development of the idea of evolution by natural selection by Alfred Wallace (and Darwin), and then how the study of that changed over time. Especially once MacArthur and Wilson developed their theory of island biogeography. Which said, in a simplified manner, that the number of species on an island will be based on a combination of its distance from the mainland and its size. Distant islands are difficult to reach, not many things can swim/float/fly that far. Small islands can't support as many species, because there's not as much space, and not as many habitats or ecological niches.
Operating from that, MacArthur and Wilson deduced there's a sort of equilibrium each island between new arrivals, and the extinction (or extirpation) of species already present. Where that point is on the graph depends on the islands size and distance. This is interesting enough on its own, or it was to me when I was talking biology classes in college. But it's become more relevant as human development and reshaping of the planet progresses.
As Quammen notes in the late stages of the book, even habitats on the mainland are becoming islands as the land around them is turned into Wal-Marts, or row of identical suburb housing. Missouri, for example, has about 1% of the tallgrass prairie it had before the Europeans showed up, and it's scattered all over the west side of the state, in little patches. 40 acres here, 120 acres over there, maybe a nice 3,000 acre patch on a conservation land.
While Quammen discusses all this, and the resulting battle lines that were drawn after The Theory of Island Biogeography was published, he's also traveling the world. Speaking to different biologists (including Edward O. Wilson, because this book was published in the 1990s) about their work, how it relates, what they're finding.
That can involve speaking with a biologist who discovered a previously unknown species of macaque in Madagascar, that's carved out a niche by eating parts of cane trees that are high in cyanide. Or traveling to the Amazon to a location where there are dozens of small patches of forest left behind from the clear-cutting, essentially islands surrounding by oceans of open land, where scientists monitor the species within to see how they're doing. How big a patch is enough to sustain a population?
Quammen's not a biologist by trade, and he's definitely not a mathematician, so he tries to avoid getting too technical when the topics he's discussing start veering into logarithmic math. Which is fine with me. I know the math part is important, but the Experimental Design course I took in grad school taught me I didn't grasp how people figured out the mathematical relationships that they build their formulas on.
Quammen's writing is very casual at times. full of his own opinions, and not just on his distaste for math. He's moderately scornful towards Darwin, who he's pretty sure delayed publication of a paper Alfred Wallace wrote and sent to him for review on evolution by natural selection, so Darwin could finally get off his ass and publish something about it first, after 20 years of nitpicking his writing.
He may very well be right, although I think basing it on best estimates of shipping rates from Indonesia to England in the 1850s is a little flimsy. But you have to factor it in when you read it. Quammen describes Darwin's writing style as 'half-barmy', but Quammen's the one who felt this book needed a four-page digression about him getting mugged in Rio and almost missing his bus out to meet a biologist studying muriquis. Outside a brief joke that the monkeys seem to behave more politely than humans in Rio, the story serves no purpose, and the book's over 600 pages, so it's not like it needed padding out.
What it could have used, was some diagrams. The book has several general maps, showing things like whatever island chain he's happening to visit at that point in the book, along with a few relevant towns marked on it. But seeing as this book is presumably written for people who aren't trained biologists, maybe some pictures would have helped. A copy of the graph MacArthur and Wilson made, or a diagram showing how adaptive radiation works. Something to illustrate the concepts. Hell, even some pictures of the creatures he's talking about wouldn't have hurt. I know what a Komodo dragon looks like, but I have no mental picture of an indri.
That aside, it's a neat book to read if you're at all interested in that sort of biology. And if the idea of these biologists sniping at each other like high school kids via research papers published in various scientific journals amuses you, well there's a fair amount of that in the second half.
'The crux of the matter of extinction - the extinction of Raphus cucullatus or any species - is not who or what kills the last individual. That final death reflects only a proximate cause. The ultimate cause, or causes, may be quite different. By the time the death of its last individual becomes imminent, a species has already lost too many battles in the war for survival.'
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