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The elite six boreal tree species

It was only when I discovered that a tiny handful of tree species make up the treeline that I began to see that an attempt at description might be possible. An elite club, the six featured here are the familiar markers of the northern territories: three conifers and three broadleaves evolved to survive the cold. Moreover, remarkably, each of these tree species has made a sectio of the treeline its own, outcompeting other species and anchoring unique ecosystems: Scots pine in Scotland, birch in Scandiavia, larch in Siberia, spruce in Alaska, and, to a lesser extent, poplar in Canada and rowan in Greenland.

But now the planet is hyperventilating

But now the planet is hyperventilating. This bright green halo is moving unnaturally fast, crowning the planet with a laurel of needles and leaves, turning the white Arctic green. The migration of the treeline north is no longer a matter of centimetres per century; instead it is hundreds of metres every year. The trees are on the move. They shouldn’t be. And this sinister fact has enormous consequences for all life on earth.

The treeline is a moving target

The fact that in modern usage the term ‘treeline’ has come to mean a fixed line on a map indicating the growing limit of trees is simply evidence of the very narrow time horizon of humans, and of how much we have come to take our current habitat for granted.

The prevalence of insignificance makes postdocs perish like fruit flies

Significance arises only where a relationship is not due to chance. In these cases, the null hypothesis is refuted and an alternative hypothesis vindicated. Impotantly, the null hypothesis does not need to be proved; it is only refuted trough expriments demonstrating significant results. […] The fact that the overwhelming majority of results are insignificant proves the wisdom of the presumption of chance. The prevalence of insignificance also explains why postdocs end up perishing like fruit flies rather than publishing.

Scientists are supposed to presume the null hypothesis

The trouble is that biologists consider function rather than neutrality as the default state. They presume significance - selection - rather than chance, which in this case is mostly drift. This stance is unscientific. Scientists are supposed to presume the null hypothesis, which roughly postulates that every relationship is the result of chance unless proved otherwise. The burden of proving significance weighs on the scientist except in evolutionary biology, where significance is the starting point. In this field, the burden of proof lies with whoever argues that chances determines the emergence, morphology, and size of a particular trait.

Generality is the signal and uniqueness the noise

Fundamentally, neutraity helps us keep our attention on the case that matters most, which is the general case. Aristotle described the proper focus of science when he aserted that “the universal is more important than the perception of particular cases.” Yet biologists obsess over uniqueness, hence Romanes’s unheeded admonition that specific characters - traits that distinguish a species from its nearest relatives - are precious to taxonomists but may well be useless for the organisms themselves. The traits on which species boundaries are based need not be useful; the need only be nonlethal. Indeed, as I detail in Chapter 7, the most useful traits tend to be those shared by many species, those that have proven their value to survival and reproduction across geological time and thus have persisted through bottlenecks. Generality is the signal - the selected - and uniqueness the noise. For evidence, we might look to our own eyes and genomes and fingerprints. Every human iris has its special patterns of colors, every genome its unique contents, and every fingerprint its singular topography of ridges and valleys. These signatures are useful to criminal investigators and designers of biometric passwords; they are biological indicators of the individual and no one else. All useful traits resemble each other; each neutral trait is special in its own way.

Nineteen tails in a row may still be due to chance?

The textbook example of the null hypothesis is the flip of a coin. Each coin flipped has a fifty-fifty chance of landing on heads or tails. According to the law of large numbers, one has to repeat the flip many times in order to achieve the expected 1:1 ratio of heads to tails. How many times? The consensual number, twenty, was theorized by the statistician an geneticist Ronald Fisher. According to Fisher’s significance level, nineteen tails in a row may still be due to chance, but twenty signifies a loaded coin. In experimental science, results obtained twenty times are said to be signfiicant, refuting the null hypothesis.

Something is wrong here with the math, isn’t it? Under the null hypothesis, the probability of having nineteen tails in a row is $(1/2)^{19}$, which is much smaller than $0.05$. So we would already reject the null hypothesis. Actually $2^5=32>20$, five tails in a row would be enough to reject the null hypothesis. That does not sound right either.

Aversion to neutrality is also embedded in language

Aversion to neutrality is also embedded in language. In Enlish, neutrality is expressed through the cancellation of other states. One may be nonaligned, disinterested, detached, unbiased, asexual, indifferent, or impartial. In this way, neutrality is coded as exceptional rather than normal. The normal state is one of preference or tendency, and neutrality is its negation. Linguists would describe neutrality as marked, which is to say uncommon, while the absence of neutrality is unmarked.

A universal theory is dubiously derived from an extreme case

If archipelagos are not nature simplified but rather nature in exceptional form, then the Galápagos is the exception to beat all others. Although situated in an equatorial region, the Galápagos archipelago has an exceptionally harsh climate. It is a kind of tropical desert - nothing like lush mainland Ecuador. Darwin notes in his Journal of Researches, “This archipelago, instead of possessing ahumid climate and rank vegetation, cannot be considered oherwise than exremely arid.” In average years, only the highest altitudes of the larger islands receive enough rainfall to support tropical life. The littoral and inland areas of the islands are classified as “arid” and “very arid” and are covered by brown and gray vegetation. Rainfall also varies considerably with altitude, between islands, and over time. Such conditions foster competition, the backbone of natural selection. One millimeter of beak length might be a question of life and death on the Galápagos’s lava, but two meters of neck length are negligible in the African savanna. A universal theory is dubiously derived from such an extreme case.

The Galápagos archipelago is unique

The finch, it turns out, is a good model for the study of natural selection, but this does not mean that the evolution of its beak followed a typical, much less unbiquitous pathway.

The same is true of the archipelago itself. While the islands offer a fascinating natural laboratory for the study of natural selection, they cannot be said to represent earth as a whole. The Galápagos sparked Darwin’s imagination, and righly so. But preserving that spark meant ignoring the unusual character of the islands - their climate, topography, and isolation - as well as conflicting evidence from the islands and other terrains he visited. Darwin wore his blinders so tightly that with the help of the domestication analogy, he was able to see in the ecology of the Galápagos confirmation that nature everywhere breeds the best. That myth persists to this day, though its result is somehwat unusual. Whereas myth typically emphasizes the extraordinary, in the case of the Galápagos, it does the opposite: it deprives the islands of their uniqueness. The myth renders the Galápagos ordinary, so that the ramarkable works of nature occurring there seem common to the whole planet.