Saturday, June 13, 2009

The Origin of Species

Charles Darwin’s The Origin of Species is possibly the scientifically and intellectually most important book of the modern era. It was certainly the most important single book published in the C19th.

The theory of evolution was not remotely original to Darwin. Lamarck’s major work had been published in the year Darwin was born (1809) while his grandfather Erasmus Darwin had published on evolutionary theory—including the bases of what later became his grandson’s theory of sexual selection.

The Penguin edition includes a useful introduction by W. J. Burrows, which makes clear how important geology’s opening up the sense of the antiquity of the Earth was to development of Darwin’s theory.
As Burrows points out, such geology made science increasingly seem a weapon against belief since it undermined the religious view of the world as a recent creation where the ruins of Petra were half as old as time. The notion that science undermined religion was, at least in Christendom, something new. Clergymen-naturalists had looked at nature as a representation of the mind of God, a tradition with a long history in Christianity. C18th scepticism about religion had been based on moral objections and awkwardness about miracles. Geology opened up a time-frame nothing in religion had prepared folk for.

The Origin of Species is such a seminal work, the outlook it was arguing against seems remote. Darwin’s prime targets are the theory of independent creation and the doctrine of the immutability of species: positions that were religiously based but scientifically respectable. Darwin builds his case with layer upon layer of fact. His final chapters—on geographical distribution and classification—are particularly effective. Even now, almost 150 years after the book was published, they are delightful in their shedding of profound light on why the biological world is the way it is. So much of what Darwin wrote has been vindicated by subsequent science

Darwin builds his case methodically. He starts with variation (domestic followed by natural), then the struggle for existence, then the mechanism of natural selection, then patterns of variation, difficulties of the theory, then instinct, hybridism, the imperfection of the geological record, distribution of fossils in geological layers before bringing on the aforementioned discussions of geographical distribution and classification. Darwin concludes with a summary and recapitulation of his theory. A particularly appealing part of the book is Darwin’s description of his myriad, careful scientific observations and experiments.

Darwin’s theory of natural selection was famously based on Malthus’s principle of population. Darwin’s use of Malthus’ principle of population avoided a clear awkwardness in Malthus. There is none of Malthus’s geometric-increase-by-eaters, arithmetic-increase-by-eaten incoherence. All living populations can increase geometrically, it is the limitations of the natural world (sun, weather, moisture, extremes of hot and cold, seasons, etc) which generate the ultimate constraints. Within these constraints, the struggle for existence selects for advantageous variation that are then passed on to their descendants. In his words:
the Struggle for Existence amongst all organic beings throughout the world, which inevitably follows from their high geometrical powers of increase … This is the doctrine of Malthus, applied to the whole of the animal and vegetable kingdoms. As many more individuals of each species are born than can possibly survive; and, as a consequence, there is frequently recurring struggle for existence, it follows that any being, if it vary however slightly in any manner profitable to itself, under the complex and sometimes varying conditions of life, will have a better chance of surviving, and will thus be naturally selected. From the strong principle of inheritance, any selected variety will tend to propagate its new and modified form (p.68).
For there is no prudential restraint of marriage in nature (p.117) so
every single organic being around us may be said to be striving to the utmost to increase in numbers (p.119).
Darwin was a genuinely revolutionary thinker, and like many revolutionary thinkers, did not entirely grasp the implications of his own views. For example, writing of the movement of seeds by waterbirds,
Nature, like a careful gardener, thus takes her seeds from a bed of a particular nature, and drops them in another well fitted for them (p.378)
does not well convey the selective power of probabilistic processes.

Nor did Darwin grasp the significance of varying breeding strategies. He notes the existence of “slow breeders” but does not consider that a range of breeding strategies may be operating. To write:
of the many individuals of any species which are periodically born, but a small number can survive (p.115)
is putting it way too high. Many species do have lots of offspring and invest no care in their upbringing: of them Darwin’s comment is accurate. Others, however, have far fewer offspring and yet invest in their care: of them it is not. The former strategy typically requires little or nothing in cooperative behaviour. The latter often requires a lot. To regularly write as if the former is the way natural selection operates is to make cooperation far more problematic than it should be. Which was not good for either the scientific or the social implications of Darwinism.

Since Darwin rejects the notion of past catastrophes suddenly wiping out lots of species (Noah’s flood scientised), he has evolution proceeding at a consistent, gradual, but inexorable pace varying over time only with any variance in the rate of mutation. In order to drive this inexorable change, Darwin characterises the struggle for existence as relentlessly intense.

Which was to cause all sorts of problems. Even though Darwin was a very liberal and humane minded man (he detested slavery, for example and was horrified by the attempts to scientifically justify treating blacks as inferior beings), Darwin regularly used language that characterises the struggle for existence as bitter, unforgiving and relentless. Both Nazism and Marxism (especially Leninism) invoked Darwinian struggle to justify the sweeping away of inferior races or classes, as the case may be. And it was not a wild distortion of Darwin’s scientific rhetoric—however far from Darwin’s actual political and social views—to do so.

Darwin-the-careful-naturalist notes cooperation and slow breeding. Darwin-the-Malthusian-theorist makes the former problematic and the latter have no theoretical implications. Something can be both a great breakthrough and disastrously flawed.

As is seen, for example, his theory of sexual selection (only briefly touched upon in Origins [Pp 136ff]). For Darwin, sex is about exchanging semen. But he himself approvingly invokes more than once, the observation that
nature is prodigal in variety, though niggard in innovation (Pp 223,445).
Yet, Darwin deals with sex as if it only has this one purpose. If, however, one leaves more theoretical space for cooperation, then sex—as a way for animals to connect—would more clearly have various functions in nature beyond reproduction, which it clearly does.

But we, of course, have the advantage of that extra 150 years of observations, thinking, analysis and consequences. Origin of Species remains a towering intellectual achievement. We all live in its shadow.

Darwin is not a great writer. There are long sections where he seems to be trying to bury, even bore, the reader under sheer weight of details. But it is worth persevering with to understand, and enjoy, one of the great intellectual breakthroughs of human history.

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