Natural Selection: Discovery or Invention?
Editor’s note: We are delighted to present a new series by Neil Thomas, Reader Emeritus at the University of Durham, “Natural Selection: Discovery or Invention?” This is the first article in the series. Professor Thomas’s recent book is Taking Leave of Darwin: A Longtime Agnostic Discovers the Case for Design (Discovery Institute Press).
Natural selection clearly cannot be accounted a scientific “discovery” in the same sense as, say, the discovery of penicillin, and Darwin himself would always refer to it as “my theory.” Furthermore, it was a theory about which he had many doubts, commendably enumerated in the sixth chapter of his Origin of Species. His attitude to his own work was altogether more nuanced and complex than is sometimes acknowledged by some modern legatees. In this series I will make an attempt to pin down the various stages which led to the formation of his famous theory. I start with a brief historical contextualization in which the work of Darwin’s predecessors is considered since those predecessors’ work represented the point of departure which Darwin used to launch his own contribution to the field.
Before Charles Darwin
The idea of organic evolution (in contradistinction to that of natural selection) had had a long European pedigree before Charles Darwin was born. What Charles’s grandfather, Erasmus, borrowing an old alchemical term, termed the transmutation of species, was a subject which had already exercised that determinedly materialist group of 18th-century French speculative thinkers whom history has dubbed collectively “les philosophes.” This group too had toyed with the idea of animals being able to “shape shift” over vast tracts of time. Julien Offray de la Mettrie, in his L’Homme Machine of 1747, argued that all animal forms had emerged from previous forms, so that the earthworm might be expected to transmute in time to become a more complex animal. Denis Diderot in D’Alembert’s Dream (1769) mooted the possibility of a creature evolving through habitual functioning into another form of life altogether, even toying with the physiologically illiterate idea that those humans not required to perform manual labour could eventually become just heads! Erasmus Darwin, in touch with such “advanced” European theorizing, put forward the scenario of life having emerged from the depths of the oceans and evolving into different species in response to a striving for perfection in different environments — this being the (erroneous) conception1 of biological adaptation he shared with Diderot and his French near-contemporary, Lamarck, who coined the term transformisme for such postulated transformations.
These earlier scientists and philosophers accepted that they were advancing theories rather than facts, and indeed their somewhat extravagant theorizing was regarded by some peers as, to use an early-19th-century term, a “crotchet,” a harmless but unfounded obsession lacking one vital ingredient, namely, the actuating mechanism or what the Victorians termed the vera causa behind their posited organic transformations. So that when in 1844 Robert Chambers wrote of physical transformations in similar terms in his Vestiges of the Natural History of Creation, astronomer Sir John Herschel objected that the author had not identified a vera causa for such organic shifts, a polite Victorian way of saying “You have no evidence to back your claims, Sir!’’
The Greek Background
In fact, despite the vivid speculations of the philosophes and Erasmus Darwin, evolutionary thought had not, in any substantive sense, moved on since the time of Greek antiquity. The Greek natural philosopher who stands at the very threshold of mankind’s speculations about its place in the universe, Anaximander of Miletus (611-547 B.C)2, taught that the earth was originally muddy and that out of the primordial slime there arose what we would now term the denizens of the biosphere. First plants then animals then humanity emerged from their originally aquatic vivarium towards a new life on dry land (a conception which recurs in Erasmus Darwin’s Temple of Nature). For the Greek Epicurus and his later Roman follower, Lucretius, the problem of the world’s complexity was to be sought in different shapes and objects generated at random by the chance interaction of elements that Epicurus termed atoms. According to Epicurus/Lucretius, the origins of humankind are not to be sought in a primordial creation in some paradisal location (such as, in the Judeo-Christian tradition, the Garden of Eden). Plants and animals had simply evolved via an extended process of trial-and-error reminiscent of what Darwin would later term natural selection. Epicurus conceived of nature as an aggregate of material entities operated by blind and unvarying natural laws (without enquiring where such “laws” originated). For him Nature evolved spontaneously into more complex, emergent combinations, driven by contingent occurrences. Hence life and mind are not fundamental to the world but had allegedly “developed” as emergent properties of particular types of atomic configurations. Since the particular atomic constellations that constitute individuals originated by pure chance, species survive or die out according to their hereditary endowments, their fitness and reproductive ability.
This random process, which had continued over immeasurable tracts of time, was posited as having been responsible for the slow evolution of all Earth’s sentient species. In some cases that evolutionary journey had been unsuccessful, resulting in creatures not properly equipped to compete for resources or to create offspring, and which succumbed to extinction — in contradistinction to perfectly formed creatures able to adapt and reproduce. This idea antedates and in part anticipates the modern conception of the survival of the fittest, whilst the anti-theistic dimension of Darwinian speculation is anticipated in the Epicurean/Lucretian denial of the existence of that colourful array of Greek mythological characters (gods, fates, harpies, daemons, satyrs, et al.) claimed to have been spawned only by ancient mankind’s imagination and fear.
No Precise Theory
In none of this colourful speculation, either in Greek and Roman Antiquity or in 18th-century Europe, was any precisetheory put forward to explain the actuating mechanism behind all this organic development. Hence the much sought-after vera causa came to be seen as the Holy Grail of latter-day questers, that grand conceptual gap which history has told us was filled by the discovery of natural selection by Charles Darwin and Alfred Russel Wallace. They supposedly provided the consummation devoutly desired after more than two thousand years of vague speculation. In what follows I shall try to trace how this much-bruited “discovery” was actually arrived at.
Next, “The Evolution of Natural Selection.”
- The promulgation of Mendelism after 1900 showed that the habitual use of limbs had no effect on heritability, so that for instance the hypertrophic muscles of a weightlifter would have no effect on the man’s progeny.
- A clear conspectus of ancient and pre-scientific thought was provided in the older work by Philip Fothergill, Historical Aspects of Organic Evolution (London: Carter and Hollis, 1952).