A no less convincing response to the Bridgewater Treatises came at almost the same time as Vestiges and underlined the unfolding nature of science. This was the discovery of the great Ice Age, by Louis Agassiz and others. Agassiz was a Swiss geologist who later, in 1847, on account of his work on glaciation, was invited to Harvard. The original idea of a great Ice Age was not his: in 1795 James Hutton, in one of his rare instances of speculation, had wondered whether some strange, ‘erratic’ boulders near Geneva had been carried and left there by glaciers that had since retreated. But it was Agassiz who collected and collated the greatest mass of detail that put the issue beyond doubt. What Lyell did for the antiquity of the earth, Agassiz did for the Ice Age.
By observing present-day glaciers (of which there was no shortage in the Swiss Alps), Agassiz came to the conclusion that much of northern Europe had once been buried by a covering of ice, in places up to three kilometres thick. This conclusion (all the more remarkable because, at the time, he was more interested in fossil fishes) was based chiefly on three types of evidence found at the edges of glaciers even today – ‘erratics’, moraines, and tills. Erratics are large boulders – like those near Geneva – whose constitution is quite different from the rock all around them.58 They are pushed by the edges of glaciers, as the ice expands, and then left in a ‘foreign’ environment, when the earth warms up again and the ice retreats. Thus geologists suddenly find a massive boulder of, say, granite, in an area otherwise made up of limestone. Early geologists had thought that this type of phenomenon was produced by the Flood, but Agassiz showed that it was ice that produced this effect. Till is a form of gravel formed by the ice as it expands over the earth and acts, in J. D. Macdougall’s words, like a giant sheet of sandpaper.59 (Till provides a lot of gravel resources for modern construction industries.) Moraines are mounds of till that build up at the edges of glaciers and can be quite large: most of Long Island, in New York state, is a moraine more than 110 miles from end to end. Agassiz and others concluded that the most recent great Ice Age began about 130,000 years ago, peaked at 20,000 years ago, and ended quickly at 12,000–10,000 years ago. In time this would prove extremely significant, in that it tallied with the emerging evidence for the beginnings of agriculture.60 This provided coherence in both chronological terms and in respect of cultural evolution.
The term ‘evolution’ was originally used in biology exclusively for the growth of the embryo. In the original Latin it means ‘to unfold’. Outside that usage, terms like ‘progressionism’ or development were used to convey the cohering notion that simpler organisms had, in an as yet unknown fashion, given rise to more complex ones. Experts were divided as to whether this progression included man. Evolution was next used in a cultural sense, following the observations of Vico, Herder and others, who saw in the development of human societies a progression from more primitive to more advanced forms of civilisation. Peter Bowler makes the point that early anthropologists such as E. B. Tylor and L. H. Morgan argued that different races progress through a similar sequence of cultural phases, with peoples who are still ‘primitive’ belonging to ‘retarded lines of cultural development, held up at a stage through which the white race had passed at an earlier phase’.61
Lamarck was one of the most important advocates of progressionism. Jean-Baptiste de Monet, chevalier de Lamarck (1744–1829), was not quite the knave and fool he has sometimes been painted. It was he who noticed that some fossil species were analogous to creatures that are still living, which gave him the idea that some fossil lines, at least, might not be extinct, but instead had changed, responding to alterations in conditions on earth, and were therefore still living ‘but in an amended form that we don’t recognise’. This is a pre-Darwinian concept of adaptation.62 Lamarck was convinced of the great age of the earth and that life forms had continuously changed over long periods of time. And he considered man the end-product of this progression.63 Lamarck’s idea of evolution was two-fold. In the first place, he believed that nature embodied a principle towards increasing complexity. Second, he believed that organs within any creature developed more strongly the more often they were used and that these strengthened – or acquired – characteristics were passed on to later generations, always ‘provided that the changes acquired are common to both sexes, or to those which produce the young’.64
Because of these factors, and others, which we shall come to, it has been said that there was something ‘in the air’ in the middle of the nineteenth century, which helped give rise to what Darwin would call natural selection.65 A struggle for existence had been implied by Malthus, as long ago as 1797. Each tribe in history would have competed for resources, he said, with the less successful becoming extinct. ‘It is now known that in addition to Malthus, Darwin gained insights from reading the work of Adam Smith and other political economists. The concept of divergence through specialisation reflects the economic advantages supposed to accrue from the division of labour.’66 Another theory was advanced by William Charles Wells in 1813, ‘An Account of a Female of the White Race of Mankind’, where he suggested that the human races might have been formed when groups moved into unoccupied territory and where they were faced with a new environment.67 Accidental variations within the population would mean that some individuals would be better adapted to the new conditions, who would thus tend to become the parents of the new race.
Wherever one looked in the mid-nineteenth century, then, the role played by struggle, by competition, in society and in nature, was on everyone’s lips.68 It was by now difficult to contradict the evidence of the rocks, where the basic picture was clear. ‘The earliest rocks [600 million years ago] yielded only the remains of invertebrates, with the first fish appearing only in the Silurian [440–410 million years ago]. The Mesozoic [250–65 million years ago] was dominated by the reptiles, including the dinosaurs. Although present in small numbers in the Mesozoic, the mammals only became dominant in the Cenozoic [65 million years ago → the present], gradually progressing to the more advanced creatures of today, including the human species.’69 (The dates in square brackets were not, of course, accepted in the nineteenth century.) It was hard for people not to read some sort of ‘end’ in this progression, ‘leading’, via stages, to humans, ‘and thus revealing a divine plan with a symbolic purpose’. In books of the time, most ‘trees of life’ showed a main stem, thicker than others, leading directly to man.
This picture, of course, now has to be revised in the light of James Secord’s recent work. In his book, he provides an illustration of Darwin’s notes, made when he was reading Vestiges in the British Museum Reading Room. Darwin was far from impressed by many aspects of the argument (he never bought his own copy of the book), but Vestiges, coming on top of the ‘something in the air’, clearly had an effect in allowing Darwin to sharpen the distinction between his own theory of natural selection and its competitors.70