Darwin’s theory certainly had a major weakness. There was no account of the actual mechanisms by which inherited characteristics were passed on (‘hard heredity’). These were discovered by the monk Gregor Mendel in Moravia in 1865, but Darwin and everyone else missed their significance and they were not rediscovered and given general circulation until 1900. Until the rediscovery of Mendel, the theories of the German biologist Auguste Weismann attracted most attention, in particular the idea of ‘germ plasm’, which he developed out of cell theory. It will be remembered that cells had first been observed following the invention of the microscope, when they had been called ‘globules’ or ‘bubbles’ (see here). By the early nineteenth century, when significant advances were made in the design of microscopes, biologists, following Marie-François Xavier Bichat, recognised twenty-one categories of animal tissue and realised that they were all made up of cells, now shown to consist of more than their walls and to contain a sticky ‘substance of life’, baptised ‘protoplasm’ by J. E. Purkinje in 1839.85 The men who finally showed that all plants and animals were made up of cells were J. J. Schleiden (plants, 1838) and Theodor Schwann (animals, 1839). Weismann noted the nucleus in cells and gradually came to the view that the germ plasm does not consist of whole germinal cells but is concentrated in the rod-like structures in the nucleus which, because they stained differently, were called chromosomes. But even when Mendel was rediscovered it was not immediately apparent that his mechanism in a sense ‘completed’ Darwinism. This is because a debate was then raging as to whether selection, if it occurred, operated on continuous variation or only on disparate variation, that is, characteristics (such as blue or brown eyes) that varied discretely or, say, height, that varied continuously. Mendel himself seems to have chosen discrete characteristics (flower colour, whether seeds were wrinkled or not) because they were cleaner examples of the theory he was trying to prove and because he had his own rival theory to Darwin, namely that selection acted on hybrids, on intermediate forms. (Hybrids traditionally posed a theological problem, as forms intermediate between divinely created species.) The full significance of Mendelian genetics for Darwinian selection was not recognised until the 1920s.86
Darwin didn’t stop with the Origin. No account of Darwinism can afford to neglect the Descent of Man. The idea of ‘progressionist evolution’ was everywhere in the nineteenth century, as we have seen, even in physics, with Kant and Laplace’s nebular hypothesis, the notion that the solar system has condensed from a vast cloud of dust under the influence of gravity.87
This is one reason why, as the sciences of sociology, anthropology and archaeology began to emerge in the mid-nineteenth century, they were united in developing within a framework of progressionism. As early as 1861, Sir Henry Maine, in Ancient Law, had explored the ways in which the modern legal system had developed from the early practices found in ‘patriarchal family groups’.88 Other titles with a similar approach included John Lubbock’s Origin of Civilisation in 1870 and Lewis Morgan’s Ancient Society in 1877, though the most impressive, by far, was James Frazer’s Golden Bough, published in 1890. Early anthropologists had also been affected by the colonial experience: on several occasions attempts were made to educate colonised populations, the aim being to convert them to the ‘obviously’ superior European cultural practices. The fact that these attempts had all failed persuaded at least some anthropologists that there had to be ‘a fixed sequence of stages through which all cultures develop’.89 And it followed from this that one could not, artificially, boost one culture from an earlier stage to a later one. Lewis Morgan defined these major stages as savagery, barbarism and civilisation, a comforting doctrine for the colonial powers. The main ideas he discusses are the growth of the idea of government, the growth of the idea of the family, and the growth of the idea of property.90
It was in this intellectual climate that archaeologists began conceiving the advances in regard to stone hand-axes that were described in the Prologue, when the ‘three-age system’ (of stone, bronze and iron) was introduced. We saw then that at first the idea of a ‘stone age’ of great antiquity met with fierce resistance. No one could accept that the earliest humans had co-existed with now-extinct animals, and it was only when Boucher des Perthes discovered stone tools side-by-side with the bones of extinct animals in the gravel beds of northern France that ideas began to change. But then, roughly speaking in 1860, thanks in part to publication of the Origin, there was a rapid evolution in opinion, and the much greater antiquity of the human race was at last accepted. Charles Lyell finally acceded to the progressionist view of the earth, then collected a mass of evidence in favour of the new view, and synthesised it in Geological Evidences for the Antiquity of Man (1863).
The extremely crude nature of the earliest stone tools convinced many that early man’s social and cultural circumstances were equally primitive, and this led John Lubbock to argue that there had been an evolution of society from savage origins. This was more shocking than it might seem because nineteenth-century religious thinkers still viewed modern man as degenerate as compared with Adam and Eve before the Fall. It was in his book Prehistoric Times (1865) that Lubbock first used the terms ‘Palaeolithic’ and ‘Neolithic’ to describe the transition from the Old to the New Stone Age, which he said could be distinguished by the change in use from chipped to polished stone, though more sophisticated variations were soon observed.91
For many people, the crucial issue underlying the debate as to whether man was evolved from the apes revolved around the question of the soul. If man was, in effect, little more than an ape, did that mean that the very idea of a soul – the traditional all-important difference between animals and men – would have to be rejected? Darwin’s Descent of Man, published in 1871, tried to do two things at once: to convince sceptics that man really was descended from the animals and yet to explain what exactly it meant to be human – how humans had acquired their unique qualities.
‘Although Darwin gradually abandoned his belief in a benevolent creator, he was certainly inclined to hope that the white race did indeed represent the high point of an inevitable (if irregular) advance toward higher things.’92 In the Descent, he knew that, above all, he had to explain the very great – the enormous – increase in mental power from apes to humans.93 If evolution was a slow, gradual process, why did such a large gap exist? This was the answer that the religious sceptics were looking for. His answer came in chapter four of the book. There, Darwin advanced the proposition that man possesses a unique physical attribute, the entity with which this book began, namely an upright posture. Darwin argued that this upright posture, and the bipedal mode of locomotion, would have freed the human’s hands and as a result we eventually developed the capacity to use tools. And it was this, he said, which would have sparked the rapid growth in intelligence among this one form of great ape.94 In the Descent Darwin did not offer any cogent reason as to why ancient man had started to walk upright and it was not until 1889 that Wallace suggested it could well have been an adaptation to a new environment. He speculated that early man was forced out of the trees on to the open savannah plains, perhaps as a result of climate change, which shrank the forests. On the savannah, he suggested, bipedalism was a more suitable mode of locomotion.