Darwin’s theory produced a complete break with previous ideas about natural life. We will touch on two points that are particularly important for the shaping of bourgeois ideology. The first is the end of teleology in science. As Marx put it: “It is here that, for the first time, ‘teleology’ in natural science is not only dealt a mortal blow but its rational meaning is empirically explained.”
The role of gradualism
Incredibly complex structures and behaviours are not the results of conscious efforts. God is no longer needed to understand the miracle of life. On the one side, this implies that human beings are not a special breed created by God but animals among animals as Huxley, for instance, noted in Man's Place in Nature underlining the fact that the human embryo is very similar to that of apes, etc. This means that religion had for ever lost its power to “explain” the world as we know it. That is why priests of any creed hate Darwin.
On the other side, however, Darwinism is used to prop up capitalism: an invisible hand works in nature as in society. And therefore any human intervention is useless. However, this transposition is baseless. All animals struggle to survive with the tools evolution has given to them. It just so happens that for humankind to survive our ancestors developed language, consciousness, cooperation, in a word, planning. The first humans started to differentiate from other bipedal apes exactly because they were able to plan: they planned hunting, they planned how to build their habitations, they planned ahead. They had too, in order to survive. To act with an end in sight is exactly what is specifically human. As Marx noted:
“We pre-suppose labour in a form that stamps it as exclusively human. A spider conducts operations that resemble those of a weaver, and a bee puts to shame many an architect in the construction of her cells. But what distinguishes the worst architect from the best of bees is this, that the architect raises his structure in imagination before he erects it in reality. At the end of every labour-process, we get a result that already existed in the imagination of the labourer at its commencement.”
Therefore, the immense progress produced by Darwin when he refuted a visible hand as cause of changes in the natural world does not mean that humankind is doomed to an anarchic society, that is to capitalism. We are aware of the laws of production. This is quite a difference from other animals.
The second point is that things change. Animals change, species are born and disappear. This aspect too was imported into social analysis, because it was useful to consolidate the idea of capitalism as a progressive system. The problem, however, is that if society evolves and nothing lasts forever, then capitalism too is doomed. Bourgeois ideology has therefore a contradictory relation with evolution. That is why they proposed an idea of history where evolution and even revolution was good until capitalism came into being, but no longer once it had been established. As Marx put it: “[the laws of capitalism] are eternal laws which must always govern society. Thus, there has been history, but there is no longer any”.
Capitalism is the end of history, of human evolution. The problem is that evolution never ends. Therefore, in allowing evolution into human life even under capitalism, they did so but as a gradual imperceptible modification of minor points of reality, because the fundamental pillars of society, that is the bourgeois ownership of the means of production with everything that flows from it should be hold as eternal. Gradualism is not a minor aspect of evolution that some scientists accept and other don't. It is the only way of reconciliating evolution and capitalism. That is why the role of Gould's theory is paramount, as we will see.
Bourgeois ideologists are not the only ones to have misinterpreted Darwinism. On the idea of the “struggle for life”, the ultra-left philosopher Pannekoek wrote that, “Darwinism is the scientific proof of inequality” and hence for him it was intrinsically anti-socialist. In his lack of understanding, he stated the following: “Socialism wants to abolish competition and the struggle for existence. But Darwinism teaches us that this struggle is unavoidable and is a natural law for the entire organic world. Not only is this struggle natural, but it is also useful and beneficial”. What, in effect, he was combatting was Malthus, or Social Darwinism, not the Darwinian theory of evolution.
By the way, ideological justifications for class inequality were nothing new; they can be traced back to the famous Apologue of Menenio Agrippa or even to Mesopotamian texts written sixty centuries ago. There is not a word by Pannekoek – on the contrary – about the little problem that struggle also means class struggle and that evolution could entail the overcoming of present-day natural as well as social structures. That is why – in spite of the attempts to use the theory of evolution to the advantage – Darwin, Huxley etc., were hated by the reactionary cliques of their time.
As for gradualism, the most famous theoretician of the Socialist International, Karl Kautsky, accepted gradualism because it fitted with his own reformist outlook of social evolution. This was not by chance. Just as capitalist ideology can accept evolution only within the straitjacket of gradualism, the same is true for reformism, that is the ideological reflection of bourgeois power inside the workers' movement. Thus, slowly, gradually, without a revolutionary break, capitalism becomes socialism, just as a species transforms into another. In reality this does not happen either with species or with societies. Once again, we see how a scientific refutation of gradualism is fundamental and Gould achieved this brilliantly.
The rise of the paradigm
The Darwinian research programme the dominated natural science in the XX century is defined as the “Modern Synthesis”, a name that suggested the fusion of the central core of the Darwinian theory – casual variation and natural selection – with the knowledge of genetic population that arose in the 1930s.
For the first time evolution was enriched with a full comprehension of the mechanisms by which variation and inheritance emerge. In the time that separates the publication of the Origin from the rise of the Modern Synthesis, biology eventually understood that traits of both parents are transmitted according to precise mathematics laws, elaborated by Gregor Mendel, the father of modern genetics. The consequences of this were huge: traits developed by the parents during their lives were not transmitted and the evolution of animals and plants was not the consequence of a simple adaptation to the needs posed by the environment, based on the use or disuse of organs. On the contrary, it confirmed that the mechanism worked the other way round: the environment selects randomly produced modifications.
On this basis Darwinian theory became a paradigm of a sort of omnipotence of natural selection: traits, adaptations, behaviours are directly shaped by natural selection. This paradigm was embodied by the Modern Synthesis: Ronald Fisher, Sewall Wright, Theodosius Dobzhansky, Ernst Mayr and George Gaylord Simpson were the main protagonists of this fruitful research programme that, over a period of 40 years, transformed the theory of evolution from being a viable hypothesis to an incontestable scientific fact. Each of these scientists gave a strong contribution in different fields of evolution.
In his famous work The genetical theory of natural selection, Fisher proved that the genetic basis of evolution could be extended to those traits, such as height, that do not appear to be transmitted in a Mendelian manner. In fact, until then scientists thought that traits like height could not depend on specific genes like the hair colour. Fisher showed that it was not the case: genes encoding for height work like the others, following the same laws. We can predict the transmission frequencies of the genes. This was the first success of the Modern Synthesis.
Sewall Wright developed Fisher's theory with the discovery of genetic drift. This mechanism is enriched by natural selection and shows the potential for random emergence (or disappearing) of a given characteristic with the passing of generations. In Wright's view, a population can be divided into sub-populations that gradually, through genetic drift, can colonize new areas and spread due to their “positive” traits. In other words, Wright's theory was a predictive mathematical model of the slow and gradual change embodied in the Modern Synthesis.
The great geneticist Theodosius Dobzhansky made an important step forward in our understanding of what a species is. In his most famous work Genetics of the origin of species, written in 1937, for the first time evolutionary biology gained a unifying definition of a species. This view was called the “biological definition of species” and it is based on the mechanisms of reproduction: a species is a group of individuals each fertile and reproductively isolated from other. In the words of Dobzhansky:
“Species are the smallest discrete groups of organisms whose free interbreeding with other groups is prevented by some physiological isolating mechanisms.”
Individuals of different species are separated by specific isolating mechanisms like incompatibility of genitalia, gametes, periods of fertility, sterility of the offspring etc. Yet in the words of Dobzhansky:
“(...) the production of hybrid offspring between two discrete groups may be prevented by a lack of sexual attraction between different individuals, by a physical non compatibility of the reproductive organs (genitalia or flower structure), by differences in the structure or physiology of the sex-cells, differences in the breeding seasons, and the ecologies of the parents. If produced at all, the hybrid may be too weak to attain sexual maturity, or be sterile because of the non-production of functional gametes” (Ibid.)
This theory greatly strengthened the core of the Modern Synthesis: i.e. that evolution is a slow and gradual process just as Darwin showed many years ago. Genes and genetics provide the mathematical basis of this theory and species are formed in the same way:
“It is only through the development of isolating mechanisms that different organisms may coexist in the same area, may produce new forms on which progressive evolution can be based, or differentiate and specialize to exploit the different 'niches' in the economy of nature” (Ibid.)
From these lines we can understand that the core of the Modern Synthesis was the extrapolation of the mechanism of micro-evolution to that of macro-evolution: in other words, the gradually changing of the gene frequencies over the generations, that is the basis of the formation of a new species, is also the basis of the formation of the superior taxa, like fishes, amphibia, reptiles, birds and mammals. There is only one mechanisms at work for the Modern Synthesis and the process evolves in a gradual manner. Everything we do not find in the fossils records is merely due to the difficulties in the process of fossilization.
George Gaylord Simpson's Tempo and mode in evolution, published in 1944, was the main work that explained this gradual interpretation of evolution. In this work, Simpson summarized the extrapolation of micro-evolution in the macro-evolution and underlined that most evolution proceeds through steady and gradual phyletic transformation of the whole lineage. This interpretation is named “anagenesis” or “phyletic gradualism”.
The Modern Synthesis was a great step forward for Darwinian theory. Its biological definition of species is still valid today even if scientists are suggesting and analyzing new ways of formation of species. The first cracks in the Synthesis, however, would not directly come from the genetic and biological mechanisms of formation of species but from the paleontological data and from the mechanism of geographical distribution of species.
 T. Dobzhansky, What is a species?, 1937.