First cracks in the paradigm
After being generally accepted as correct, a theory passes through a period of questioning. This was also the case with the Modern Synthesis and the theories of punctuated equilibrium. From the 1930s to the 1950s, the dominant paradigm was strengthened by the discoveries of genetics: the paradigm of evolution based on gradually changing gene frequencies was reinforced by the works and the analysis of Fisher and Dobzhansky.
However, with the triumphs also came problems and a new interpretation began to emerge. In the aforementioned work of Simpson Tempo and mode in evolution, although it was an orthodox brilliant work of palaeontology of the Synthesis, it also proposes the idea that tempo and mode in which evolution proceeds are not the same thing. Above all, Simpson admitted that fossil records show us different rhythms of evolution. This idea, however, was ignored for many years by mainstream scientists.
Eventually, the first real crack in the paradigm was represented by Animal species of evolution, published by the ornithologist Ernst Mayr in 1963. Mayr was one of the most important evolutionary biologists of all time. He was a zoologist, a tropical ornithologist and, above all, the discoverer of the “allopatric theory of speciation” based on the data he had collected for many years as an ornithologist. This was a revolution in the way we consider how a species is formed. And Mayr was aware of the limitations of the Synthesis:
“As a consequence, geneticists described evolution simply as a change in gene frequencies in populations, totally ignoring the fact that evolution consists of the two simultaneous but quite separate phenomena of adaptation and diversification.”
In Mayr's view, a new species is formed by a geographic separation of a small part of population from the mother population: this small founder population colonizes a new environment and it can evolve more rapidly. After enough time, the founder population and mother population are no longer interfertile if they meet again. In the words of Mayr:
“The major novelty of my theory was its claim that the most rapid evolutionary change does not occur in widespread, populous species, as claimed by most geneticists, but in small founder populations” (Ibid.)
“(...) my conclusion was that a drastic reorganization of the gene pool is far more easily accomplished in a small founder population than in other kinds of population” (Ibid.)
This was an implicit negation of phyletic gradualism elaborated by Simpson. Allopatric speciation did not deny the biological concept of species of Dobzhansky based on isolating mechanisms and populations united by mutual fertility, but incorporated it into a new view, thus opening a debate: do new species arise from a population that changes or from small founder populations?
Punctuated equilibria: a revolution in biology
When Stephen Jay Gould and Niles Eldredge published Punctuated Equilibria: an alternative to phyletic gradualism in 1972, they introduced a new question: if Mayr's geographic speciation is true, what are the consequences for the speed of evolution? It was like a bomb exploding in the scientific debate. Gould and Eldredge reversed the Synthesis' view applying the geographic speciation of Ernst Mayr to the interpretation of the fossil records. As they explained:
“The theory of allopatric (or geographic) speciation suggests a different interpretation of paleontological data. If new species arise very rapidly in small, peripherally, isolated local populations, then the great expectation of insensibly graded fossil sequences is a chimera. A new species does not evolve in the area of its ancestors.”
This view on evolution leaves no room for missing links. Breaks in the fossil records reflect the actual geographic speciation over the generations. The fossil records show also the stasis in which founder populations found themselves after they adapted to a new environment. As Gould and Eldredge underline:
“The central concept of allopatric speciation is that new species can arise only when a small local population becomes isolated at the margin of the geographic range of its parent species. Such local populations are termed 'peripheral isolates'. A peripheral isolate develops into new species if isolating mechanisms evolve that will prevent the re-initiation of gene flow if the new form re-encounters its ancestors at some future time. As a consequence of the allopatric theory, new fossils species do not originate in the placed where their ancestors lived” (Ibid.)
In the theory of Gould and Eldredge, evolution proceeds from quantitative accumulation to qualitative leaps as is clearly recorded by the fossil records. It was a new way of reading the natural history of our planet: in other words, it gave a new tempo and new mode to evolution. Moreover, punctuated equilibria encompassed the previous theory of biological species and geographical species, not by rejecing them completely but by applying to these concepts a dialectical view. Small founder populations and different rhythms marked by fossil records: these are the ingredients of this revolutionary theory.
In the words of the two scientists:
“In summary, we contrast the tenets and predictions of allopatric speciation with the corresponding statements of phyletic gradualism previously given: 1) New species arise by the splitting of lineages; 2) New species develop rapidly; 3) A small sub-population of the ancestral form gives rise to the new species; 4) The new species originates in a very small part of the ancestral species' geographic extent - in a isolated area at the periphery of the range. These four statements again entail two important consequences: 1) In any local section containing the ancestral species, the fossil record for the descendant's origin should consist of a sharp morphological break between the two forms. The break marks the migration of the ancestral range. (...) 2) Many breaks in the fossil record are real: they express the way in which evolution occurs, not the fragments of an imperfect record.” (Ibid.)
After the publication of their first work, Gould and Eldredge were often accused of rejecting the core of Darwinism. On the contrary, they gave to it a solid foundation. The theory of punctuated equilibria is based on natural selection because geographical speciation and the biological theory of species are based on natural selection. The new conditions (such as the potential lack of predators in the new environment) in which a small founder population finds itself give a boost to the rhythm of change.
Gould and Eldredge explain that fossil records can actually reflect episodes of acceleration in natural selection as well as the stability of species for long periods of time. Many years later, on the basis of new discoveries in the mechanisms of evolution, Gould and Eldredge were to extend the Darwinian core of natural selection from populations to species. In fact, punctuated equilibria is incompatible with the extrapolation of micro-evolution to macro-evolution made by the Modern Synthesis: taxa formation from plants to mammals requires different mechanisms that are not reducible to micro-evolution that operates on populations. These mechanisms include natural selection, but they are not reducible to it. It is a pluralistic view of evolution based on a principle of emergent properties.
Dialectic and science
It may also not be irrelevant to our personal preferences that one of us learned his Marxism, literally at his daddy's knee – Gould
Within a few years, the theory of punctuated equilibria opened up a number of debates in palaeontology and evolutionary biology and proved to be a valid interpretation of the fossil record. For example, the traditional interpretation of the Modern Synthesis assigned too much time to the development of different phyla. Gould underlined this with irony:
“Thus, Durham tried to estimate the age of common ancestry for deuterostomes by stacking species end to end in lineages of phyletic gradualism. He specifies 6 m.y. as an average 'species duration' and estimates 100-600 durations strung on a line to reach the common ancestors of Early and Middle Cambrian echinoderms. Running further down the string, he places the common ancestors of deuterostomes 'slightly over a billion years before the beginning of the Cambrian' – an age considerably earlier than most generous estimates now being offered for the origin of the eukaryotic cell”
As we have noted, all scientists have an ideology that drives their work. The problem is they are not aware of it. Gould and Eldredge were conscious that they could never work out their theory without a specific conception of society. It is true that, over the years, Gould had reduced the political consequences of his theory in a situation where there was a general retrenchment by left-wing intellectuals. However, with this theory, these two scientists overturned the traditional view of evolution with a dialectical point of view. Gould and Eldredge always discussed the direct and indirect links between the dominant ideology and science. In 1981, Gould wrote one of his masterpieces entirely dedicated to this issue (The mismeausure of man). It is a wonderful example of how the dominant ideology can twist scientists' minds. But already in 1977 Gould and Eldredge emphasized that:
“The famous statement attributed to Linnaeus – natura non facit saltum – may reflect some biological knowledge, but it also represents the translation into biology of the order, harmony and continuity that European rulers hoped to maintain in a society already assaulted by calls for fundamental social change” (Ibid.)
In 1977 they paid a direct tribute to Marx and Engels that is worth quoting in full:
“Karl Marx, who admired Darwin greatly and once stated that the Origin contained 'the basis in natural history for all our views' made the same point in a famous letter to Engels (1862):
“'It is remarkable how Darwin recognizes among beasts and plants his English society with its division of labour, competition, opening of new markets, invention, and the Malthusian struggle for existence. It is Hobbes' bellum omnium contra omnes (war of all against all) and one is reminded of Hegel's Phenomenology, where civil society is described as a spiritual animal kingdom, while in Darwin the animal kingdom figures as civil society.'
“We mention this not to discredit Darwin in any way, but merely to point out that even the greatest scientific achievements are rooted in their cultural contexts – and to argue that gradualism was part of the cultural context, not of nature.
“Alternate conceptions of change have respectable pedigrees in philosophy. Hegel's dialectical laws, translated into a materialist context, have become the official 'state philosophy' of many socialist nations. These laws of change are explicitly punctuational, as befits a theory of revolutionary transformation in human society. One law, particularly emphasized by Engels, holds that a new quality emerges in a leap as the slow accumulation of quantitative changes, long resisted by a stable system, finally forces it rapidly from one state to another (law of transformation of quantity into quality). Heat water slowly and it eventually transforms to steam; oppress the proletariat more and more, and guarantee the revolution.” (Ibid.)
The role of Stephen Jay Gould
The entire life of Stephen Jay Gould as a scientist was spent in developing the Darwinian theories of evolution and in enriching them with a dialectical method. It is not possible to deal here in a single article with his whole contribution to science but we want to point out that he succeeded in exposing the dialectical character of nature not ideologically, but by finding this character in the way nature concretely is. Criticizing the poor results of Lassalle as a theorist, Marx said: “He will discover to his cost that it is one thing for a critique to take a science to the point at which it admits of a dialectical presentation, and quite another to apply an abstract, ready-made system of logic to vague presentiments of just such a system”. The punctuated equilibria theory is such an achievement, a theory that does not impose dialectics on nature but honestly concludes that it is impossible to understand evolution without dialectics.
Scientists cannot isolate themselves from society. Although many of them seem to survive with a healthy although rough realism, they are vulnerable to the ruling ideology. This is obvious: in a class society, as the control of science is in the hand of the ruling class. This involves control over funding, over education plans, over recruiting and careers, over information and the media. It is not by chance that the recent discovery of the Higgs' boson was used to speak about God (“the discovery of the God particle”) as if the two things were somehow linked. Similarly, the view of evolution based on gradual changes in the gene frequencies was used to push the idea that everything is determined by genes: social differences, poverty, unemployment, illiteracy and so on. Rich people do better because they are the fittest to rule just like the survivor species in nature!
However, while most scientists think they can do without ideological and political ideas, and others embrace the status quo, there are also thinkers that embrace Marxism as a result of their research. As Engels pointed out many years ago, science proceeds in a dialectical manner. The ruling class cannot accept this, as dialectics means revolution in nature as in society. The theory of punctuated equilibria, giving a fundamental importance to sudden change, that is to revolutions, in nature is a direct attack on the ruling ideology. This is absolutely clear to those bourgeois ideologists that try to downplay its importance and who vilify Gould and Eldredge for their ideas.
Revolutions are rare events in nature as in society, but they mark entire epochs. That is why the analysis of revolutions is the most important task of science, whether we are talking about the Earth, the animals or humankind. Stephen Jay Gould had the merit of understand this and of not being frightened by revolutions.
Thanks to him, our knowledge of animal evolution made a tremendous leap forward. As Marxists, we are proud of the fact that this was achieved precisely because he was influenced by Marxist thinking. Brave intellectuals are important in helping us understand the world we live in. The working class armed with revolutionary ideas is required to change it.
Darwin C., The Origin of species, 1859
Dobzhansky T., What is a species?, “Scientia”, 1937
Eldredge N., Gould S. J., Punctuated equilibria: an alternative to phyletic gradualism, Models in Paleobiology, 1972
Eldredge N., Gould S. J., Punctuated equilibria: the tempo and mode of evolution reconsidered, Paleobiology, 1977
Gould S. J., The Panda's Thumb, 1980
Grant E., Woods A., Reason in revolt, 1995
Mayr E., Speciational evolution or Punctuated equilibria, in The dynamics of evolution, 1992
Marx K., The Poverty of Philosophy, 1846
Marx K., Capital, 1867
Somit A., Peterson S. A., The Dynamics of Evolution: The Punctuated Equilibrium Debate in the Natural and Social Sciences, 1992
 E. Mayr, Speciational Evolution or Punctuated Equilibria, quoted in Somit and Peterson, The dynamics of evolution,1992.
 S. J. Gould and N. Eldredge, Punctuated Equilibria: an alternative to phyletic gradualism, 1972.
 S. J. Gould and N. Eldredge, Punctuated equilibria: the tempo and mode reconsidered, 1977.
 Marx to Engels, 1 February 1858 (http://www.marxists.org/archive/marx/works/1858/letters/58_02_01.htm).