Cause and effect in biology and history

Mayr’s book Toward a New Philosophy of Biology is filled with truly profound and fascinating essays. In “Cause and Effect in Biology,” he discusses the question of determinism and prediction in biology. The question is quite important, because a mechanistic interpretation of the physical world, which considers only physical or physicochemical causes and explanations, fails to really account for biological phenomenon (and other, higher, levels of organization, including social development). This leads generally to supernatural explanations for life—vitalism, spiritualism, religion, etc.

In the works of Descartes, one finds this relationship—between mechanistic materialism and spiritualism—expressed quite clearly. The body is a machine, according to Descartes, something akin to a system of water pumps. This obviously fails to account for the great complexity of biological phenomena, particularly mental experience, and the soul is postulated to account for what can not be explained by analogy to a simple machine. And the mechanistic worldview of Newtonian physics (or rather, the attempt to explain all of the material world in reference only to this physics) is in fact quite compatible with the most varied forms of religious obscurantism, and Newton himself embodied these two ways of seeing the world (he devoted as much time to Biblical exegesis as he did to the creation of the new physics).

Mayr quotes C. Bernard as declaring, “We admit that the life phenomena are attached to physicochemical manifestations, but it is true that the essential is not explained thereby; for no fortuitous coming together of physicochemical phenomena constructs each organism after a plan and a fixed design (which are foreseen in advance) and arouses the admirable subordination and harmonious agreement of the acts of life…Determinism can never be [anything] but physiochemical determinism. The vital force and life belong to the metaphysical world.” Indeed, to a certain extent this argument is cogent, i.e., if you accept the premises, then the conclusion more or less follows. However, the question is really whether or not physiochemical determinism accounts for the entire scope of natural law governed processes. Similar arguments are brought out by those who would seek to deny that there is a science of history—history can not be a science because it cannot have the sort of laws that physics has. Popper has made a variety of this argument in some of his writings. The social analogy of vitalism, the idea that there is a special “life force,” generally associated with the soul or some metaphysical entity, has its analogies in the historical sciences—the “great man theory of history,” and other varieties of historical idealism.

Indeed, the relationship between biology and the science of human history is deeper. Biology is a historical science. As the great evolutionist Dobzhansky reminded us, “nothing in biology makes sense outside of evolution,” that is, outside of history. The rise and triumph of evolutionary biology, beginning with Darwin and becoming firmly established during the first decades of the twentieth century with the “evolutionary synthesis,” revolutionized biology, placing evolution at its core and requiring all biological phenomena to be understood in the process of their historical development.

Mayr quotes the physicist Max Delbruck (“A physicist looks at biology,” 1949): “Any living cell carries with it the experiences of a billion years of experimentation by its ancestors.” That is, the biological entity—the cell, the organism, the species—is the product of a prolonged period of interaction between its ancestors and the surrounding world. To understand the entity, one must understand how it came to be, how its ancestors interacted and adapted to the totality of its organic and inorganic environment. For the purposes of categorization and experimentation, it can be abstracted from its historical and biological environment, but a truly concrete understanding of its nature comes only from cognition of this environment. Speaking more generally, Hegel once said that if one were to eliminate one speck of dust, the entire universe would collapse, by which he meant that the universe can only truly be comprehended as a unity of difference, and not as isolated essences.

In discussing cause and effect in biology Mayr distinguishes between two fundamental types of cause: proximate cause and ultimate cause. Among the proximate causes, one includes the physiochemical or immediate environmental factors that produce a biological event, e.g., the migration of a bird on a particular day. One might point to the temperature on that day, a certain neural state induced by the environment in the bird, etc. When one begins to explain the event in terms of the evolutionary heritage of the bird, its specific adaptations that have led it to migrate south when the weather turns cold, etc., then one is dealing with ultimate causes. “These are causes that have a history,” Mayr writes, “and that have been incorporated into the system through many thousands of generations of natural selection…[P]roximate causes govern the responses of the individual (and his organs) to immediate factors of the environment, while ultimate causes are responsible for the evolution of the particular DNA program of information with which every individual of every species is endowed.” The “purposiveness” of biological phenomena, which so impressed Bernard, is a product of these historical, ultimate causes.

In history, the proximate causes are those that deal with the particular individuals or political forces acting at a given stage of history—the assassination of the Archduke let the Austrian government to issue an ultimatum, sparking a network of alliances that led to World War I. The ultimate causes are those that refer to the deeper social forces at work—the rise of German imperialism, the conflict between the nation-state system of Europe and the globalization of the world economy, etc.

We come now to the problem of prediction in biology. According to Mayr, “The theory of natural selection can describe and explain phenomena with considerable precision, but it cannot make reliable predictions, except through such trivial and meaningless circular statements, as, for instance: ‘The fitter individuals will on average leave more offspring.’” While there are many types of biological predictions that can be made, “Probably nothing in biology is less predictable than the future course of evolution.”

It is worthwhile examining in some detail the four reasons that Mayr cites for the difficulty of biological prediction, because an important question that a Marxist would want to address is how a science of human history may have predictive power. It is one thing to explain something scientifically; it is another to be able to predict the future course of events. The first reason he gives is the “randomness of an event with respect to the significance of the event.” In particular, DNA mutations are random: “The occurrence of a given mutation is in no way related to the evolutionary needs of the particular organism or of the population to which it belongs.” Similarly with recombination. Second, “Uniqueness of all entities at the higher levels of biological integration.” Third, “extreme complexity.” And fourth, “Emergence of new qualities at higher levels of integration.”

I am not sure I see a problem with the latter three reasons. Mayr himself points out that the uniqueness of individuals still allows for statistical predictions, and draws an analogy to particles in a gas moving individually in different and unpredictable directions, but having predictable effects at a more macroscopic level. Moreover, extremely complex entities do not necessarily preclude predictability. Bring a fire to a man’s hand and he will withdraw it, regardless of how complex his biological constitution may be. One can predict the stages through which a man will pass in his biological development as well, because this extremely complex development is nevertheless regulated by genetic mechanisms. Finally, certainly with complex entities one sees the emergence of new characteristics, however one also sees the emergence of new laws, of new regularities, which allow predictions at the higher level of organization.

It seems to me that the first reason is the most significant. Evolution involves a large degree of randomness, and there is no direct relationship between the “evolutionary needs” of a population with this randomness. However, I am not convinced that this really eliminates the ability to make predictions about evolution either. Can one not predict that if one introduces a species of bird into an environment in which the only source of food favors birds with larger beaks, that the population of birds will evolve toward larger beaks? One knows that there is variation in beak size and this is governed by different allele frequencies. The larger beaks will tend to be selected for. Of course, the prediction is highly conditional—assuming that the birds do not find a different source of food; assuming that a mutation is not introduced that sends the population in a different evolutionary direction; etc. Nevertheless, randomness in mutation and recombination does not do away entirely with the ability to make predictions.

How to bring this discussion to the question of historical laws and historical predictions? While I have argued that predictions about biological evolution are still possible, I think the case can be made more strongly for social development, which involves very different forms of organization than biological evolution. Human societies are highly regulated in a way that biological populations in general are not, and this introduced very definite “evolutionary pressures” and much more predictable responses to these pressures. In particular, the process of production and the growth of the productive forces replaces evolution as the main driving force of the development of the human species [though of course biological evolution has not disappeared].

As Marx wrote, “In the social production of their existence, men inevitable enter into definite relations, which are independent of their will, namely relations of production appropriate to a given stage in the development of their material forces of production…The mode of production of material life conditions the general process of social, political and intellectual life…At a certain stage of development, the material productive forces of society come into conflict with the existing relations of production,” which begins an era of social revolution. “In studying such transformations it is always necessary to distinguish between the material transformation of the economic conditions of production, which can be determined with the precision of natural science, and the legal, political, religious, artistic or philosophic—in short, ideological forms in which men become conscious of this conflict and fight it out.”

There is no real correlate to class structure at a biological level. One sees for the first time in the history of life on earth the emergence of a dynamic social structure that, through culture (by which I mean the use of tools and knowledge and language that is transmitted from generation to generation outside of the framework of the genome), comes to dominate historical change within the population. The social requirements for the continued development of the productive forces and human society are much more definite than the evolutionary requirements for the continued development of populations in general. This is because the development of the productive forces imposes definite constraints on the social relations that will allow for their further development. For example, the socialization of the production under capitalism can only be continued and developed through the abolition of the private ownership of the productive forces. The internationalization of the productive forces can only be further developed through the abolition of the system of competing nation-states. In this sense one can predict the necessary stages in the development of human society, the “material transformation of the economic conditions of production…can be determined with the precision of natural science.” [In the comments section of this post, I elaborate on the issues raised in this paragraph. I have also changed above the phrase "socialization of the productive forces" to "socialization of production."]

I would also make the argument that the “selection pressures” imposed by the requirements of the productive forces produce the required “mutations”, or individual actions and persons, with far greater regularity than evolutionary requirements produce the needed mutations in DNA. The required personalities and political tendencies are more or less direct products of the social environment, though “more or less” here encompasses a great deal, since the relationship between the material base of human society and ideological manifestations is a complex one. However, this relationship allows for a sort of Lamarkian, or non-genetic evolution of human society, thereby reducing the amount of randomness. In human history, and not in biological evolution, the need for birds with bigger beaks actually leads to the production of birds with bigger beaks.

This by no means diminishes the need for conscious action among men, for all changes in the social relations of production must be mediated through these conscious actions. The role of the subjective factor in the conflict between different social forces requires that any definite predictions be conditional upon decisions and actions made by individuals and by parties. One can predict with absolute certainty the emergence in the coming period of enormous social struggles on an international scale; one can say with certainty that the crisis of world capitalism and the further development of the productive forces can only be resolved through an international socialist movement. However, the result of these struggles and the success of this movement is an open question that remains to be decided.

On the Unity of the Genotype

In his book, Toward a New Philosophy of Biology, Ernst Mayr has an essay entitled “The Unity of the Genotype” that is well worth examining. He summarizes the views of a theoretical lineage (beginning with the Soviet philosopher Chetverikov in 1926) through Mayr himself as follows: “Free variability is found only in a limited portion of the genotype. Most genes are tied together into balanced complexes that resist change. The fitness of genes tied up in these complexes is determined far more by the fitness of the complex as a whole than by any functional qualities of the individual genes.” This view must be counterpoised with the Mendelian conception, which it seems to me finds its most modern expression in the writings of Richard Dawkins, of the independence, the segregation, of genes. Here the gene (however this may be defined, a tricky matter) is treated as an isolated unit, the ultimate unit of selection. Evolution is understood as the changing of gene frequencies in a population.

In contrast, Mayr argues that it is necessary to treat the entire genotype as a unified complex of interacting parts. He traces this back to Darwin’s concept of correlation of growth, formulated in the Origin of Species, as the observation “that the whole organization is so tied together during its growth and development, that when slight variations in any part occur, and are accumulated through natural selection, other parts become modified.” Mayr brings in several different manifestations of the cohesion of the genotype, including Lerner’s concept of genetic homeostasis, the tendency for a population to loose some or most of an artificially selected trait when the selection pressure is removed; and the often-observed narrowness of hybrid zones, in which gene flow between two species that have come into contact with each other does not extend beyond a narrow band surrounding the area of cross-mating.

He draws the following conclusions from these observations: “(1) Since the fitness of a gene depends in part on the success of its interaction with its genetic background, it is no longer possible to assign an absolute selective value to a gene. A gene has potentially as many selective values as it has possible genetic backgrounds; (2) The target of selection does not consist of single genes but rather of such components of the phenotype as the eye, the legs, the flower, the thermo-regulatory or photo-synthetic apparatus, etc. …”

The concept of the cohesion of the genotype is useful, because it helps us comprehend certain features of the biological world that would otherwise be difficult to explain. There are, for example, only a certain limited number of animal “types,” the Bauplane: invertebrates, vertebrates, insects, arachnids, etc., and species within each type share a remarkable degree of similarity (the finger bones in a bat wing and in the hand of a human, e.g.). Why is evolution so conservative? Mayr suggests that one possible explanation is that a major change in the underlying structure of an organism (for example, the addition of a new set of extremities) is usually so disruptive to the expression of the genotype as a whole that it is strongly selected against. “The same phenomenon is illustrated by the gill arches that still dominate the ontogeny of land-living vertebrates,” he notes. “It is obvious in all these cases that development is controlled by such a large number of interacting genes that the selection pressure to eliminate vestigial structures is less effective than the selection to maintain the efficiency of well established development pathways.”

The concept also helps explain the evidence of highly uneven rates of evolution (periods of relative stasis or gradual change followed by relatively rapid change). The unity of the genotype acts as a stabilizing force, resisting major evolutionary change, however this stability can be disrupted in certain situations such as the breakaway of “founder populations” (small populations that are separated from the population as a whole), which are confronted with new environmental conditions. [Mayr was really the first theorist to develop this concept, which he called “genetic revolutions,” though it has since become eclipsed by Gould and Eldridge’s more dubious theory of punctuated equilibria, which it is sometimes argued is in conflict with Darwin’s theory of natural selection].

For the moment I am simply throwing this concept out there, but hopefully I will develop these ideas in future posts. I think that it is highly significant that the lineage emerged first among Soviet scientists in the 1920s, pre-Lysenko and prior to the major phases of Stalinist repression. A serious examination of the work of these geneticists would be well worth the effort.