Genetics of the Evolutionary Process

A review of Genetics of the Evolutionary Process by Rob Mason

Theodosius Dobzhansky, was a Russian geneticist who moved to the United States and provided laboratory evidence for natural selection and variation where previously there had been only field observation. In his book: Genetics of the Evolutionary Process he begins chapter 1 by by stating that a man consists of seven octillion ( the number represented as one followed by 27 zeros) atoms grouped in about ten trillion cells, he then goes on to ask the question, how can an agglomeration of atoms experience a feeling of life, joy, suffering and discriminate between beauty and ugliness. He explains that two kinds of answers have been proposed.  Vitalists (a doctrine that attributes the viability of a living organism to a vital principle distinct from the physical and chemical processes of life) assume that living bodies are formed through the intervention of occult forces, variously called entelechy (the realization of potential), or directiveness and creativeness as being fundamental characterists inherent in life. Mechanists on the other hand define life as an emergent property of particular kinds of complex systems and believe life can be understood without recourse to the assumtion of any transcendental powers.

Dobzhansky explains that the theory of vitalism often, though not always, goes together with creationism, that is, with the belief that the world as a whole, and the living species in particular, were created just a few thousand years ago and have remained essentially unchanged since then.  Larmark, Darwin and others after them expounded a different view: the living world that we observe at present has been shaped during billions of years of evolutionary history. The organisms now living have evolved gradually from ancestors that were generally more and more different from their descendants as one looks progressively farther back in time.  Some vitalists do not deny evolution, but claim that it is guided towards predestined ends by inscrutable forces.  Darwin thought otherwise. He posited natural selection as a process that impels and directs changes. Subsequent research has on the whole vindicated his view.

Adaptedness/ Teleology

The structures and functions of living bodies are said to exhibit adaptedness, or end directedness when they are shown to contribute to individual survival or to reproduction, which makes possible the survival of the species.  Creationists believe that living bodies are engineered by a wise creator; according to this view, organisms, like human contrivances exhibit external teleology. To vitalists, teleology is an elemental property immanent in life.  It cannot and need not be analyzed any further.  To most biologists since Darwin, internal teleology is a product of evolutionary development.  The adaptedness is neither devised or planned by any external conscious agent; it is not guaranteed by providential ability of living matter to act purposefully.  Rather, it has evolved and is being maintained and often improved by natural selection. 

How Did Life Originate?

On page 7,  Dobzhansky speculates on how life originated. He says that it has been a biological certitude that life arises only from other life - omne vivum ex vivo - and that considerable research and speculation have been devoted to this question in recent years. Very briefly the following scheme is proposed.  Some chemical compounds were formed under the conditions of the primitive, lifeless earth that are now only obtained from living bodies. Experiments are therefore contrived to simulate the conditions supposed to have existed on the primitive earth.  Several amino acids and even peptides and nucleotides have been thus obtained.  Primordial oceans may, then, have contained a very dilute "broth" of organic compounds. But even if such a "broth" existed, the origin in it of the first self reproducing and hence living system remains an unsolved problem. Some writers have bravely, but not convincingly declared that, given the basic chemical properties of matter, the origin of life was inevitable.  Since life has in fact appeared, its origin was indeed "inevitable."  Yet the problem cannot be resolved by a fiat (formal authorization); nobody really knows just how great an order of improbability this "inevitable" event involved.  Hence we cannot be sure that, if there exist a million million planets more or less resembling the earth, any of them had extra-terrestrial life originate and evolve.

The Raw Materials of the Evolutionary Process

Dobzhansky explains how random mutations are the raw materials of the evolutionary process.  Natural selection orders them in functionally coherent adaptive systems.  Mutations are often descibed as accidental, random, undirected chance events. Just what does this mean? Mutations are accidents, because the transmission of hereditary information normally involves precise copying. A mutant gene is, then, an imperfect copy of the ancestral gene.  Mutations are undirected with respect to the adaptive needs of the species. They arise regardless of their actual or potential usefulness.  It may seem an imperfection of nature that mutability is not restricted to changes that enhance the adaptedness of their carriers. However, only a vitalist Pangloss (Candide) could imagine that the genes know how and when it is good for them to mutate.

Survival of the fittest in the struggle for life

Darwin accepted Herbert Spencer's slogan "survival of the fittest in the struggle for life" as an alternative description for natural selection.  At present this term seems inappropriate. Not only the fittest but also the tolerably fit survive and reproduce. Under flexible or soft selection all the carriers of the same array of genotypes may survive when the population is increasing in size, and may be iliminated when it is shrinking.