MENTAL FURNITURE #8
Darwinian Evolution
©1997 Dennis Leri
In his introduction to Darwin's The Expression of Emotions in Man and Animals Konrad Lorenz has this to say: "...Jacob von Uexkull once said rather pessimistically that today's truth was, after all, nothing but the error of tomorrow. Thereupon... Otto Koehler answered, 'No the truth of today is the special case of tomorrow!'... This second statement contains a very much deeper truth. In science, and particularly in biology, the discoverer of a new explanatory principle is more than apt to overrate the range of its applicability. ...One may indulgently regard this little weakness as the well-merited prerogative of genius, because the great man's pupils, though lesser discovers, are apt to be better at verification than their inspired teacher and can be relied upon to clip the wings of his genius when it threatens to soar too high. It is only when the pupils degenerate into disciples who unquestioningly accept the far sweeping statements of their master that danger arises, and a newly born epistemophagus (knowledge-devouring) monster, another 'ism' rears its ugly head."
"However, the greatest of all discoverers in the field of biology did not commit the error just discussed: when Charles Darwin discovered natural selection, the explanatory principle that was destined to change our outlook on man and the world more than any other before it, he decidedly did not overestimate the number of phenomena that could be explained on its basis. If anything, he erred on the side of understatement.... Like all really great scientific discoverers, Darwin possessed an almost uncanny ability to reason on the basis of hypotheses which were not only provisional and vague but subconscious. He deduced correct consequences from facts more suspected than known, and verified both the theory and the facts by the obvious truth of the conclusions thus reached. In other words, a man like Darwin knows more than he thinks he knows, and it is not surprising that the consequences of his knowledge reach far and in different directions."
"Behavior patterns are just as conservatively and reliably characters of the species as are the forms of bones, teeth, or any other bodily structures. Similarities in inherited behavior unite the members of a species, of a genus, and of even the largest taxonomic units in exactly the same way in which bodily characters do so. The conservative persistence of behavior patterns, even after they have outlived, in the evolution of a species, their original function is exactly the same as that of organs... The adaptation of the behavior patterns of and organism to its environment is achieved in exactly the same manner as that of its organs, that is to say on the basis of information which the species has gained in the course of its evolution by the age-old method of mutation and selection. This is true not only for the relatively rigid patterns of form or behavior, but also for the complicated mechanisms of adaptive modification, among which are those generally assumed under the concept of learning."
One of the underpinnings of Moshe's concept of learning how to learn is the notion of organic learning. Essential to organic learning is the theory of evolution. Not just any old evolutionary theory but Darwin's. Evolution as conceived of by Darwin is one of the most powerful theories in the history of science and Western thought. It is also one of the most misunderstood theories. Take the phrase "survival of the fittest." Some suppose that it summarizes evolutionary theory. It does not. The phrase is both incomplete and misleading. The idea that evolution is progressive, that present life forms are improvements over earlier forms, is also a misinterpretation. Another common error in characterizing evolutionary theory is that organisms can be arranged on an evolutionary ladder from bacteria to man.
The more orthodox definition of evolution is as a change in the gene pool of a population over time. The gene pool is the set of all genes in a species or population. The English moth, Biston betularia, is a frequently cited example of observed evolution. In 19th century industrial England, rare black variants spread through this moth population as a result of their habitat becoming darkened by soot from factories. Birds could see the lighter colored moths more readily and ate more of them. The moth population changed from mostly light colored moths to mostly dark colored moths. Since their color was determined by a single gene, the change in frequency of dark colored moths represented a change in the gene pool. This change was, by definition, evolution.
Evolution is often characterized as either 'microevolution' as with the moths above or "macroevolution" when referring to larger changes (such as the emergence of a new species) taking place over longer periods of time. Macroevolution is cumulative microevolution. In defining evolution as a change in the gene pool it means that evolution is a population level phenomena. Therefore, only groups of organisms evolve. Individual organisms do not evolve. Evolutionarily stated, it is necessary to view populations as collections of individuals with different traits. For example, as the frequency of black moths increased, the "average" moth did not get progressively darker. There were never any "average" half-white/half-black moths in the population.
Evolution is often equated with morphological change, i.e. organisms changing shape and/or size over time. An example would be a dinosaur species evolving into a species of bird. It is important to note that evolution is often accompanied by morphological change, but this need not be the case. Evolution can occur without morphological change; and morphological change can occur without evolution. That humans are larger now than in the past is not an example of evolutionary change. Better diet and medicine brought about this change. The gene pool did not change -- only its manifestation did.
An organism's phenotype -- comprised by its morphological, physiological, biochemical, behavioral and other properties -- is determined by its genes and its environment. Phenotypic changes induced solely by changes in environment do not count as evolution because they are not heritable; in other words, the change is not passed on to the organism's offspring. The fundamental error of Lamarckian evolution was to assume that learned characteristics could be passed on. Most changes due to environment are fairly subtle (e.g. size differences). Large scale phenotypic changes (such as dinosaur to bird) are obviously due to genetic changes, and therefore are evolution.
Evolution is not progress. Organisms simply adapt to their current surroundings and do not necessarily become "better" over time. Gregory Bateson called it survival of "the fit" rather than of "the fittest." A trait or strategy that is successful at one time may be deleterious at another. Studies in yeast have shown that "more evolved" strains of yeast can be competitively inferior to "less evolved" strains. An organism's success depends a great deal on the behavior of its contemporaries; for most traits or behaviors there is likely no optimal design or strategy, only contingent ones. Bio-epistemologist Francisco Varela prefers the notion 'viable' to that of 'optimal' when specifying the ongoing fit of organism to environment and environment to organism.
How does evolution work? If evolution is a change in the gene pool; what causes the gene pool to change? Several mechanisms can change a gene pool, among them: natural selection, genetic drift, gene flow, mutation and recombination. It is important to understand the difference between evolution and the mechanisms that bring about this change. Why? Because while the fact of evolution is not in question, the processes bringing it about are not all clearly understood. Bringing about a change in the gene pool assumes that there is genetic variation in the population to begin with, or a way to generate it. Genetic variation is "grist for the evolutionary mill." For example, if there were no dark moths, the population could not have evolved from mostly light to mostly dark. In order for continuing evolution there must be mechanisms to increase or create genetic variation (e.g. mutation) and mechanisms to decrease it (e.g. natural selection and genetic drift).
Natural selection is the only mechanism of adaptive evolution; it is defined as differential reproductive success of pre-existing classes of genetic variants in the gene pool. In other words, the genetic constitution of some individuals are (on average) better than others at contributing their genetic variations to the next generation's gene pool. Selection is not a force in the sense that gravity or magnetism is no matter how often some biologists speak of it that way. Selection is not a guided or cognizant entity; it is simply an effect. Darwin stated the case originally that it was 'as if there were a natural selection, comparable in its separating effect to the artificial selection a farmer makes of the varieties that interest him. Darwin himself was quite clear in his metaphoric use of the term selection. There is in the theory of evolution no need for the environment to play the role of 'selector.' When supplied with genetic variation, natural selection allows organisms to adapt to their current environment and their environments to them. It does not, however, have any foresight. Structures or behaviors do not evolve for future utility. An organism must be, to some degree, adapted to its environment at each stage of its evolution. As the environment changes, new traits (new combinations of genetic variation) may be selected for. As an organism changes it modifies its environment. Large changes in populations are the result of cumulative natural selection -- numerous small changes are introduced into the population by mutation; the small minority of these changes that result in a greater reproductive output of their bearers are amplified in frequency by selection.
Natural selection works at the level of the individual. In the example I gave earlier, dark colored moths had higher reproductive success because light colored moths suffered a higher predation rate. The decline of light colored genetic variants was caused by light colored individuals being removed from the gene pool (selected against). It is the individual organism that either reproduces or fails to reproduce. Genes are not the unit of selection (because their success depends on the organism's other genes as well); neither are groups of organisms a unit of selection. There are some exceptions to this 'rule.' The individual organism reproduces or fails to reproduce. It competes primarily with others of it own species for its reproductive success. Natural selection does not necessarily produce individually optimal structures or behaviors. Selection targets the organism as a whole, not individual traits. So, specific traits are not optimized, but rather combinations of traits. In addition, natural selection may not necessarily even select for the most optimal set of traits.
Other important mechanisms of evolution are genetic drift, mutation, recombination and gene flow. They are worth looking into. The main thing to remember is that evolution is not progress. Evolution should not be represented as a series of improvements from simple cells, through more complex life forms, to humans (the pinnacle of evolution). Modern biologists hold that all species have descended from a common ancestor. As time went on, different lineages of organisms were modified with descent to adapt to their environments. Thus, evolution is best viewed as a branching tree or bush, with the tips of each branch representing currently living species. No living organisms today are our ancestors. Every living species is as fully modern as we are with its own unique evolutionary history. No extant species are "lower life forms," atavistic stepping stones paving the road to humanity. A related, and common, fallacy about evolution is that humans evolved from living species of apes. This is not the case -- humans and apes share a common ancestor. Both humans and living apes are fully modern species; the ancestor we evolved from is now extinct and was not the same as present day apes (or humans for that matter). Our closest relatives are the chimpanzee and the pygmy chimp. Evolution is still occurring through the mechanisms listed above; all organisms and their surroundings are co-evolving.
The theory of evolution is what unifies all of biology. Evolutionary biologists can provide an elegant answer to the question, "How did we human beings get here?" Evolutionary theory distinguishes and differentiates between an individual's personal history (ontogeny) and her or his impersonal species history (phylogeny). The difference between the ontogenetic and the phylogenetic is the difference that makes a difference in Feldenkrais' profound approach to learning. The very notion of 'function,' as used by Feldenkrais, binds together the biological means of organismic viability with new instances for a fuller realization of one's potential. We individuate in the time allotted to each of us against the backdrop of the broad expanse of evolutionary time. By utilizing the distinction between phylogenetic and ontogenetic patterns of behavior we can use the former to influence and change the latter. Borrowing from Lorenz's introduction we can say Moshe Feldenkrais did not overestimate the breadth of application of his ideas and, if anything, he erred on the side of understatement. Moshe knew more than he thought he knew, and it is not surprising that the consequences of his knowledge reach far and in different directions.
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