Natural Selection

By Richard C. Lewontin
The New York Review of Books, May 27, 2010


Edited by Andy Ross

   What Darwin Got Wrong
   By Jerry Fodor and Massimo Piattelli-Palmarini
   Farrar, Straus and Giroux, 264 pages

A modern formulation of evolution by natural selection consists of three principles:

1. The principle of variation: among individuals in a population there is variation in form, physiology, and behavior.

2. The principle of heredity: offspring resemble their parents more than they resemble unrelated individuals.

3. The principle of differential reproduction: in a given environment, some forms are more likely to survive and produce more offspring than other forms.

To explain continued evolution of new forms we must also add a fourth principle:

4. The principle of mutation: new heritable variation is constantly occurring.

This outline does not explain the actual forms of life that have evolved. An immense amount of biology is missing.

Fodor and Piattelli-Palmarini say that Darwin's theory of selection is empty. They discuss a number of complexities at the molecular, cellular, developmental, and physiological level that need to be taken into account as well.

First, the proteins that result from the processing of genetic information may enter into multiple metabolic and developmental pathways. The interaction is not universal, or the organism would be so inflexible as to make life impossible. The intensity of interaction between parts is also strongly dependent on the circumstances of life.

Second, there are molecular interdependencies that arise from the fact that genes are organized onto chromosomes. The translation of a gene in the process of producing a protein is sensitive to changes in DNA that is nearby on the chromosome strand. So several genes of quite different specificity can be affected by the same change in the chromosome.

Third, the organization of genes onto the chromosomes in the cell means that when an offspring has inherited a particular form of one gene from a parent, it will probably also inherit the forms of a number of other genes that lie nearby on the same chromosome strand. Selection on one function may result in inherited changes in other functions.

In natural selection it is not traits that are selected but organisms. The traits they possess will determine their contribution to the next generation. Organisms are selected as a consequence of their total biology.

Every living creature must be in some sort of adaptive correspondence to its conditions of life or else it would be dead. But the "adaptation of organisms to their environment" is a characterization that misses half the story. It is based on the metaphor of the "ecological niche," a preexistent way of making a living into which organisms must fit or die. But there is an infinity of ways that organisms might make a living.

Every kind of organism reforms the world around itself and creates its own ecological niche that is in constant flux as the organism behaves and metabolizes. Organisms do not fit into niches, they construct them.

Evolutionary theory is under attack by religious fundamentalists using the ambiguity of the word "theory" to suggest that evolution as a natural process is "only a theory." When two accomplished intellectuals make the statement "Darwin's theory of selection is empty," they generate an anger that makes it almost impossible for biologists to give serious consideration to their argument.

AR  Fodor's decision to put his name to a book with that title is a scandalous lapse for a serious philosopher. Darwin didn't get it wrong, he just didn't have the whole story.


By Richard C. Lewontin
The New York Review of Books, May 26, 2011

Edited by Andy Ross

The twentieth century was a period of immense popularity of genetic explanations for class and race differences in mental ability and temperament. But such theories have now virtually disappeared from public view, largely because biologists made an effort to explain their errors.

Now genetic theories for the causation of physical disorders have become the mode. The announcement in 2001 that the human genome had been sequenced was taken to herald a new era, in which all diseases would be treated and cured by the replacement of faulty DNA. But the search for genes underlying common causes of mortality have so far yielded virtually nothing useful.

Genetics has been a subtractive science. It is based on the analysis of the difference between natural or wild-type organisms and those with some genetic defect that may interfere in some observable way with regular function. The comparison requires that the organisms being studied are identical in all other respects, and that the environment does not generate atypical responses yet allows the possible effect of the genetic perturbation to be observed. Such an approach might never reveal how nature and nurture normally interact.

Synthetic biologists construct living systems from their molecular elements. Some 99 percent of the DNA in an organism is not part of its genes in the usual sense. It does not code for a sequence of amino acids that will make long chains that will fold up to form proteins. This nongenic DNA, which used to be called junk DNA, seems to regulate how often, when, and in which cells the DNA of genes is read in order to make the chains and to specify how they will fold.