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.
