I strongly recommend you (and anyone else) read this little essay:
http://www.talkorigins.org/faqs/modern-synthesis.html
here's a pertinent excerpt:
It is important to note that Darwin's book "The Origin of Species by
Means of
Natural Selection" did two things. It summarized all of the evidence in
favor
of the idea that all organisms have descended with modification from a
common ancestor, and thus built a strong case for evolution. In addition
Darwin advocated natural selection as a mechanism of evolution.
Biologists no
longer question whether evolution has occurred or is occurring. That part of
Darwin's book is now considered to be so overwhelmingly demonstrated that
is is often referred to as the FACT of evolution. However, the MECHANISM of
evolution is still debated.
We have learned much since Darwin's time and it is no longer appropriate to
claim that evolutionary biologists believe that Darwin's theory of Natural
Selection is the best theory of the mechanism of evolution. I can understand
why this point may not be appreciated by the average non-scientist because
natural selection is easy to understand at a superficial level. It has been
widely promoted in the popular press and the image of "survival of the
fittest" is too powerful and too convenient.
During the first part of this century the incorporation of genetics and
population biology into studies of evolution led to a Neo-Darwinian
theory of
evolution that recognized the importance of mutation and variation within a
population. Natural selection then became a process that altered the
frequency of genes in a population and this defined evolution. This point of
view held sway for many decades but more recently the classic
Neo-Darwinian view has been replaced by a new concept which includes
several other mechanisms in addition to natural selection. Current ideas on
evolution are usually referred to as the Modern Synthesis which is described
by Futuyma;
"The major tenets of the evolutionary synthesis, then, were that
populations contain genetic variation that arises by random (ie.
not adaptively directed) mutation and recombination; that
populations evolve by changes in gene frequency brought about
by random genetic drift, gene flow, and especially natural
selection; that most adaptive genetic variants have individually
slight phenotypic effects so that phenotypic changes are gradual
(although some alleles with discrete effects may be advantageous,
as in certain color polymorphisms); that diversification comes
about by speciation, which normally entails the gradual evolution
of reproductive isolation among populations; and that these
processes, continued for sufficiently long, give rise to changes of
such great magnitude as to warrant the designation of higher
taxonomic levels (genera, families, and so forth)."
- Futuyma, D.J. in Evolutionary Biology, Sinauer Associates,
1986; p.12
This description would be incomprehensible to Darwin since he was unaware
of genes and genetic drift. The modern theory of the mechanism of evolution
differs from Darwinism in three important respects:
1.It recognizes several mechanisms of evolution in addition to natural
selection. One of these, random genetic drift, may be as important as
natural selection.
2.It recognizes that characteristics are inherited as discrete
entities called
genes. Variation within a population is due to the presence of
multiple
alleles of a gene.
3.It postulates that speciation is (usually) due to the gradual
accumulation of small genetic changes. This is equivalent to
saying that
macroevolution is simply a lot of microevolution.
In other words, the Modern Synthesis is a theory about how evolution works
at the level of genes, phenotypes, and populations whereas Darwinism was
concerned mainly with organisms, speciation and individuals. This is a major
paradigm shift and those who fail to appreciate it find themselves out
of step
with the thinking of evolutionary biologists. Many instances of such
confusion
can be seen here in the newsgroups, in the popular press, and in the
writings of anti-evolutionists.
Susan
----------
For if there is a sin against life, it consists not so much in despairing
of life as in hoping for another and in eluding the implacable grandeur of
this one.
--Albert Camus
http://www.telepath.com/susanb/
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