Find No Genetic Evidence For Evolution
of Darwin's theory of evolution point to flaws in the fossil record
(no new species, no missing links) as evidence that the theory is
false. But in the 1960s scientists discovered genetic material
called DNA and were quick to suggest that the rate of change in
DNA is evidence that confirms Darwin's theory of evolution.
it is convenient for evolutionary biologists to assume that various
DNA proteins evolve at a fixed rate, a recent study blows a hole
in this theory. The September 25 issue of the Proceedings
of the National Academy of Sciences, geneticist Francisco Rodriguez-Trelles
and colleagues at the University of California, Irvine, indicate
the idea of a molecular clock may be hopelessly flawed. "It
may be ripe for the pawnshop" say Menno Schilthuizen, writing
in Science Now.
the different mutation rates for three well-known genes for 78 species,
researchers found widely different mutation rates even for closely
related species. "Molecular clocks are much more erratic
than previously thought and practically useless to keep accurate
evolutionary time," says Schilthuizen. The authors of
the research conclude that the neutral theory of molecular evolution
(predictable or constant rates of change) is flawed and that changes
in the rate of variation are left to the vagaries of natural selection
(randomness). With no evidence to confirm the neutral theory
of molecular evolution, scientists say this amounts to a "denial
of there being a molecular clock."
- - - - Guanine Cytosine Adenine Thymine
- - - - Sugar
A DNA Nucleotide Sequence
Positions of the middle four proteins differs
is made up of many subunits or strings of sequenced proteins strung
between a sugar and a phosphate molecule (called a nucleotide).
Think of a wash line in the back yard. There are
two poles (the sugar and phosphate molecules) with four proteins
(amino acids guanine, cytosine, adenine, thymine) hanging
on the wash line. There are many of these "wash lines" in
one gene and over time some of the proteins hanging on the wash
line change their positions. One protein may be substituted
for another, which is called a mutation. Different species of life
have some of the same genes and therefore the rate of change (number
of protein substitutions) can be used to calibrate a DNA clock.
Comparative studies of different proteins in various groups
of organisms tend to show that the average number of amino-acid
substitutions per site per year is typically around 10-9.
Calculating backwards, scientists have attempted to use the
DNA clock to determine when, let's say, chimpanzees and man diverged
from the same genetic tree. There are a lot of assumptions here
(even that there is a genetic tree at all) but the scientists believe
humans and chimps split off from a common ancestor about 5.5 million
the DNA clock is not so reliable. Paleontologists calculate
the Cambrian explosion, the sudden appearance of a fossil record
that is rich in almost every species of life, occurred about 540
million years ago. But DNA clock estimations come up with
a date of 1 billion years ago for the Cambrian explosion. So
there is an unexplainable 500-million year gap. Which provides
the most accurate dating, the fossils or the genes?
so-called neutral theory of evolution holds that DNA mutations (protein
substitutions) accumulate at an approximately constant rate as long
as the DNA retains its original functions. The differences between
the sequences of the same DNA segment (or protein) in two species
of life would then be proportional to the time the species diverged
from a common ancestor. The undeniable problem is, different DNA
protein sequences (or even different parts of the same gene) "evolve"
or change at markedly different rates. For example, mutation rates
in primates are slower than in rodents. This also assumes that all
mutations move progressively rather than in reverse.
what these researchers say is true, that the theory of a molecular
clock is hopelessly flawed, scientists have some real reorganization
on their hands. There are no less than 30 textbooks written
on molecular evolution in the past decade and numerous PhDs awarded
in this area of investigation. To date, no convincing evidence
for a phylogeny tree has ever been produced. The evolutionary
trees shown in biology textbooks are simply theory, not science.
Genetics does not confirm its existence either, though it
took scientists more than three decades to determine this. Few
scientists are expected to abandon the theory of neutral molecular
evolution anytime soon.
Rodriguez-Trelles, Rosa Tarrio, Francisco J. Ayala, Proceedings
National Academy of Sciences USA, Volume 98, pages 11405-10,
September 25, 2001
M, Molecular Clock Not Exactly Swiss, Science Now, Sept.
of Biology, Oxford University Press, Market House Books,
Human Genome Research Institute
Sardi is a journalist residing in Diamond Bar, California. His new
God vs. Big Science
(Here & Now Books, 107 pages, illustrated, $7.00) at
© 2001 by the Word of Knowledge Agency, San Dimas, California.