"VITAL ARTICLES ON SCIENCE/CREATION"
No. 166 MUTATION FIXATION:
A DEAD END FOR MACRO-EVOLUTION
E. Calvin Beisner, M.A.
Most arguments against the possibility of mutation as a mechanism for
evolution revolve around two premises: that mutations are almost always
harmful, and that the idea of their improving rather than harming or-
ganisms is contrary to the Second Law of Thermodynamics, which tells
us that matter and energy naturally tend toward greater randomness
rather than greater order and complexity. These are two sides of the
same coin, actually, the latter arguing from principle and the former from
Rarely, though, do arguments against mutation as the mechanism for
evolution consider at once the many conditions that must be met if
mutation is to bring about macro-evolutionary change (that is, change
from one basic kind of life to another). Yet examining the probabilities of
these conditions all being met together provides excellent evidence
against evolution and in favor of creation.
Fortunately, geneticist R.H. Byles has made the job easy for us by
discussing nine important conditions in an article on the subject.'
1. Neutral Enuironment
Byless first condition is: "Natural selection must be inconsequential
at the locus or loci under investigation." This is because natural selec-
tion tends to work against fixation of mutations-in other words, it tends
to prevent their becoming a permanent part of the gene pool of a popu-
lation. Natural selection keeps things stable rather than helping them to
change. B. Clarke points out that even so-called advantageous mutations
are harmful in that, because of increased competition, they can reduce
population size, making their fixation nearly impossible. He adds that
they will almost certainly lead to extinction of the mutant gene or
organism, and possibly even the entire population.2
The effect of Byles's first condition is that the environment must be
selectively neutral, or else the mutant gene will never be retained in the
population, preventing even slight change. But according to J.T. Giesel,
most locations are almost certainly not selectively neutral.3 Thus, in the
vast majority of cases, Byles's first condition will not be met.
No Structural Change
Byles's second condition is: "There must be no pleiotropic effect
involved math the locus or loci or, if such effect exists, all the phenotypic
structures involved must be selectively neutral." This means that there
either must be no changes in physical structure involved, or they must
be selectively neutral. If none are involved, then of course evolution does
not occur. But if only those occur that are selectively neutral, then they
are of no advantage to the mutant and survival of the fittest does not
affect it or its non-mutant relatives; again, no evolution.
Not only would mutations that met this condition appear to contribute
little or nothing to evolution, but also they would appear never to happen
-or nearly never, anyway. G. Ledyard Stebbins tells us that within the
gene there is no such thing as an inactive site at which a mutation will
not affect the adaptive properties of the gene.' "Every character of an
organism is affected by all genes," writes Ernst Mayr, "and every gene
affects all characters. It is this interaction that accounts for the closely
knit functional integration of the genotype as a whole."5
In other words, there may well be no such thing as a mutation having
no structural change in the organism. Yet Byles says that a requirement
for the fixation of a mutation is that it have none, or that the effect it has
must be selectively neutral. Neither case appears ever to happen, and
even if the latter did, it would not lead to macro-evolution since it would
leave the mutant no more "fit" than any of its relatives. Indeed it would
probably be less "fit" because of the tendency of natural selection to
weed out rather than preserve mutations in a gene pool.
Net Effect Must be Unidirectional
Byles's third condition is: ". . the mutational event must be recurrent
and, forthermore, the rate of back mutation must be so small as to be
irrelevant." Byles himself admits, though, that even recurrent mutations
are almost never retained in the population: ". . non-recurrent mutations
have a very low probability of remaining in the gene pool at all ... the
odds against a recurrent mutation being retained in the gene pool for any
significant number of generations are very high." And even "most re-
current mutations have been observed to retain the potential for back
mutation." It seems that neither part of his third condition MAII be fulfilled;
yet Byles makes it clear in his article that all the conditions must be
fulfilled in order for mutations to be fixed in a population.
High Mutation Rate
Byles's fourth condition is: "The mutation rate at the relevant locus or
loci must be very large." Yet Francisco Ayala says, "It is probably fair to
estimate the frequency of a majority of mutations in higher organisms
between one in ten thousand and one in a million per gene per generation."6
Byles himself comments on Lerner's estimate of one hundred mutations
per one million gametes (one in ten thousand). "Obviously, a mutation
rate this small, even given a complete absence of back mutation (which
appears never to occur), would result in a very small change in a given
gene pool, even given large numbers of generations. This has long been
considered one of the major stumbling blocks to the [Probable Mutation
Effect]. . . In order for the P.M.E. to be effective, very high mutation
rates are clearly necessary."
So it appears that this condition, too, is likely never met in nature.
Byless fifth condition is that the population involved must be large.
He stipulates this because small populations can easily be destroyed by
a mutation. And, as population size decreases, the probability that a
mutation will be eliminated increases.
Dobzhansky, Hecht, and Steers, however, postulate that a small
population vath much inbreeding is important: ". . the ideal conditions
for rapid evolution ... are provided by a species which is divided into a
number of small local sub-populations that are nearly but not completely
isolated and small enough so that a moderate degree of inbreeding takes
place. . . The division of a species into two or more subspecies is of
course dependent on complete isolation being achieved in some way."7
It seems that evolutionists themselves have realized a great problem
but are unable to deal with it. In a small population, a mutation will
almost certainly be eliminated. Yet a small population is needed for evo-
lution to occur. Here indeed is an impasse. But the problem gets worse.
Byles adds (in contradiction of Dobzhansky, Hecht, and Steere), "If
the investigator is dealing with a population which is undergoing contact
with genetically dissimilar neighbors, the effect of the mutation is inevi-
tably so minor as to be indetectable. Therefore, to argue that mutation
is the cause of change in the population's genetic structure, one must
also of necessity argue that this population is not undergoing a process
of hybridization." In other words, if the population is large, the effect of
the mutation is almost nil. Even when Byles's condition is met, then, the
effects of the mutations are almost zero on the entire population. And,
furthermore, while Dobzhansky, Hecht, and Steere say some interbreed-
ing between dissimilar populations is necessary, Byles says it is death
to evolutionary change.
Selective Neutrality of Polygenes
Byles's sixth condition is: "Polygenes are not relevant to this argu-
ment, unless the entire anatomical complex is itself selectively neutral."
This means that for organisms of many genes, the mutation cannot be
fixed unless the whole anatomical structure of the organism is selectively
neutral relative to the gene which mutates. That this does not occur was
shown in our discussion of the second condition.
Byles's seventh condition is: "There must be little or no hybridizing
admixture." This of course is to avoid making the mutation itself insig-
nificant. But if the effect is actually significant, then this contradicts his
second condition, which was that the mutation must cause no significant
structural change (see under point 2 above). Furthermore, the only way
in which to have no hybridizing admixture is to have a small population
that is isolated from others of the same kind. This contradicts his fifth
condition. If the population is small, the probability of a mutant gene's
being eliminated rises steeply.
This seventh condition, if fulfilled, makes evolution impossible because
the mutation would not be retained due to the necessarily small popu-
lation. But if unfulfilled, it leaves evolution impossible due to the insig-
nificance of the effect of the mutation.
Necessity of High Penetrance
Byless eighth condition is: "The genetic structures involved must
have high 'penetrance.' " Put simply, this means that the genes must be
highly susceptible to mutation. It thus means almost the same as
Yet it occasions another problem. As soon as the structure becomes
highly susceptible to mutation, it must also become highly susceptible to
back mutation. But his third condition states that the rate of back muta-
tion must be irrelevant, Again there is contradiction: fulfill Condition
Eight and you can't fulfill Condition Three. Fulfill Condition Three and you
can't fulfill Condition Eight. Yet Byles says that all of the conditions must
be fulfilled for mutation fixaton to occur; and without mutation fixation
there is no macro-evolution.
Byles's ninth condition is: "The phenotype must have high heritability."
This condition is almost never met for mutational phenotypes. Byles
himself told us that the probability of retaining even a recurring mutation
is "very low."
It appears that the probability of meeting any one of these conditions
in nature is extremely low, if not non-existent. Recall now that the fifth
and seventh conditions effectively cancel each other out, as do the third
and eighth, and we are forced to the conclusion that it is impossible to
meet all the conditions. Mutation cannot be the mechanism for macro-
1. R.H. Byles, "Limiting Conditions for the Operation of the Probable Mutation Effece'Social
Biolo_qy, 19 (March, 1972):29-34. All citations from Byles in this article are from this source.
2. B. Clarke, "Mutation and Population Size," Heredity, 31 (Dec., 1973):367-79.
3. J.T. Giesel, "Maintenance of Genetic Variability in Natural Populations; Alternative Implica-
tions of the Charlesworth-Giesel Hypothesis," American naturalist, 106 (May, 1972):
412-14, p. 412.
4. G. Ledyard Stebbins, "Building Bridges Between Evolutionary Disciplines" Taxon 23(1)
(Feb., 1974):11-20, p. 14.
5. Ernst Mayr, Populations, Species and Evolution (Cambridge, Mass.: Harvard University
Press, 1970), p. 103.
6. Francisco J. Ayala, "Teleological Explanations in Evolutionary Biology," Philosophy of
Science, 37 (March, 1970), p. 3. Cited in Henry M. Morris, ed., Scientific Creationism
(San Diego, Calif.: Creation-Life, 1974), p. 55.
7. Theodosius Dobzhansky, et OI., Euolutionar_v Biolo_qy, Vol. 2 (N.Y.: Appleton-Century-
Croft, 1968), p. 259.