concept stressed by the proponents of punctuated equilibrium
theory is that of "restricted populations." By this, they
mean that the emergence of new species comes about in communities
containing very small numbers of plants or animals. According
to this claim, large populations of animals show no evolutionary
development and maintain their "stasis." But small groups
sometimes become separated from these communities, and these
"isolated" groups mate only amongst themselves. (It is hypothesized
that this usually stems from geographical conditions.) Macromutations
are supposed to be most effective within such small, inbreeding
groups, and that is how rapid "speciation" can take place.
But why do proponents of the punctuated equilibrium
theory insist so much on the concept of restricted populations?
The reason is clear: Their aim is provide an explanation for
the absence of intermediate forms in the fossil record.
However, scientific experiments
and observations carried out in recent years have revealed
that being in a restricted population is not an advantage
from the genetic point of view, but rather a disadvantage.
Far from developing in such a way as to give rise to new species,
small populations give rise to serious genetic defects. The
reason for this is that in restricted populations individuals
must continually mate within a narrow genetic pool. For this
reason, normally heterozygous individuals become increasingly
homozygous. This means that defective genes which are normally
recessive become dominant, with the result that genetic defects
and sickness increase within the population.178
In order to examine this matter,
a 35-year study of a small, inbred population of chickens
was carried out. It was found that the individual chickens
became progressively weaker from the genetic point of view
over time. Their egg production fell from 100 to 80 percent
of individuals, and their fertility declined from 93 to 74
percent. But when chickens from other regions were added to
the population, this trend toward genetic weakening was halted
and even reversed. With the infusion of new genes from outside
the restricted group, eventually the indicators of the health
of the population returned to normal.179
This and similar discoveries have clearly revealed
that the claim by the proponents of punctuated equilibrium
theory that small populations are the source of evolution
has no scientific validity.
178 M. E. Soulť
and L. S. Mills, "Enhanced: No need to isolate genetics,"
Science, 1998, vol. 282, p. 1658.
179 R. L. Westemeier, J. D. Brawn, J. D.
Brawn, S. A. Simpson, T. L. Esker, R. W. Jansen, J. W. Walk,
E. L. Kershner, J. L. Bouzat, and K. N. Paige, "Tracking the
long-term decline and recovery of an isolated population",
Science, 1998, vol. 282, p. 1695.