equilibrium theory of evolution, in its present state, holds
that living populations show no changes over long periods
of time, but stay in a kind of equilibrium. According to this
viewpoint, evolutionary changes take place in short time frames
and in very restricted populations-that is, the equilibrium
is divided into separate periods or, in other words, "punctuated."
Because the population is very small, large mutations are
chosen by natural selection and thus enable a new species
For instance, according to this theory, a species
of reptile survives for millions of years, undergoing no changes.
But one small group of reptiles somehow leaves this species
and undergoes a series of major mutations, the reason for
which is not made clear. Those mutations which are advantageous
quickly take root in this restricted group. The group evolves
rapidly, and in a short time turns into another species of
reptile, or even a mammal. Because this process happens very
quickly, and in a small population, there are very few fossils
of intermediate forms left behind, or maybe none.
On close examination, this theory was actually
proposed to develop an answer to the question, "How
can one imagine an evolutionary period so rapid as not to
leave any fossils behind it?" Two basic hypotheses
are accepted while developing this answer:
1. that macromutations-wide-ranging mutations
leading to large changes in living creatures' genetic make-up-bring
advantages and produce new genetic information; and
2. that small animal populations have greater
potential for genetic change.
However, both of these hypotheses are clearly
at odds with scientific knowledge.