The punctuated 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 to emerge.
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.
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