Biology Reference
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“noncoding” DNA segments. All of these hypotheses may be considered under the
intellectual umbrella of the neoDarwinian paradigm.
All of the theories that consider evolution as a result of mechanisms other than (or
in addition to) changes in the genetic information may be included in the epigenetic
group of hypotheses. Some of these epigenetic hypotheses attempt to explain only
specific aspects of evolution and some accept the role of genetic mutations as a com-
plementary cause of evolutionary change.
Having resolved the theoretical problems of selecting useful evolutionary
changes, the crux of the problem that any hypothesis on the evolution of the organic
world currently faces is identifying the ultimate source of the information for evo-
lutionary change. This is the sum and substance of the evolution theory and it is
the criterion I am applying for the classification of several hypotheses of evolution
reviewed briefly below.
The Modern Synthesis—The neoDarwinian Hypothesis of
Evolution
Despite its limitations, the modern synthesis that emerged by the early 1930s from
the eclectic merger of Darwinian doctrine with classical genetics remains the most
widely accepted paradigm. Essentially, the modern synthesis posits that the evolution
of living organisms results from the action of natural selection on existing genetic
variations, including the occurrence of new gene mutations and genetic recombina-
tions. The genetic variations produce microevolution that is evolution at the molec-
ular and cellular levels. Accumulation of microevolutionary changes, under the
action of natural selection and over time, may lead to macroevolutionary changes
(i.e., evolution at the level of species and higher taxonomic ranks). Both microevolu-
tion and macroevolution depend on the same process of selecting genetic variations.
Speciation, the formation of a new species, is primarily related to the geographic
isolation of populations (allopatric speciation), which is the cause of genetic (prezy-
gotic and postzygotic) isolation or the reproductive isolation of populations, even if
they come into contact again.
The neoDarwinian synthesis focused primarily on developing a mathematical
apparatus to study allele frequencies and their selection in populations. Taking the
role of changes in allele frequencies for granted, the modern synthesis did not try to
show, even theoretically, how these changes in allele frequencies may induce evolu-
tionary changes, especially in morphology, at both subspecific and supraspecific lev-
els. The paradigm posits that natural selection produces order from the randomness
of changes in genes. But natural selection first comes to the stage after the emer-
gence of the adaptive change. What we need to know is not how the evolutionary
changes in morphology, life history, and behavior are selected but how they arise.
What is the mechanism behind the evolutionary change?
It should be pointed out, however, that the identification of the Darwinian vari-
ability with spontaneous gene mutations or genetic variability in general (existing
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