Evolution has been in action since the presence of life here on Earth, but it was not until 1859 when
Charles Darwin published On the Origin of Species by Means of Natural
Selection that the concept of evolution was known by us, humans. Darwin has
collected data and evidences that evolution was caused primarily by natural
selection, but he never arrived at a clear, unambiguous interpretation of the
phenomena of inheritance and variation.
The Birth of Neo-Darwinism
Not a decade later, Mendel’s
work Experiment on Plant Hybridization was eventually published in 1866
in the Proceedings of the Natural Science Society of Bruno, where he
established that traits do not mix or blend, but segregate in the formation of
the gametes. Contrary to the widely known and accepted theory at that time –
the blending theory which predicted that sexual reproduction will result in a
homogenization of a population that may result to rapid loss of variations
within populations.
Many years after Mendel’s
publication, his theory of genetics as the basis for biological inheritance,
and mathematical population genetics was integrated in Darwin’s concept of evolution.
Hence, Neo-Darwinism was born – backed up with concepts in genetics to further
help us understand how and why organisms have undergone evolution.
Genetic Explanation of
Evolution
Evolutionary genetics is the
study of how genetic variation leads to evolutionary change. This field of
study has modified the definition of “selection” which previously referred to
the survival of superior traits (traits necessary for organism’s survival), while
other traits are disposed. By now, we know that this, indeed, is not true. Although
superior traits are more visible in nature since they have helped organisms
adapt and survive in ever-changing environments, other traits are still present,
variations are still observable, and certain diseases (inherited or not) still
exist.
The “superior” trait is
redefined as the “fit” trait. A trait can either be dominant or recessive and
its fitness is dependent on the inheritance of the recessive trait to the next
generations. Fitness is relative to the environment where selection happens. Consider
a grasshopper species with brown and green variants: in a grassland
environment, green grasshoppers have an advantage to camouflage on the green
grasses and be less visible to its predators. In contrast, the brown
grasshoppers are more visible, which increases the risk of being seen and
eaten by their predators. Consequently, more green grasshoppers will survive
and continue their life cycle to produce more offspring with the inherited
trait of being green-colored. In this case, the trait for the green-colored
grasshopper is more fit than the trait for brown color. The varying fitness of
traits fuels the change in gene frequencies of populations which can cause more
variations in the population.
Branches of genetics such as
molecular, developmental, and population genetics have been great contributors
to the science of genetics and evolutionary biology, and according to Lewontin,
it has done so through three paths:
- Population and biometrical genetics have shown that there is considerable heritable variation in virtually any population, on which selection may act, which also proved that selection has not exhausted variation.
- Molecular and developmental genetics have elucidated how new heritable variation can arise and provide the basis for genetic novelties beyond the limits of variation that already exists.
- Developmental and population genetics have vastly enriched our knowledge, so we know now that there are other evolutionary forces other than simple selection which can explain the diversity and continued diversification of organisms.
Evolutionary genetics gave us
knowledge on how and why organisms have evolved. Aside from knowing our past
through studying our ancestors and the changes they have gone through,
evolutionary genetics can also give us insights about the fate of different
organisms in the future.
Posts
0 Comments