In 1859 Charles Darwin’s The Origins of Species
was introduced to the world. Consequently, the study of life and where it came
from has not been the same since. For more than 150 years, Darwin’s work has been
evolving into a powerful and multi-faceted theory and has become the foundation
for many modern sciences. The basis of the evolutionary theory is that living
organisms can change over time and thus produce new species from this variation
– resulting in all species sharing a common ancestor that long ago made the
decision to crawl out of the primordial soup. When discussing evolution, it
should be stressed that individual organisms don’t evolve genetically – the
population that an organism belongs to can evolve as each generation contributes
different traits to the proverbial pool. The process of evolution can be
explained through Darwin’s three principles of evolution and the four processes
of evolution. Add to this the material evidence of evolution and one has reason
enough to believe the theory – fossil records clearly show that the process of evolution
is no longer merely a philosophy.
The first of Darwin’s three principles of
evolution is variability – meaning that “no two individuals are identical in
all respects” (Lavenda and Schultz 40). Variability plays a significant role in
evolution: it directly affects a species’ ability to adapt and survive in a
changing environment. Genetic variability means that there is a potential for a
genotype to change when exposed to environmental or genetic factors, thus
giving the organism’s offspring’s population an advantage when facing that
factor in the future.
Inheritability is the second of Darwin’s three
principles of evolution. Essentially, evolution occurs when inheritable traits
become more common or rare in a population: this can happen randomly through
mutations or genetic drift or non-randomly through natural selection, but the genes
transferred between populations and generations must be inheritable.
The third of Darwin’s principles, and the first
of the four processes of evolution, is that of natural selection. Evolution by
differential reproductive success (natural selection) is a two-step process:
first, random genetic information must be produced. Second, the specific traits
of an organism that are desirable – in other words – better suited to equip
them to meet the environmental challenges that they face and thus are more able
and likely to survive – are passed onto their offspring, and the cycle begins
again. As explained by Lavenda and Schultz, and according to Darwinian
principles, pandas got their “thumbs” (40) due to those with longer wrist bones
than others prevailing in the competition for bamboo to eat. These elongated
wrist bones made the process of gathering bamboo to eat far more efficient,
meaning that the pandas with said elongated wrist bones survived and had more
offspring than those with shorter wrist bones. This lead Darwin to conclude
that the varietals must have descended from a distant, common ancestor.
The second process of evolution is mutation.
Mutations occur when the form of a gene changes randomly. This unpredictability
is a divergence from the normal practice of stable gene inheritance, as they
are not goal-oriented. Mutations can be beneficial – like pesticide resistance
in insects or harmful – like cystic fibrosis in humans.
The third process of evolution is genetic drift
– which is an umbrella term encapsulating the founder effect and the bottleneck
effect. The founder effect is the loss of genetic variation that occurs when a
new population is established out of a larger population by a small number of
individuals. An example of the founder’s effect in humans can be found in the
Amish having higher than normal rates of polydactyl (extra fingers), due to the
Amish community being founded by a relatively small group with higher than
normal polydactyl rates. Because the Amish usually do not reproduce outside of
their community, the skewed allele frequency is maintained throughout
generations. The bottleneck effect is the potential loss of alleles after an
event such as disease or disaster greatly reduces the size of a population.
The fourth process of evolution is Gene flow
(the introduction of new genetic information). This transfer of alleles between
populations can be one-way, like a bee delivering pollen from a neighboring
field to another species of flower, or two-way, like two separate herds of deer
interbreeding. Gene flow is essential in the process of evolution as it
maintains variation within a population yet reduces variation between
populations on a larger scale.
As Steven Stanley, and evolutionary biologist,
states: “the theory of evolution is not just getting older, it is getting
better.” (32) When Darwin published The Origin of Species, the notion that all
life on earth being descended from a common ancestor was fiercely debated among
the scientists of that day. Today, there is no substantial scientific doubt
about the many close evolutionary links found between all organisms on earth. Evolution
is one of the most vital concepts in current science and supports and is supported
by many different fields of scientific study.