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Evolution in Everyday Life
In its simplest interpretation, the term ‘evolution’ means changing
gene frequencies through time. Whether or not you believe that
humans evolved from primates, understanding the concepts of
evolution and its significance to our everyday lives is essential. All
organisms evolve, and this can happen in more ways than one.
Humans have purposefully and accidentally caused organisms to
evolve through a variety of mechanisms including artificial
selection. Artificial selection is the process whereby desired traits
are encouraged and ultimately enhanced through generations of
selective breeding by humans.
Perhaps the best example of artificial selection is through the
large ears of corn that we know and love today. Corn is used
today for everything from livestock feed to human food to a sugar
substitute in processed foods. Most people do not realize that
corn started out as a completely different species known as
teosinte, which looked and tasted much different than today’s
varieties (Kingsley, 2005, University of Utah 2012).
Figure 1. Teosinte corn.
Teosinte, which still exists today, is
a bushier plant with a hard outer
shell casing over a much smaller
number of individual seeds.
Initially, most of the plant’s
resources seemed to have gone
into the vegetative portion of the
plant rather than the reproductive
stalk (Figure 1). These seed
casings are thought to have been a
protective covering for the seed to
help it last through the digestive
tract of animals that ate and
ultimately spread the seeds.
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Through generations of controlled crosses, believed to have been
conducted in Mexico, ear size and kernel number drastically
increased over time with plant height while the number of leaves
and stalks decreased and seed casings disappeared (Kingsley,
2005, University of Utah 2012).
Although this information seems obvious today,
no records were kept for these initial crosses,
and only through scientific experimentation have
researchers discovered the evolutionary history
of this plant. Modern day maize and teosinte are
genetically compatible and modern day hybrids
between them have characteristics of both and
are fertile (Figure 2). Controlled crosses in over
50,000 plants conducted by George Beadle
Figure 2.
Teosinte, Corn
indicated that the genetic differences between
and hybrid.
teosinte and maize comprise between 4-5
genes. Additional research through the
introduction of mutations into maize genomes give modern maize
plants characteristics of teosinte, which confirm Beadle’s initial
results (Kingsley, 2005, University of Utah 2012).
A second example of the power of artificial selection and directed
evolution exists today in the form of man’s best friend—dogs.
Fossil records reveal that dogs have been associated with
humans for over 130,000 thousand years and recognizable
changes and selection for certain traits can be recognized in
ancient Egyptian dog fossils. Initial fossils resembled today’s
wolves, and the Egyptians selected for sleeker and more
sophisticated looking traits that look like today’s saluki
breed. Today’s dog breeds vary in size, coat color, number of
teeth, leg length, snout size, ear size, and a seemingly infinite
number of additional characteristics. In fact, Charles Darwin
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pointed out that the skeletons of modern dogs are so different that
if they were found in the fossil record today, they would likely
be considered a different species (Figure 3) (Kingsley, 2005,
University of Utah 2012).
In the 1920’s and 30’s, Charles Stockard purchased a farm
(Cornell Anatomy Farm) and conducted breeding experiments,
using some of the
modern breeds that
had differential traits.
Stockard found that
the genetics of
individual traits
seems to be
relatively simple. He
also concluded that
different genes
seemed to control
the growth of
different bones, as
well as the fact that
artificial selection
Figure 3. Popular Dog breeds of 1912.
seems to be able to
drastically change phenotypes in relatively few generations
(Kingsley, 2005, University of Utah 2012).
In addition to artificial selection, which is a deliberate selective
force that humans have introduced, we as a species have
unintentionally caused many other organisms to evolve through
the use of antibiotics. Antibiotics include a variety of medications
prescribed to combat bacterial infection and are often prescribed
liberally by doctors for patients who are exhibiting signs of a
bacterial infection. Today, you may see antibacterial products
such as soaps, towelettes, and hand washes. What many do not
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realize is that this liberal use of antibiotics is driving bacteria to
evolve a resistance to these products, and the end result could be
deadly.
Antibiotics were first discovered in the 1929 by Alexander
Fleming. Fleming noticed that bacteria failed to grow in a Petri
plate, which had been taken over by a species of bread mold
called Penicillium (Figure 4). This led Fleming to conclude that the
mold created some substance that could
kill certain strains of bacteria. By the 1940s,
subsequent research led to the wide use of
this compound (called penicillin) by the
general public to combat bacterial infection
and sickness (Fisher 2012). The success of
penicillin is impressive, and after its initial
discovery, it was hailed as a miracle drug.
However, the discovery of penicillin was
Figure 4. Penicillium
only the beginning, and today there are
over 100 types of antibiotics and over 150
million antibiotic prescriptions are written each year (Stephens
2012). Despite this great success, recent discovery of new
antibiotics has slowed greatly, and recent research only seems to
improve existing antibiotics (BBC News 1999).
Figure 5. Staphylococcus
aureus
In addition to the lack of antibiotic
breakthroughs, a disturbing trend of
antibiotic resistant bacteria is on the
rise. As early as the 1940s, certain
strains of bacteria such as
Staphylococcus aureus (which causes
skin infections) were found to be
resistant to penicillin (Fisher 2012)
(Figure 5). Over time, doctors are
noticing more and more infections that
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are becoming increasingly difficult to treat. For example Klebsiella
pneumoniae, which had infected a patient in an intensive care unit,
was found to be resistant to every type of antibiotic that the
hospital had (Groopman 2008). For the most part, these
outbreaks seem to be confined to the places where antibiotics are
used
most often including hospitals and nursing homes. However,
deaths from drug resistant bacterial infections are being reported
in community settings including football teams and Hurricane
Katrina evacuees (Groopman 2008). At this point, the only
resistance against these bacterial infections has been our own
immune system, which evolved long ago as a response to such
infections. Perhaps it is not too surprising that the best defense
against evolving strains of bacteria is a system that has been
perfected over millions of years of evolution.
Works Cited
BBC News. 1999. A brief history of antibiotics. Retrieved from:
http://news.bbc.co.uk/2/hi/health/background_briefings/antibiotics/
163997.stm
Fisher, M.C. The History of Antibiotics. Retrieved from:
http://www.healthychildren.org/English/healthissues/conditions/treatments/pages/The- History-ofAntibiotics.aspx?nfstatus=401&nftoken=00000000-0000-00000000000000000000&nfstatusdescription=ERROR%3a+No+local+toke
n
Groopman, J. 2008. Superbugs. The New Yorker, Retrieved from:
http://www.newyorker.com/reporting/2008/08/11/080811fa_fact_g
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roopman.
Kingsley, 2005. HMMI Holiday Lecture Series, Evolution:
Retrieved from:
http://www.hhmi.org/biointeractive/evolution/lectures.html
Stephens, E. 2012. WebMD. Retrieved from:
http://www.emedicinehealth.com/antibiotics/article_em.htm
University of Utah, 2012. Learn Genetics. Retrieved from:
http://learn.genetics.utah.edu/
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