Download File - Crystal Stephanie Taren

ANTH1020-015
Crystal Taren
Are Humans Still Evolving?
The previous Reflection I discussed wisdom teeth. The conclusion illustrated that
it was not only the selective pressures of consuming softer food, but change within the
jawbone structure, which yielded humans without these extra molars. This got me
thinking, are any populations in the world evolving? What are some examples? First one
must understand that evolution is “not a goal-oriented process”; it is merely the ability of
organism to adapt to its environment (Jurmain et al, 2012). This is important to note
because if an individual has made an adaptation it does not make them superior. Also you
put great emphasis on this in class, and it’s stated in the introduction of Chapter 6, and
within the article Balter wrote.
My initial source was “Are Humans Still Evolving?” by Michael Balter. I knew
this was a good start because it was published within a science journal, and I found it on
our class’s eReserves. Balter begins his the article making very good points about the
public’s interest in “evolutionary futures.” We are curious, but we lack the education
about the topic. The story of blondes going extinct was an effective way to prove the
point. The fact that the story was circulated so quickly relates to our class, because when
the term is finished I hope that I will understand the concepts well enough to participate
in meaningful discussions with others and recognize discrepancies when they appear in
the media.
From a macroevolutionary perspective humans have “changed the rules of the
game”(Balter 2005). Populations who reside in developed countries have had
technological and medical advancements that have changed “survival of the fittest, to
survival of everyone”(Balter 2005). Therefore adaptations are less frequently made
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Crystal Taren
within the individual, and the population has a lessened degree of natural selection. Some
say this essentially results in evolution stopping within developed countries.
Alternatively, natural selection still occurs in developed countries, but the main factors
are indicated by an individual’s fertility and fitness.
So what are implications for under developed countries? Balter’s article explains,
that the effects of natural selection are more detectable in underdeveloped countries due
to being able to identify the genes that may protect an individual from infectious diseases.
Since disease is more prevalent there are greater mortalities before reproductive age. My
secondary source was from an NPR interview with John Hawks, a professor of
anthropology, from the University of Wisconsin. Hawks and Balter both agree the
question of humans evolving should be restated as “how many kids are you having?”
Another commonality both authors used was lactase persistence within human
populations. It was reassuring that Hawks used this evidence because his interview was
more recent in comparison to Balter’s article from 2005. I had no idea humans are the
only species that continues to drink milk after being weaned from it. This example,
although simple, seemed to be the clearest to understand. We may not be making great
changes to phenotypes, but the majority of human evolution is happening on a more
subtle level with genotypes (Balter 2005).
Another piece of evidence is amylase (a gene in salvia that breaks down starches
into sugars). Apparently wheat wasn’t in our diets 20,000 years ago. In addition
populations who have been farming such grains have developed duplicated versions of
amylase to assist in the breakdown (Hawks 2013). This evidence is similar to the concept
of lactase persistence. What was even more fascinating was the idea of diet directly
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Crystal Taren
effecting evolution to the point of causing genes to change. It makes me wonder what are
the implications, other than obesity, of all the junk food Americans consume today. So to
answer my initial question are humans evolving the answer was yes, but not in the
science fiction type fashion I was hoping for. It is significant to note that lactase/amalyse
evidence is a microevolutionary change. If a human isn’t able to breakdown lactose and
grains, that will not result in their inability to reproduce, but it is a change that has
become common.
One of my favorite parts of Balter’s article is a statement from primatologist of
University of Calgary Mary Pavelka, “Many people see us continuing on the righteous
path of increasing intelligence, but we will not head in the direction of larger brains and
crania as long as infants are required to pass through a woman’s pelvis to get in to the
world.” Good to know considering one day I may decide to have a child. Subsequently,
many scientists are hesitant about making future predications about the human body
form. Rather they look at the selective pressure and traits human have derived from
chimpanzees, for example brain size. In addition when examining physical changes, not
all are due to natural selection. Height averages have increased, but it is not natural
selection in action. It is due to individual’s accessibility to better nutrition (Balter 2005).
Looking for an argument against this notion of human evolution was entertaining.
Yet, again, the Internet never fails when it comes to finding the answer that you want to
hear. According to David Attenborough, British naturalist and animal documentary
filmmaker, his explanation was that advances in birth control and family planning means
natural selection is no longer affecting modern-day humans. Attenborough called humans
"the only species to have put a halt to natural selection, of its own free will, as it were.”
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Crystal Taren
He then calls attention to the idea that populations are more influenced by “cultural
evolution.” In response to that I would explore Pavelka definition of natural selection
within developed countries, that is when reproduction occurs not all make the same
contribution, thus evolution is occurring.
ANTH1020-015
Crystal Taren
Sources Cited
Balter, Michael. 2005. Are Humans Still Evolving? Science, New Series, Vol. 309, No.
5732 pp. 234-237 http://www.jstor.org/stable/3842260
Bennet-Smith, Meredith. 2013. David Attenborough: Humans have Stopped Evolving
Because of Birth Control. http://www.huffingtonpost.com/2013/09/11/davidattenborough-humans-evolving-birth-control_n_3902277.html
Flathow, Ira. 2013. “Modern Humans Still Evolving and Faster than Ever”
http://www.npr.org/2013/09/27/226837803/modern-humans-still-evolving-andfaster-than-ever
Jurmain, Robert Kilgore, Lynn Trevathan, Wenda. 2012. Human Origins Evolution and
Diversity. p.3-22