▶ Your Answer :
In the given set of passages, there is some
discrepancy between the views of the author and the lecturer over the issue of
why the size of human brain decreased. The lecturer affirms that the size of
human brain has nothing to do with the changes in human society, human body size
and visual cortex, whereas the author in the reading passage suggests
otherwise. By giving three cogent explanations, the lecturer raises the
objections to the plausible hypotheses of the reading passage about why human
brain has decreased in size.
First of all, the lecturer debunks the
author’s first conjecture that as human societies change from the small groups,
which are self-sufficient, to the densified groups, in which members are not
required a wide range of duties, the large human brain was not been necessary.
To elaborate in detail, the lecturer claims that as the characteristics of
human society changed, new types of intelligent works have been newly required
for human. Additionally, he describes that those new tasks include highly
complex works dealing with relationships between people, demanding increase in
mental capacities. This shows a direct opposition to the reading passage.
Also, the lecturer indicates dissent over
the writer’s idea on the body size. The speaker sounds convinced that the
author is making manifest mistake because the shrinking rate of body size does
not match that of brain size. To be specific, the size of human body has
decreased in 8% in a certain period, while the size of the brain has decreased
in 16%. As the lecturer asserts, if the body and brain size are closely
related, the rates should have been similar. However, the author in the reading
passage contends that the discovery of bigger human brain 20,000 years ago demonstrates
well the fact that human brains became smaller because their controls on bodies
do not need large sized ones due to the body size shrinkage.
Finally, the lecturer goes on to expound
that the author’s final point about visual cortex, which processes information
in the brain, is also flawed. The lecturer argues, to corroborate this point, that
the visual cortex takes only small portion of the human brain and therefore, the
size of the visual cortex hardly affects the overall brain size. Additionally,
he mentions that brain contains not only cortex but also other elements that
are decreasing in size, and thus all the components should be considered.
However, the author asserts that as people hardly participate in
hunting-gathering, high level of visual acuity is not required anymore, and
this explains why human brain has shrunken along with the decreasing visual
cortex.
With these three convincing explanations
that the lecturer posits, the author’s three explanations about the reason for
the decrease in human brain size are all rendered invalid.
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