Questions 17 to 19 refer to the passage below. For each question, select one answer
choice, unless the instructions state otherwise.Determining whether an extinct species was bipedal has plagued
anthropologists for decades. While the structure of an organism’s
limbs and the arch of its feet are often noteworthy clues, the difficulty
of finding intact fossils of limbs and identifying the species to which
the limbs belong has limited the use of such inferences. Skulls, on the
other hand, can serve as an ideal proxy, since they are more commonly
found in the wild and because they provide a wealth of useful data to
determine their species of origin. However, the question of whether
skulls can actually provide useful data about bipedalism has been a
point of contention for decades. The most compelling evidence in favor
of this position comes from the foramen magnum, the large hole at the
base of the human skull through which the spinal cord passes. Since
Dart’s discovery of the “Taung Child,” there has been speculation that
a forward-shifted foramen magnum is an indicator of bipedalism,
since such a shift would have helped to balance the head atop the
spinal cord. But most of the arguments to date have been speculative,
drawing on just-so theories about the conditions that led to bipedalism
rather than empirical studies.
Fortunately, a new investigation by Russo and Kirk has lent
additional support to this link. To support the link between bipedalism
and a forward-shifting foramen magnum, Russo and Kirk first
identified the primary obstacle for proponents of their position: lack
of evidence across different species. So, instead of focusing only on
humans, they used advanced statistical methods to sample a wealth
of mammalian species. They discovered that the foramen magnum
in all bipedal mammals was, on average, more forward-positioned
than in quadrupedal mammals. Importantly, the researchers used
multiple tools and forms of measurements to draw their conclusion,
thereby eliminating possible objections about sample size or biased
methodology. Though not conclusive, the discovery of such a link
should strengthen anthropologists’ confidence in using skulls to
determine bipedalism. Future research should focus on investigating
ways to conduct controlled experiments on the benefits of a forward-
shifted foramen magnum.- The primary purpose of the passage is to
A explain a conflict and a resolution to that conflict
B explain the significance of a study
C question a standard scientific view
D describe the function of an anatomical feature
E provide a history of a debate
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