Ranasaymon wrote:
Sajjad1994 GMATRockstar VeritasKarishma ChiranjeevSingh I am stuck between option A and D. Why is the primary purpose of the passage not D?
1. The primary purpose of the passage is to
P-1: Old view; Smart 1st-> then walk upright
New View: new discovery-> New view-> walk upright 1st-> smart(brain dev) next
p-2: Why upright?
lucy's similarity and dissimilarity with modern and with chimp
p3:
Why walk upright?
-> family theory
A. present an interpretation of the chronological relationship between bipedal locomotion and certain other key aspects of human evolution
D. analyze anatomical evidence of bipedal locomotion to show that the large brain of modern humans developed at a later stage of evolution than was previously believed
Anthropologists once thought that the ancestors
⠀⠀⠀ of modern humans began to walk upright because
⠀⠀⠀ it freed their hands to use stone tools, which they
⠀⠀⠀ had begun to make as the species evolved a brain of
(5)⠀⠀increased size and mental capacity. But discoveries
⠀⠀⠀ of the three-million-year-old fossilized remains of
⠀⠀⠀ our hominid ancestor Australopithecus have yielded
⠀⠀⠀ substantial anatomical evidence that upright walking
⠀⠀⠀ appeared prior to the dramatic enlargement of the
(10) brain and the development of stone tools. Says that bipedal walking came much earlier than previously believed (not that larger brain developed later than previously thought).
Bipedal walking happened before brain enlargement and tools development.
⠀⠀⠀⠀⠀⠀⠀⠀
Walking on two legs in an upright posture (bipedal
⠀⠀⠀ locomotion) is a less efficient proposition than walking
⠀⠀⠀ on all fours (quadrupedal locomotion) because several
⠀⠀⠀ muscle groups that the quadruped uses for propulsion
(15) must instead to provide the biped with
⠀⠀⠀ stability and control. The shape and configuration
⠀⠀⠀ of various bones must likewise be modified to allow
⠀⠀⠀ the muscles to perform these functions in upright
⠀⠀⠀ walking. Reconstruction of the pelvis (hipbones) and
(20) femur (thighbone) of “Lucy”, a three-million-year-old
⠀⠀⠀ skeleton that is the most complete fossilized skeleton
⠀⠀⠀ from the australopithecine era, has shown that they
⠀⠀⠀ are much more like the corresponding bones of the
⠀⠀⠀ modern human than like those of the most closely
(25) related living primate, the quadrupedal chimpanzee.
⠀⠀⠀ Lucy’s wide, shallow pelvis is actually better suited to
⠀⠀⠀ bipedal walking than is the rounder, bowl-like pelvis of
⠀⠀⠀ the modern human, which evolved to form the larger
⠀⠀⠀ birth canal needed to accommodate the head of a
(30) large-brained human infant. By contrast, the head of
⠀⠀⠀ Lucy’s baby could have been no larger than that of a
⠀⠀⠀ baby chimpanzee.Evaluates anatomical features which show that bipedal walking started much earlier and brains were small at that time.
⠀⠀⠀⠀⠀⠀⠀
⠀If the small-brained australopithecines were not
⠀⠀⠀ toolmakers, what evolutionary advantage did they
(35) gain by walking upright? One theory is that bipedality
⠀⠀⠀ evolved in conjunction with the nuclear family:
⠀⠀⠀ monogamous parents cooperating to care for their
⠀⠀⠀ offspring. Walking upright permitted the father to
⠀⠀⠀ use his hands to gather food and carry it to his mate
(40) from a distance, allowing the mother to devote more
⠀⠀⠀ time and energy to nurturing and protecting their
⠀⠀⠀ children. According to this view, the transition to
⠀⠀⠀ bipedal walking may have occurred as long as ten
⠀⠀⠀ million years ago, at the time of the earliest hominids,
(45) making it a crucial initiating event in human evolution.Questions why bipedal walking developed then if not to hold tools? It helped fathers carry food from a distance. So nuclear families started at that time and hence bipedal walking came into being.
Now consider:
1. The primary purpose of the passage is to
A. present an interpretation of the chronological relationship between bipedal locomotion and certain other key aspects
Correct. It is all about bipedal locomotion. It shows chronology of bipedal walking in relation to some other aspects - brain enlargement, tools development, nuclear family
D. analyze anatomical evidence of bipedal locomotion to show that the large brain of modern humans developed at a later stage of evolution than was previously believed
The passage doesn't focus on showing that brains evolved later. It shows that bipedal walking evolved earlier and discusses another factor that might have led to it.
Answer (A)
I missed the focused point by assuming that the brain evolved later. It's clear now. Thanks