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Since prehistoric times, the average volume of the human

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Since prehistoric times, the average volume of the human [#permalink] New post 23 Nov 2012, 16:29
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Since prehistoric times, the average volume of the human brain has decreased significantly. Some scientists argue that
the shrinkage simply reflects diminishing human body mass during that period. Larger animals generally need larger brains
to control massive musculature. The musculature of the prehistoric modern humans known as Cro-Magnons was
greater than ours, but their brains were larger than ours and thus their ratio of brain volume to body mass roughly
equaled ours.

However, skeletal measurements show that brain volume shrank faster than body mass during certain periods. And
genetic analyses reveal that simultaneously, many genetic mutations affecting brain development spread, possibly
affecting humancognition. Some anthropologists have speculated that survival was less cognitively demanding in
agricultural societies thanhunter-gatherer societies, reducing pressures on brain size from natural selection. But
the shrinkage has occurred among all humans worldwide, in all types of societies.

A more plausible explanation is that our human ancestors unintentionally domesticated themselves. Less-aggressive
individuals may have provoked fewer unnecessary conflicts, improving their reproductive success in societies
demanding close cooperation. Like modern humans, domesticated mammals have smaller brains, flatter faces, smaller
teeth, and more gracefully slender builds than their wild ancestors. They are also less aggressive, allowing greater
integration with humans. All these characteristics may reflect simple genetic changes causing retention of certain
juvenile features into adulthood—changes easily spread by selective pressures.

Kindly explain ur choice please...

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

Q1:
The main purpose of the passage is to

A. argue that the average volume of the human brain has decreased significantly since prehistoric times
B. explain how our human ancestors unintentionally domesticated themselves
C. describe how the ratio of human brain volume to body mass has increased as a result of natural selection
D. present and assess the hypothesis that humans have become less aggressive as a result of diminished brain volume
E. discuss and evaluate three possible explanations of the shrinkage of the human brain

Q2:
To cast doubt on the idea that brain shrinkage has resulted solely from diminishing body mass, the author mentions

A. agricultural societies
B. massive musculature
C. prehistoric Cro-Magnons
D. genetic analyses
E. natural selection

Q3:
The passage most clearly indicates that compared to humans living today, at least some of our prehistoric ancestors
had

A. greater cognitive abilities
B. flatter faces
C. fewer unnecessary conflicts
D. larger teeth
E. less massive skeletons

Q4:
The passage most strongly suggests that at least in certain periods during or after Cro-Magnon times, humans created
certain conditions

A. that made survival less cognitively demanding than it had been for earlier humans
B. that demanded closer cooperation than modern societies demand
C. that gave a reproductive advantage to less-aggressive individuals
D. for the purpose of promoting their own domestication
E. to favor the domestication of mammal species that had relatively small brains and gracefully slender builds

Q5:
The main reason the author states that “the shrinkage has occurred among all humans worldwide”
(see highlighted text) is to support the implicit conclusion that

A. on average, human brains are equally powerful in all societies worldwide
B. lower cognitive demands in agricultural societies did not cause the shrinkage
C. survival was just as difficult in prehistoric agricultural societies as in hunter-gatherer societies
D. simultaneously many genetic mutations affecting brain development spread worldwide
E. pressures from natural selection favoring an increase in brain mass have been insufficient to prevent the shrinkage

Q6:
The main function of the third paragraph of the passage is to

A. argue for the author’s preferred explanation of human brain shrinkage
B. explain how reduced aggression among our prehistoric ancestors may have improved reproductive success
C. show how one possible explanation of certain observations is compatible with two other explanations presented
earlier in the passage
D. describe the characteristics that modern humans share with domesticated mammals
E. support certain hypotheses discussed earlier in the passage


Your invaluable explanations are welcome.
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Re: Since prehistoric times, the average volume [#permalink] New post 24 Nov 2012, 00:51
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Hii Bull.
I am not sure whether we would be facing 6 questions per passage, but let me tell you that these questions were, IMO, the most important types of questions one could face in the test.
My answer choices are E C A A B A.
let me know if reading has helped in gaining efficiency.

My notes for this passage:
paragraph 1:Average volume of brain, reduction, some scientists-->diminishing body mass, larger animals need larger brains. Same ratio
paragraph 2: a counterevidence and then an explanation, brain vlume sharnk faster than body mass, many genetic mutations spread affecting brain develpment.
paragraph 3: a better explanation for the shrinkgae of brain

Q-1)The question asks about the main purpose.
the author throughout the passage discussed and evaluated the three explanations.

Q-2)A weaken question here.
The author introduced Cro-Magnons and used the concept of ratio. So a C here.
Initially got stuck between musculature and Cro-Magnons but since the ratio of Magnons ahve been cited, I guess C weakens it.
Q-3)The passage most clearly indicates that compared to humans living today, at least some of our prehistoric ancestors
had:
Some anthropologists have speculated that survival was less cognitively demanding in
agricultural societies than hunter-gatherer societies
. It means that there were hunter gatherer societies who used brain for their protection and bla bla.
many genetic mutations affecting brain development spread, possibly
affecting humancognition
this suggests that hunter socities had more pressure and this yielded brain develpment spread, hence greater cognitive abilities.

Q-4) The passage most strongly suggests that at least in certain periods during or after Cro-Magnon times, humans created
certain conditions:
Switch to paragraph 2. As explained earlier, just as there were hunter based societies , agriculture based socities also existed. they didn't have to use their brain for survival in the forests and hence less pressure on brain. This made survival less cognitively demanding as compared to earlier humans when their was no agriculture. Hence A.

Q-5) This one is a good question. The author mentions "the shrinkage has occurred among all humans worldwide", to provide evidence that whether there was a pressure on brain or not, the shrinkage did occur. Had the lower cognitive demands lowered the brain size, then why did the brain size of humans in hunter based societies reduced.
B for me.

Q-6) The main function of the third para is to provide a better explanation. Proof-->The author introduces this paragraph by mentioning the line "a better plausible explanation is provided by.....".
Hence A.

So again, my answer choices are E C A A B A.
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Re: Since prehistoric times, the average volume of the human [#permalink] New post 08 Dec 2012, 11:40
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Hi Archit,

I disagree with you that A is a contender for the first question. I think it's an important distinction, so worth flagging.

Here is A
A. argue that the average volume of the human brain has decreased significantly since prehistoric times


Whilst this is certainly a core theme of the passage, it's not the main point. It is rather the pre-requisite fact for the passage. It is stated in the opening sentence (the average volume of the human brain has decreased significantly. ) and then we spend the rest of the 3 paragraphs discussing why it is the case. So there is actually no 'argument' over the volume decrease, it's a fact that we are discussing the reason behind. Hence E is the one...

E. discuss and evaluate three possible explanations of the shrinkage of the human brain

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Re: Since prehistoric times, the average volume [#permalink] New post 24 Nov 2012, 13:55
I must salute your courage and patience for taking the time for the in-depth analysis.
Meanwhile, the OA's are
[Reveal] Spoiler:
EDDCBA
.
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Re: Since prehistoric times, the average volume [#permalink] New post 06 Dec 2012, 11:15
gmatbull wrote:
I must salute your courage and patience for taking the time for the in-depth analysis.
Meanwhile, the OA's are
[Reveal] Spoiler:
EDDCBA
.



Can you please also post the explanations for answer choices? Thanks!
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Re: Since prehistoric times, the average volume of the human [#permalink] New post 07 Dec 2012, 02:49
My answers are
E C A A C A
though i marked E for the question in main purpose of the question but i feel that A is also a strong contender, the author seems to be advocating for the brain shrinkage with the explanation ... but the word evaluate mentioned in C is disputable, i dont agree to it. I dont find author evaluating anywhere in his explanation.
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Re: Since prehistoric times, the average volume of the human [#permalink] New post 08 Dec 2012, 12:43
Thanx Plumber
I understood my fault what about the rest of questions.
Both me and Marcab have identified same choices as answers but the OA posted by gmatbull is contradictory. do you agree if yes than can you pls describe.
Also what is the approach fro RC you suggest is best.
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Re: Since prehistoric times, the average volume of the human [#permalink] New post 08 Dec 2012, 12:54
Hi,

Got to dash out, but I'll do Q2 for now, which both of you seem to have struggled with. Here is my thought process:

To cast doubt on the idea that brain shrinkage has resulted solely from diminishing body mass, the author mentions
OK. So we are looking for a section that the author discusses the weaknesses in the argument that brain shrinkage has resulted solely from diminishing body mass
Here it is
However, skeletal measurements show that brain volume shrank faster than body mass during certain periods. And
genetic analyses reveal that simultaneously, many genetic mutations affecting brain development spread, possibly
affecting humancognition.


Why this section? The opening paragraph puts forward the argument that diminishing body mass, so this section at the beginning of the second paragraph is arguing against that first paragraph (key word: however) so is exactly what we want/color]

[color=#0000ff]Now take the 5 answer choices one by one and see which is mentioned (in this case word for word) in the relevant section


A. agricultural societies
B. massive musculature
C. prehistoric Cro-Magnons
D. genetic analyses
E. natural selection
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Re: Since prehistoric times, the average volume [#permalink] New post 09 Dec 2012, 07:16
pritish2301 wrote:
gmatbull wrote:
I must salute your courage and patience for taking the time for the in-depth analysis.
Meanwhile, the OA's are
[Reveal] Spoiler:
EDDCBA
.




Can you please also post the explanations for answer choices? Thanks!


Wow, I got all the answers right. These q were very tough. Where did you get it from?

I will post explanation once the boss of the house lets me back on the pc. She has had it with my gmat endeavours. ..

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Re: Since prehistoric times, the average volume of the human [#permalink] New post 09 Dec 2012, 19:37
I get question 4 and 5 wrong.
I do not understand oa in the question 4. anyone pls help explain.
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Re: Since prehistoric times, the average volume of the human [#permalink] New post 09 Dec 2012, 23:39
gmatbull wrote:
Since prehistoric times, the average volume of the human brain has decreased significantly. Some scientists argue that
the shrinkage simply reflects diminishing human body mass during that period. Larger animals generally need larger brains
to control massive musculature. The musculature of the prehistoric modern humans known as Cro-Magnons was
greater than ours, but their brains were larger than ours and thus their ratio of brain volume to body mass roughly
equaled ours.

However, skeletal measurements show that brain volume shrank faster than body mass during certain periods. And
genetic analyses reveal that simultaneously, many genetic mutations affecting brain development spread, possibly
affecting humancognition. Some anthropologists have speculated that survival was less cognitively demanding in
agricultural societies thanhunter-gatherer societies, reducing pressures on brain size from natural selection. But
the shrinkage has occurred among all humans worldwide, in all types of societies.

A more plausible explanation is that our human ancestors unintentionally domesticated themselves. Less-aggressive
individuals may have provoked fewer unnecessary conflicts, improving their reproductive success in societies
demanding close cooperation. Like modern humans, domesticated mammals have smaller brains, flatter faces, smaller
teeth, and more gracefully slender builds than their wild ancestors. They are also less aggressive, allowing greater
integration with humans. All these characteristics may reflect simple genetic changes causing retention of certain
juvenile features into adulthood—changes easily spread by selective pressures.

Your invaluable explanations are welcome.


Hi everyone posting the explanations as promised. Certain questions were pretty difficult even though the passage was very interesting...

Q1:
The main purpose of the passage is to

A. argue that the average volume of the human brain has decreased significantly since prehistoric times: False (Although there are certain arguments in the passage, the tone of the passage is certainly not centred around arguments, it is more or less like an evaluation of explanations)
B. explain how our human ancestors unintentionally domesticated themselves: False (Although, this has been mentioned in the essay in one paragraph, it is not the main theme of the essay. The reason this has been mentioned is to provide an explanation)
C. describe how the ratio of human brain volume to body mass has increased as a result of natural selection: False (There is no 'increase in brain to body mass ratio' mentioned anywhere in the passage)
D. present and assess the hypothesis that humans have become less aggressive as a result of diminished brain volume: False (This is mentioned in the passage just once not as a main theme but as an explanation for a point)
E. discuss and evaluate three possible explanations of the shrinkage of the human brain: True (main theme is brain shrinkage, the passage lists out exactly three explanations for the same, the authors also discusses and evaluates the explanations in all three paragraphs of the passage)

Q2:
To cast doubt on the idea that brain shrinkage has resulted solely from diminishing body mass, the author mentions
(Weaken, Brain Shrinking is due to Diminishing Body Mass)

A. agricultural societies: False (Agriculture was mentioned to show that brain shrinkage was uniform across all humans whether hunter or farmer)
B. massive musculature: False (Extremely tempting mislead, According to the passage author brings out the idea using this, but it not as a reason for the shrinkage to take place)
C. prehistoric Cro-Magnons: False (Again Cro-Magnon was mentioned as an example to demonstrate that the body size was shrinking so to did the size of the brain, it does not weaken or cast doubt that it was the sole reason for Brain Shrinkage)
D. genetic analyses: True (The section of the paragraph which mention this starts with "However", keyword. And right before however is mentioned the author talks about Brain size shrinking due to body mass decrease point. The excerpt from the passage "However, skeletal measurements show that brain volume shrank faster than body mass during certain periods. And genetic analyses reveal that simultaneously, many genetic mutations affecting brain development spread ...")
E. natural selection: False (Natural selection is mentioned with hunter - gatherer bit and has no direct link to cast doubt on the Brain Shrinking is due to Diminishing Body Mass argument)

Q3:
The passage most clearly indicates that compared to humans living today, at least some of our prehistoric ancestors
had

A. greater cognitive abilities: False (The passage says that we humans living today have lesser cognitive skilss, this was confusing for me because in reality I have always thought that modern humans have better cognitive skills. The hardest part in RC is detach your mind from the information we already know to only focus on the information given in the passage)
B. flatter faces: False (The passage says that domesticated animals and hence domesticated human might have flatter faces. The opposite, however, might be true)
C. fewer unnecessary conflicts: False (The passage says that modern humans are domesticated to have fewer conflicts and hence we have to assume that prehistoric men had more conflicts.)
D. larger teeth: True (Since the passage mentions that domestication causes domesticated animals to smaller teeth and hence domesticated humans have smaller teeth. We can assume that the vice versa is true for not so domesticated humans which refers to prehistoric man especially since the question provides some levee. Watch how carefully the question has been framed to ask "at least some of our prehistoric ancestors", At least some was the saviour for me.)
E. less massive skeletons: False (The passage clearly mentions that they had bigger skeletons)

Q4:
The passage most strongly suggests that at least in certain periods during or after Cro-Magnon times, humans created
certain conditions
(Humans created certain conditions = Humans domesticated themselves to do what?)

A. that made survival less cognitively demanding than it had been for earlier humans: False (Extremely misleading, but no. This part of the passage was mentioned to bring out that Brain size decreased evenly among hunters and gatherers)
B. that demanded closer cooperation than modern societies demand: False (Worded to confuse, but according to passage modern societes have the most co-operation amongst its people. There was no period in between in which there was better co-operation in societies according to the passage)
C. that gave a reproductive advantage to less-aggressive individuals: True (This is what gives the edge to domesticated humans, the ability to procreate efficiently. I finally understood why Casanova's were successful)
D. for the purpose of promoting their own domestication: False (Which reads out as humans domesticated themselves to domesticate themselves further, this is bullocks. Red herring Alert!!!)
E. to favor the domestication of mammal species that had relatively small brains and gracefully slender builds: False (What? Mammal species? Which species? Humans? Dogs? Ah, well never mind, out of scope)

Q5:
The main reason the author states that “the shrinkage has occurred among all humans worldwide”
(see highlighted text) is to support the implicit conclusion that

A. on average, human brains are equally powerful in all societies worldwide: False (Powerful? Worldwide? Out of scope)
B. lower cognitive demands in agricultural societies did not cause the shrinkage: True (Passage clearly mentions this in the second paragraph immediately after the bold section)
C. survival was just as difficult in prehistoric agricultural societies as in hunter-gatherer societies: False (Survival is not the major point over here, decrease in brain size is)
D. simultaneously many genetic mutations affecting brain development spread worldwide: False (Misleading. Since the word mutations is mentioned just before the bold section. The spreading of mutations were not talked about in the passage, its humans we are talking about not viruses.)
E. pressures from natural selection favoring an increase in brain mass have been insufficient to prevent the shrinkage: False (Truly Nonsense, utter bullocks!!!)

Q6:
The main function of the third paragraph of the passage is to

A. argue for the author’s preferred explanation of human brain shrinkage: True (The Author starts with "A more plausible explanation ..." and follows with positive evaluation unlike in other paragraphs. Esau was always Issac's favourite irrespective of what Jacob was told.)
B. explain how reduced aggression among our prehistoric ancestors may have improved reproductive success: False (Not really, this maybe a point in the paragraph but the main point would be to explain why the brain has been shrinking.)
C. show how one possible explanation of certain observations is compatible with two other explanations presented
earlier in the passage: False (No compatibility among the explanations. Sorry bud, nice try)
D. describe the characteristics that modern humans share with domesticated mammals: False (Not the main point of the paragraph, just a subpoint)
E. support certain hypotheses discussed earlier in the passage: False (Misleading, but too much ambiguity. There were many hypotheses, which one is this option talking about? I would give this as the right answer only if there weren't any strong answer choices around.)

Ok Guys, hope this helps... If you have better explanations please do share. Thanks.
Re: Since prehistoric times, the average volume of the human   [#permalink] 09 Dec 2012, 23:39
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