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Over the past 20,000 years, the average volume of the human male brain

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Over the past 20,000 years, the average volume of the human male brain  [#permalink]

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New post 04 Oct 2018, 18:36
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Over the past 20,000 years, the average volume of the human male brain has decreased from 1,500 cubic centimeters to 1,350 cc, losing a chunk the size of a tennis ball. The female brain has shrunk by about the same proportion. If our brain keeps dwindling at this rate over the next 20,000 years, it will start to approach the size of the brain found in Homo erectus, a relative that lived half a million years ago and had a brain volume of only 1,100 cc.

Some believe the erosion of our gray matter means that modern humans are indeed getting dumber. A common measure of intelligence - the encephalization quotient or EQ, defined as the ratio of brain volume to body mass - has been found to be decreasing in the recent past. Recent studies of human fossils suggest the brain shrank more quickly than the body in near-modern times. More importantly, analysis of the genome casts doubt on the notion that modern humans are simply daintier but otherwise identical versions of our ancestors, right down to how we think and feel. Another study concluded that our present EQ is the same as that of the Cro-Magnons - our ancestors who lived 30,000 years ago in Europe and were known more for brawniness rather than brilliance.

On the other hand, other anthropologists such as Hawks believe that as the brain shrank, its wiring became more efficient, transforming us into quicker, more agile thinkers. They explain the shrinking by arguing that over the very period that the brain shrank, our DNA accumulated numerous adaptive mutations related to brain development and neurotransmitter systems—an indication that even as the organ got smaller, its inner workings changed.

This explanation may be plausible, considering that the brain is such a glutton for fuel that it globs up to 20% of all the calories. To optimize this, the evolution may be moving towards a more efficient smaller brain that yields the most intelligence for the least energy. A boom in the human population in the last 20,000 years ago greatly improved the odds of such a fortuitous development since the more the individuals, the bigger the gene pool, and the greater the chance for an unusual advantageous mutation to happen.

The man-made product that is closest to the brain, the microprocessor, has seen similar evolution. A microprocessor consists of transistors- the human equivalent of neuron that participates in decision making – connected with wires that act as messengers between neurons. The first microprocessors had extremely simple architectures and were not optimized for a certain set of tasks but were more general purpose. Consequently, a lot of the power they consumed was dissipated in internal wiring and not in decision making. With refinements, the architectures became more and more attuned to the tasks that the microprocessor most commonly needed to do. Consequently, for the same number of transistors the amount of wiring decreased by a factor of 3 while the microprocessor’s processing speed increased by a factor of 10. While active research is still to conclude whether the same holds true in case of the brain, one can only hope that the results are along the lines of the microprocessor.


1. The passage suggests that the modern microprocessor is more efficient because:

A. It has more transistors and fewer wires.

B. It contains transistors that are smaller in size and consume less power.

C. It contains transistors that became faster with the evolution of technology.

D. Over the years, the organization of wiring and transistors has been better optimized for tasks that the microprocessor is most commonly required to perform.

E. The prevalence of precision manufacturing has allowed more transistors to be added to the microprocessor.

2. In paragraph 4 - lines 1 and 2, the author talks about the brain being a glutton for fuel to:

A. justify the reason that evolution may be moving in a particular direction.

B. stimulate discussion about an alternate hypothesis proving the negative aspects of the reduction of brain volume.

C. provide supporting evidence for a controversial theory.

D. refute the conclusion of the hypothesis mentioned in the preceding paragraph.

E. draw a parallel to another evolutionary development with a similar impact.

3. According to the passage, the relationship between encephalization quotient and brain volume is:

A. for the same weight, the higher the brain volume the higher the encephalization quotient.

B. for the same weight, the lower the brain volume the higher the encephalization quotient.

C. the higher the weight the higher the encephalization quotient.

D. the higher the encephalization quotient the higher the brain volume.

E. the lower the encephalization quotient the higher the brain volume.

4. Which of the following if true would weaken the assertion that humans are getting dumber with the erosion of brain volume?

A. A study proved that our ancestors with lower encephalization quotient were more intelligent than our ancestors with higher encephalization quotient.

B. A discovery that showed that through more refined training methods, a 20 year old can perform many more tasks than a 20 year old could do 500 years back.

C. A study that proves that there is positive but non-linear correlation between encephalization quotient and human intelligence.

D. A study that discovered that human encephalization quotient increased at a staggering pace 10000 years back.

E. A study that proves that there are measures outside of encephalization quotient that makes humans more productive.


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Re: Over the past 20,000 years, the average volume of the human male brain  [#permalink]

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New post 04 Oct 2018, 18:59

+1 kudos to the posts containing answer explanations of all questions


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Re: Over the past 20,000 years, the average volume of the human male brain  [#permalink]

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New post 04 Oct 2018, 19:48
I would like to have the explanation of A being the answer for Q2.
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Re: Over the past 20,000 years, the average volume of the human male brain  [#permalink]

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New post 04 Oct 2018, 22:33
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JigarB wrote:
I would like to have the explanation of A being the answer for Q2.


It is stated in the highlighted part that - the evolution may be moving towards a more efficient smaller brain that yields the most intelligence for the least energy.

A. justify the reason that evolution may be moving in a particular direction.
Uses the same line of thought. Let's keep this option.

B. stimulate discussion about an alternate hypothesis proving the negative aspects of the reduction of brain volume.
Previous paragraph (which is continuation to the highlighted part) states that the brain reduction is a positive aspect instead. Eliminated.

C. provide supporting evidence for a controversial theory.
There exist no controversial theory. So this option is also out.

D. refute the conclusion of the hypothesis mentioned in the preceding paragraph.
Refute = prove wrong.
Brain being a glutton for fuel is supporting the hypothesis stated in the preceding paragraph. Eliminated.

E. draw a parallel to another evolutionary development with a similar impact.
No evolutionary development with a similar impact has been decribed in the passage. Out of scope. Eliminated.

Therefore the answer is A. Hope it is clear :)
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Re: Over the past 20,000 years, the average volume of the human male brain  [#permalink]

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New post 07 Oct 2018, 00:35
Can't the answer for 4 be E..Debunking the theory of EQ will not weaken the assertion?
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Re: Over the past 20,000 years, the average volume of the human male brain  [#permalink]

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New post 09 Oct 2018, 02:59
for question 4: why not B?

4. Which of the following if true would weaken the assertion that humans are getting dumber with the erosion of brain volume?

A. A study proved that our ancestors with lower encephalization quotient were more intelligent than our ancestors with higher encephalization quotient.
My explanation: Option NOT Relevant
Reason: The first para says that the average volume of the human male brain has decreased over the period. The option A doesn't call out explicitly that our ancestors @ 20000 yrs had better IQ than our ancestors @10000 yrs. There statement doesn't indicate that over the years, even though size is reduced, the EQ was shown higher. so this option doesn't weaken the assertion.

B. A discovery that showed that through more refined training methods, a 20 year old can perform many more tasks than a 20 year old could do 500 years back.
My explanation: Relevant, keep it
Reason: As per the question, we need to find an assertion that would weaken. If training methods can improve the performance, then reducetion of brain size, over the years, will not matter.

C. A study that proves that there is positive but non-linear correlation between encephalization quotient and human intelligence.
My explanation: Option NOT Relevant
Reason: The non-linear correlation will not weaken the assertion. If it's a positive Non-linear correlation does not necessarily mean humans are getting wiser. Not relevant.

D. A study that discovered that human encephalization quotient increased at a staggering pace 10000 years back.
My explanation: Option NOT Relevant
Reason: With a constant brain volume, The EQ will continue increasing if the body mass is decreased. This option is Not weakening.

E. A study that proves that there are measures outside of encephalization quotient that makes humans more productive.
My explanation: Option NOT Relevant
Reason: Productivity is not under discussion. Not relevant.

with above analysis, i thought option B looked promising. Please suggest what am i missing?
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Re: Over the past 20,000 years, the average volume of the human male brain  [#permalink]

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New post 09 Oct 2018, 10:42
Cinematiccuisine wrote:
for question 4: why not B?


Hey Cinematiccuisine,

Let me give you my line of reasoning. Option B is out of scope. If you're still not convinced, think about the below points related to option B.

* Says people can be trained to perform tasks. We cannot co-relate training and intelligence. Even animals/kids can be trained to do certain tasks, yet we can't conclude their intelligence has increased.

* Talks only about people aged 20. The sample set is not representative enough.

4. Which of the following if true would weaken the assertion that humans are getting dumber with the erosion of brain volume?

If you look at paragraph 2, there is an assertion that as the EQ of brain decreases, the brilliance also decreases(Evident in the last line of para 2). Option A directly weakens the claim by providing data that such assertion need not be true. Hope it helps!

Cheers!
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Re: Over the past 20,000 years, the average volume of the human male brain &nbs [#permalink] 09 Oct 2018, 10:42
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Over the past 20,000 years, the average volume of the human male brain

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