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Questionable OG12 CR

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Questionable OG12 CR

by chieftang » Sat Dec 10, 2011 4:34 pm
In Swatkans territory, archaeologists discovered charred bone fragments dating back one million years. Analysis of the fragments, which came from a variety of animals, showed that they had been heated to temperatures no higher than those produced in experimental campfires made from branches of white stinkwood, the most common tree around Swartkans.

Which of the following, if true, would together with the information above, provide the best basis for the claim that the charred bone fragments are evidence of the use of fire by early hominids?

(A) The white stinkwod tree is used for building material by the present day inhabitants of Swartkans.

(B) Forest fires can heat wood to a range of temperatures that occur in campfires.

(C) The bone fragments were fitted together by the archaeologists to form the complete skeletons of several animals.

(D) Apart from the Swartkans discovery, there is reliable evidence that early hominids used fire as many as 500,000 years ago.

(E) The bone fragments were found in several distinct layers of limestone that contained primitive cutting tools known to have been used by early hominids.

OA to come.
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by GMATGuruNY » Sun Dec 11, 2011 12:32 am
chieftang wrote:In Swatkans territory, archaeologists discovered charred bone fragments dating back one million years. Analysis of the fragments, which came from a variety of animals, showed that they had been heated to temperatures no higher than those produced in experimental campfires made from branches of white stinkwood, the most common tree around Swartkans.

Which of the following, if true, would together with the information above, provide the best basis for the claim that the charred bone fragments are evidence of the use of fire by early hominids?
This CR exhibits a language shift.
The premise is about X: BONE FRAGMENTS.
The conclusion is about Y: EARLY HOMINIDS.

In the premise, the BONE FRAGMENTS are connected to fire.
In the conclusion, EARLY HOMINIDS are connected to fire.
The assumption is that there is a LINK between the BONE FRAGMENTS and EARLY HOMINIDS.
The correct answer choice will strengthen this link.

(A) The white stinkwood tree is used for building material by the present day inhabitants of Swartkans. Outside the scope. The argument is about EARLY HOMINIDS, not the PRESENT DAY inhabitants. Eliminate A.

(B) Forest fires can heat wood to a range of temperatures that occur in campfires. Weakens the conclusion. By implying that the charring of the bone fragments might have been caused not by a campfire but by a FOREST FIRE, this answer choice BREAKS THE LINK between the BONE FRAGMENTS and EARLY HOMINIDS. Eliminate B.

(C) The bone fragments were fitted together by the archaeologists to form the complete skeletons of several animals. Does not connect the BONE FRAGMENTS to EARLY HOMINIDS. Eliminate C.

(D) Apart from the Swartkans discovery, there is reliable evidence that early hominids used fire as many as 500,000 years ago. Outside the scope. The passage is about bone fragments dating back ONE MILLION years. This answer choice does not connect the BONE FRAGMENTS to EARLY HOMINIDS. Eliminate D.

(E) The bone fragments were found in several distinct layers of limestone that contained primitive cutting tools known to have been used by early hominids. Correct. This answer choice strengthens the link between the BONE FRAGMENTS and EARLY HOMINIDS.

The correct answer is E.
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by chieftang » Sun Dec 11, 2011 8:05 am
Ya, see I find this one very questionable. The OA is E.

From the question statement: evidence of the use of fire by early hominids. Not by hominids of 1M years ago. Just early hominids. And not the use of "tools" by hominids. The use of fire by early hominids.

Choice D deals with both the use of fire and early hominids.

To me the use of "primitive cutting tools" by early hominids was out of scope. However, I clearly see your reasoning and suspect this language shift technique is common on the GMAT. To me it's rather shifty, but clearly it needs to be recognized!!

Thanks.
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by GMATGuruNY » Sun Dec 11, 2011 8:23 am
chieftang wrote:Ya, see I find this one very questionable. The OA is E.

From the question statement: evidence of the use of fire by early hominids. Not by hominids of 1M years ago. Just early hominids. And not the use of "tools" by hominids. The use of fire by early hominids.

Choice D deals with both the use of fire and early hominids.

To me the use of "primitive cutting tools" by early hominids was out of scope. However, I clearly see your reasoning and suspect this language shift technique is common on the GMAT. To me it's rather shifty, but clearly it needs to be recognized!!

Thanks.
The correct answer must support not only the conclusion but also HOW THE PREMISE IS BEING USED to support the conclusion.
This CR is using the BONE FRAGMENTS to connect EARLY HOMINIDS to FIRE -- a connection that is valid ONLY if the BONE FRAGMENTS are linked to EARLY HOMINIDS.
Answer choice E provides this missing link.
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by satishchandra » Tue Dec 13, 2011 1:29 am
Mitch,
As you rightly said, 'E' connects The bone fragments to early hominids.

Ideally, 'E' should speak about the evidence about BONE FRAGMENTS+FIRE used by EARLY HOMINIDS
In actual, E speaks ONLY about BONE FRAGMENTS used by EARLY HOMINIDS

As per the wording given in answer choice 'E', it appears to me, BONE FRAGMENTS were used by EARLY HOMINIDS PERHAPS not for the USE of FIRE but for the USE of making some tools
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by chieftang » Tue Dec 13, 2011 7:49 am
satishchandra wrote:Mitch,


As per the wording given in answer choice 'E', it appears to me, BONE FRAGMENTS were used by EARLY HOMINIDS PERHAPS not for the USE of FIRE but for the USE of making some tools
That was, and still is, my concern with this one. Answer E has nothing to do with fire. On the other hand, answer D deals with fire but not with the use of fire 1,000,000 years ago. The more I study, the more I realize a pattern in GMAT answer choices though. You simply can't assume to know the definition of "early". If the stimulus states a timeframe (1M years ago in this case) and an answer choice contains a different timeframe (0.5M years ago in the case of D here), then that answer is seemingly always incorrect.
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by GMATGuruNY » Tue Dec 13, 2011 8:34 am
chieftang wrote:
satishchandra wrote:Mitch,


As per the wording given in answer choice 'E', it appears to me, BONE FRAGMENTS were used by EARLY HOMINIDS PERHAPS not for the USE of FIRE but for the USE of making some tools
That was, and still is, my concern with this one. Answer E has nothing to do with fire. On the other hand, answer D deals with fire but not with the use of fire 1,000,000 years ago. The more I study, the more I realize a pattern in GMAT answer choices though. You simply can't assume to know the definition of "early". If the stimulus states a timeframe (1M years ago in this case) and an answer choice contains a different timeframe (0.5M years ago in the case of D here), then that answer is seemingly always incorrect.
We cannot connect what was true 500,000 years ago to what might have been true 1,000,000 years ago. A lot can change in 500,000 years.

Another issue: The conclusion of the argument is not that early hominids used fire but that THE CHARRED BONES FRAGMENTS ARE EVIDENCE of the use of fire by early hominids. Thus, the correct answer cannot establish a direct link between early hominids and fire; to do so would render the charred bones irrelevant. Instead, the correct answer must support the use of the CHARRED BONES as EVIDENCE. By linking early hominids to the charred bones -- which the passage has already linked to fire -- answer choice E supports the conclusion that THE CHARRED BONES FRAGMENTS ARE EVIDENCE OF THE USE OF FIRE BY EARLY HOMINIDS.
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by chieftang » Tue Dec 13, 2011 10:34 am
GMATGuruNY wrote:
We cannot connect what was true 500,000 years ago to what might have been true 1,000,000 years ago. A lot can change in 500,000 years.
Heh. Completely agree. But what threw me was the statement "early" hominids. I took "early" to mean that a precise time period wasn't important. I.e. 500k years, 1M years... both "early". But then, of course, where do you draw the line between early and not early? I'm no anthropologist. ;-)
Another issue: The conclusion of the argument is not that early hominids used fire but that THE CHARRED BONES FRAGMENTS ARE EVIDENCE of the use of fire by early hominids.
Charred bone fragments are also evidence of a dry lightening strike that caused a massive conflagration and mass casualties. :-) The existence of hominids and the existence of charred bone fragments is kind of a weak link. But I definitely see your point. Weak evidence is still evidence. :-) But why would they throw in the tidbit about tools in the correct answer? Is that a slight of hand trick?

Thus, the correct answer cannot establish a direct link between early hominids and fire; to do so would render the charred bones irrelevant. Instead, the correct answer must support the use of the CHARRED BONES as EVIDENCE. By linking early hominids to the charred bones -- which the passage has already linked to fire -- answer choice E supports the conclusion that THE CHARRED BONES FRAGMENTS ARE EVIDENCE OF THE USE OF FIRE BY EARLY HOMINIDS.
I definitely see your point. Thanks again!
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