A favored theory to explain the extinction of dinosaurs, together with

Question

A favored theory to explain the extinction of dinosaurs, together with many other species, has been the globally catastrophic collision of a large asteroid with the Earth. Supporting evidence is an extraterrestrial chemical element in a layer of dust found worldwide at a geological level laid down contemporaneously with the supported event. A new competing theory contends that any asteroid impact was irrelevant, because it was massive volcanic activity that caused the extinctions by putting enough dust into the atmosphere to cool the planet. The Deccan region of India contains extensive volcanic flows that occurred within the same time period as the supposed asteroid impact and the extinctions.

Which one of the following, if true, most strongly indicates that the asteroid-impact theory is at least incomplete, if not false?

(A) Large concentrations of dinosaur nests with fossil eggs found in Alberta indicate that at least some species of dinosaurs congregated in large groups during some part of their lives.

(B) Dinosaur remains indicate that some species of dinosaur could have migrated in herds over wide ranges, so that they could have traveled to escape the local effects of certain catastrophes.

(C) Legends from many cultures, such as the Greek legend that Cadmus raised an army by sowing dragons’ teeth in the ground, show that various ancient peoples worldwide were familiar with the fossils of dinosaurs.

(D) In the Gobi desert in China, where now only small animals can eke out an existence, fossil dinosaur skeletons 27 feet long were found in circumstances indicating that the climate there was as dry when the dinosaurs lived as it is now.

(E) The fossil record in Montana from below the layer of extraterrestrial dust shows a diminution over time in dinosaur species from 35 to 13, and dinosaur teeth found above the dust layer show a diminution in species from 13 to 5.

Source: LSAT

Same passage with different stem question:  LINK

Skywalker18 · Accepted Answer

We're looking for the answer choice that most strongly suggests that the theory that the asteroid impact caused the dinosaurs' extinction is no good. How does (E) fit the bill?

Well, what (E) suggests is that dinosaur species were dying off precipitously before the asteroid hit (because layers of dust beneath the asteroid dust would have to have been formed earlier than the asteroid dust), and continued to do so afterward. The most important part here is that the lion's share of species extinctions occurred, according to (E), before the asteroid impact! If that's the case, the asteroid couldn't have been the main cause of the extinctions.

Does that make sense? Remember, the theory we're seeking to undermine is not the theory that there was an asteroid impact. Whether there was an impact is not in question. The issue is, did the impact cause the dinosaurs to go extinct?

As for the other answers:

(A) is way out of scope. How does this affect the asteroid theory?

(B) is tempting, but we're told that the asteroid impact was "globally catastrophic." So we don't care whether dinosaurs could escape some local catastrophes.

(C) is going, going, gone! Way out of scope!

(D), yeah, it's out of scope. Who cares about climates in the Gobi desert?

sobby · Answer

By POE , I will go with E ..As the fossil record is found both top and below the extraterrestrial dust, it strengthens the point that there may be some other catastrophic event that led animal extinction ..

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sunny91 · Answer

Hi Broall,
Can u kindly explain option E. I felt Option D somehow suggests volcanic activity is not the reason. As the region is almost as dry now as it was earlier, and so there is no cooling effect and thus we cant ignore the asteroid theory.

TaN1213 · Answer

Clearly E.
Only E provides support to both the theories without refuting one. D refutes the second theory(dust has resulted in cooling of the planet) stating that the temperature hasn't changed. 
E provides evidence that both the theories have impacted in extinction because the fossil both above and below the extraterrestrial dust layer shows diminution.

sunny91 · Answer

Hi Tan123,
Can u kindly explain that how E supports both the theories?

Leo8 · Answer

Supporting evidence is an  extraterrestrial chemical element in a layer of dust  found worldwide at a geological level laid down contemporaneously with the supported event.

A new competing theory contends that any asteroid impact was irrelevant, because it was massive volcanic activity that caused the extinctions  by putting enough dust into the atmosphere to cool the planet.

what is E saying

(E) The fossil record in Montana from  below the layer of extraterrestrial dust  shows a diminution over time in dinosaur species from 35 to 13, 
 and dinosaur teeth found  above the dust layer show  a diminution in species from 13 to 5.

By this statement - we can infer there were two layers of two different composition of dust.

first layer - -- layer of dust formed by the volcanic activity

second layer - layer of dust formed by extraterrestrial chemical element

hence it is supporting both the theories of extinction.

jawele · Answer

E basically says that the dinosaurs were wiped out at much faster pace before the extraterrestrial dust laid down on the surface than after it appeared on the surface. Thus this suggests that the extinction was started by something else.

(E) The fossil record in Montana from below the layer of extraterrestrial dust shows a  diminution  over time in dinosaur species from 35 to 13 ( effect: 22 ), and dinosaur teeth found above the dust layer show a  diminution  in species from 13 to 5 ( effect: 8 ).

TheNightKing · Answer

Skywalker18

That's some IPL (Cricket if you don't know what I mean) right there.!!

unraveled · Answer

D has two things that makes is wrong.
1. What role knowing of climate then and now plays to help us know which theory is acceptable based on its completeness? At the most, there is no relation from the way D is written or it gives information.
2. If the climate there was as dry when the dinosaurs lived as it is now both the theories are false. The dinosaurs could have vanished because of some other reason OR a far sighted, unimaginable possibility would have been that dinosaurs were still living. In any case the asteroid-impact theory is not at all a cause for extinction.

BinodBhai · Answer

**Understanding the Core Argument:**

* **Asteroid Theory:** A single, catastrophic asteroid impact caused the extinction of dinosaurs and other species.
 * **Evidence:** Extra-terrestrial element in a worldwide dust layer (the K-Pg boundary), found at the time of extinction.
* **Volcanic Theory (Competing):** Massive volcanic activity caused extinctions by cooling the planet (dust in atmosphere).
 * **Evidence:** Extensive volcanic flows in India (Deccan Traps) at the same time period.

The question asks what most strongly indicates that the asteroid-impact theory is **at least incomplete, if not false.** This means we are looking for evidence that suggests the asteroid impact wasn't the *sole* cause, or perhaps not even the primary cause.

**Analyzing Option (E):**

**(E) The fossil record in Montana from below the layer of extraterrestrial dust shows a diminution over time in dinosaur species from 35 to 13, and dinosaur teeth found above the dust layer show a diminution in species from 13 to 5.**

Let's dissect this:

1. **"Below the layer of extraterrestrial dust shows a diminution over time in dinosaur species from 35 to 13..."**:
 * This is the crucial part. The "layer of extraterrestrial dust" is the hallmark of the asteroid impact.
 * If dinosaur species were *already declining* (from 35 to 13) *before* the asteroid impact, it strongly suggests that something *else* was already stressing the dinosaur populations.
 * This pre-impact decline means the asteroid impact, even if it occurred, was hitting an already vulnerable and diminishing population. It wasn't a sudden, unprovoked extermination of a thriving group. This makes the asteroid impact theory, as a *sole* explanation, incomplete.

2. **"...and dinosaur teeth found above the dust layer show a diminution in species from 13 to 5."**:
 * This part reinforces the idea of a continued decline *even after* the asteroid event. While the asteroid event might have caused a significant drop (from 13 to 5 is a rapid decline), the initial decline (35 to 13) happened *before* it. This suggests a multi-stage or ongoing process of extinction, not just a single catastrophic event.

**Why (E) weakens the asteroid theory (or makes it incomplete):**

The asteroid theory posits a sudden, catastrophic event as the *primary* or *sole* cause of the extinction. If dinosaurs were already in a long-term decline *before* the asteroid hit, then:

* The asteroid might have delivered the final blow, but it wasn't acting on a robust, healthy population.
* Other factors (like the volcanic activity, or something else entirely) were likely already at play, weakening the dinosaur populations over a prolonged period.
* Therefore, the asteroid impact alone cannot fully explain the overall pattern of dinosaur extinction; it makes the theory *incomplete* by not accounting for the pre-existing decline.

**In summary, (E) is correct because it introduces evidence of a significant decline in dinosaur species *before* the asteroid impact event, thereby demonstrating that the asteroid impact, if it occurred, was likely not the sole or initiating cause of the dinosaur extinction, thus making the asteroid-impact theory at least incomplete.**

I had a hard time understanding this.. asked AI. Thanks to AI for this wonderful response.

A favored theory to explain the extinction of dinosaurs, together with

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