#23 - Geologist: The dominant view that petroleum formed

[AthenaDalton]

Hi dpbk,

I think you're actually reading the stimulus correctly -- your explanation was on-point!

I suspect that your confusion stems from understanding what answer choice (D) is saying. Answer choice (D) tells us that certain types of bacteria can live very deep underground, presumably within the carbon deposits that have existed since the formation of the earth. This answer choice isn't saying that the carbon deposits are actually made up of bacteria -- just that bacteria happen to be living deep inside the earth where this carbon is found. Does that distinction make sense?

Since the geologist is arguing that the existence of biomarkers = carbon formed from fossilized plants and animals, any fact that could explain the existence of biomarkers apart from the fossilized plant/animal theory would weaken his argument.

Thanks for your question, and best of luck studying!

Athena Dalton

[nmgee]

Athena's explanation makes sense to me, but I still have trouble with this question. My understanding is:
Dominant view: petroleum formed from plant/animal remains
Challenger view: petroleum formed "not from living material" but from C deposits
Geologist's view: challengers must be incorrect because biomarkers in petroleum indicate presence of a living org.

So, I understand why (D) could be correct if the challenger's view was "petroleum was not formed from plant/animal remains" because bacteria is neither plant nor animal. But the possibility that the biomarkers formed from bacteria would not refute the "challenger view" because that view is that petroleum formed "not from living material" and bacteria is living material.

So if we're meant to weaken the geologist's view (that the challenger's view is refuted by biomarker evidence), the only way I see (D) being correct is if the challenger's view stated "not from plant/animal material" rather than "not from living material". Can anyone explain this discrepancy I see?

Thanks in advance for your help.

[BostonLawGuy]

To me this question is very questionable. First it assumes that we somehow know that bacteria and organic material are mutually exclusive. To the contrary, after many years of biology courses and working in the field, I know that bacteria and organic material are connected.

The corrected answer seems to assume that because there are bacteria in the earth's crust, biomarkers in petroleum can't be or are less likely to be from organic material.

It appears they are going after weakening by "alternate cause." Not sure I see how it logically follows. Or, maybe I am missing something?

[Dave Killoran]

This is a very difficult question, with only around 30% of test takers correctly selecting (D), and nearly the same percentage selecting (A). And, of course, anytime you get into the questions in the late teens/early twenties in an LR section you are more likely to run into extremely tough questions such as this one.

Whenever analyzing these answers, the paramount rule is: what does LSAC think and why do they say this is correct? As I've said elsewhere, this is their world, and our job is to figure out why they think each answer is correct or incorrect. So, with that in mind, let's take a look at answer choices (A) and (D).

Let's start with what the challenging scientists think. Their view is that petroleum formed from deep carbon deposits, and it did not form from living material. Note that I emphasized formed from because this is the broad causal element in what lead to petroleum. The geologist responds that hey, we found biomarkers, so those challengers are dead wrong about it being carbon. Note that the strength of this conclusion plays a role in answer choice (D) being correct.

From a prephrasing standpoint, we want an answer that somehow undermines the biomarker fact/explanation, and hopefully also supports carbon in some way or at least allows for it to exist as an explanation.

Answer choice (A): Although this answer helpfully mentions biomarkers, it turns out to be a trap. This answer talks about the lack of biomarkers in some fossils (not all) whereas in this instance the geologist is using the presence of biomarkers to make a point. The geologist would likely try to say that a lack of biomarkers elsewhere is meaningless but the presence of biomarkers in petroleum proves it's not carbon. To use a really rough analogy, it's as if someone claimed that the presence of apples in a store means it is a grocery store, and then someone else tried to undermine it by saying that some stores don't have apples. That type of response typically garners a "well, there are apples in that store, so it's a grocery store" kind of reply, or, as in this case, "we have biomarkers so it was plants and animals that lead to the petroleum."

Answer choice (D): As we know, this is the correct answer, and it's a tricky one. The geologist has made an argument that because biomarkers are present, it's not carbon deposits. But if (D) is true, we could have strains of bacteria way down in the crust that leave biomarkers within the carbon (and, as LSAC expect us to know, bacteria are small, and not really the same as "plants and animals"). So, this allows us to explain presence of the biomarkers while at the same time still allowing for carbon deposits to be what petroleum was "formed from." Does this kill the geologist's argument entirely? No, but the geologist made a very strong statement ("their theory is refuted") that is not 100% provable if (D) is true.

One helpful way of thinking about this answer is to consider that the geologist seems to think that the presence of biomarkers automatically means that plants and animals were present (and were thus the cause of petroleum), whereas (D) suggests that the presence of biomarkers doesn't have to mean that plants and animals were present. Answer choice (D), in other words, attacks this causal assumption made by the geologist.

Again, this is a very difficult question overall, and the correct answer feels counterintuitive. But the key when analyzing the problem is to consider why LSAC would say (D) is correct. They always have their reasons!

[T.B.Justin]

Bacteria are classified as prokaryotes for anyone that cares to know!

If I knew that bacteria are neither plants nor animals this would have altered my perspective of this question entirely!

[gwlsathelp]

There is a lot more to this question than meets the eye. At the outset, the geologist is just explaining a situation: there's the dominant view and it's being challenged, the challenge does not hold up because of evidence. In order to weaken the geologist's argument (show that the opposing viewpoint could work) we either weaken the dominant view, strengthen the opposing view, or both.

What gets me is that there is already a lot of talk about living organisms in the stimulus. To me, this added to my confusion when I saw answer choice D. "Not from living material" refers to "the fossilized remains of plants and animals", while the definition of biomarkers includes both present and past indications of living organisms. The presence of biomarkers, as defined, does not indicate whether or not the organism is currently alive or dead/fossilized. The geologist assumes that the biomarkers appear because of the fossilized organisms. Answer choice D offers a different explanation to why biomarkers appeared (bacteria chillin' in petroleum, livin' their life not fossilized), thus regardless of whether or not the petroleum was formed from carbon deposits or from fossilized organisms, the presence of biomarkers/currently living organisms makes it possible for the opposing view to be correct.

Fun article from the NewScientist on the actual phenomenon that this question is based around. Even without this knowledge, you are supposed to see that answer choice D is the correct answer as it's an alternate explanation.


In any case, writing these explanations out helps me to better understand the reasoning behind the LSAT. Thank you for coming to my Ted Talk.

[TheySeeMeRolin]

This question is still not sitting right with me either. I actually ruled out D as a nonsense answer. The presence of “bacteria…deep inside the earth’s crust” seemed irrelevant to “deep carbon deposits dating from the formation of the earth.” We know the bacteria and the carbon deposits have both been described as “deep,” but how can we know they are close in proximity (such that the presence of bacteria resulted in the biomarkers in petroleum theoretically formed from carbon deposits)?

Not sure if there are any tips you can give me on how to more easily arrive at this conclusion, appreciate it if you do. Thanks!

[Rachael Wilkenfeld]

Heya Rolin,

The key thing to notice is that bacteria are organic. We can match up the deep petroleum in the Earth's crust with the bacteria in the Earth's crust to realize both things are talking about the same area in the Earth. Even though we don't know they are anywhere near one another, the fact that the bacteria are thriving is enough to say that it COULD be close to the petroleum. Remember our answer choice doesn't need to disprove the stimulus, only make it less likely. The stimulus tells us that the biomarkers indicate either past OR present organic material. The assumption they want you to make is that it has to be from the past. But if it's the case that in the present there are numerous organic lifeforms in the same area the petroleum, it would weaken the conclusion that the biomarkers indicate the petroleum was from ancient fossils.

Hope that helps!

[goingslow]

Hi there!

I read all the previous explanations but still have a lingering question. I am not sure which one (D) is trying to do. Is it (1) suggesting that bacteria (a living organism) account for the biomarkers discovered in petroleum, thus weakening the claim that biomarkers necessarily indicate fossilized remains of plants and animals, OR (2) advocating for the hypothesis that the presence of biomarkers, which are bacteria that thrive deep inside the earth’s crust in this case, indicates deep carbon deposits?

For (2), I’m hard pressed to convince myself that those carbon deposits are found deep in the earth’s crust, which is where the bacteria are.

Also, for answer choice (E), I thought it reconciles the upstart scientists’ theory (that petroleum forms from carbon deposits) with the presence of biomarkers? If some carbon deposits were formed from the fossilized remains of plants, and fossilized remains of plants contain biomarkers, then carbon deposits would have biomarkers too.

Any light you can shed on these questions will be greatly appreciated!

[supjeremyklein]

some people think oil doesn't form from living stuff in the crust, but from carbon stuff in the crust
but since oil has biomarkers that exist in living stuff, the carbon idea is questionable

(d) living stuff like bacteria thrive in the crust

if bacteria thrives in the crust, and bacteria is something that would have a biomarker, then how would we know for sure that the biomarkers popping up in our oil is indicative of the living stuff that made the oil?

the oil could've been made from the carbon stuff, but mingled with the bacteria thriving in the crust

FOR POSTER ABOVE
(e) carbon stuff can form from fossils (which would have biomarkers) but that doesn't mean that the carbon stuff now inherits its biomarkers. rain forms from the sea (the sea has salt) but that doesn't mean rain has salt in it!

so (e) is vague, and it's also sort of irrelevant to the argument. (e) talks about some relationship between carbon stuff and how it could form from fossils, the argument is mainly about oil and its origin-formation