QUESTION TEXT: Geologist: The dominant view that petroleum…
QUESTION TYPE: Weaken
CONCLUSION: It is wrong to say that petroleum formed from lifeless deep carbon deposits.
REASONING: Petroleum has biomarkers, and biomarkers come from living things or from things that were once alive.
ANALYSIS: This argument has a missing premise. The geologist is trying to prove that the petroleum formed from living things in the past.
The presence of biomarkers isn’t definitive proof, because the biomarkers could come from things that are alive now, or were recently. The geologist assumes, without evidence, that the biomarkers must have come from long dead life forms.
- The author didn’t say that all fossils have biomarkers. It’s possible that some fossils lost their biomarkers due to the effects of time.
The geologist’s claim is that if you find a biomarker, then there must have been life. But something could have been alive even if we can’t currently find bi0markers.
- The author didn’t say when petroleum formed. Both petroleum and living organisms might have formed long after the earth’s formation.
The only reference to the earth’s formation is that the carbon deposits formed not long after the earth did. But that doesn’t mean that petroleum formed soon after the earth did. Petroleum could have started forming later, when life existed.
- The argument didn’t say how long petroleum takes to form. Several million years could be fine.
- CORRECT. If bacteria live deep in the crust, then they could live near petroleum. Perhaps the bacteria leave biomarkers in the petroleum. Therefore the biomarkers are not a sign the petroleum originally formed from life. They are merely a sign that bacteria are currently present.
- The geologist is defending the dominant view that petroleum formed from fossilized plants and animals. So knowing that at least some petroleum deposits formed from plants strengthens the geologist’s argument.
Free Logical Reasoning lesson
Get a free sample of the Logical Reasoning Mastery Seminar. Learn tips for solving LR questions