Necessary AssumptionDiff: Medium
Logic Breakdown
Passage Summary: We found a lizard fossil that is older than any anthracosaur fossil ever discovered, so the argument concludes lizards couldn't have come from that group.
Conclusion: Lizards could not have evolved from the group of amphibians known as anthracosaurs.
Reasoning: The oldest known anthracosaur fossils are 300 million years old, but a lizard fossil has been found that is 340 million years old, and a species cannot predate its ancestors.
Analysis: The argument relies on a significant 'Gap' between the fossil record and biological reality. It assumes that because we haven't found an anthracosaur fossil older than 300 million years, anthracosaurs simply did not exist before that time. For the conclusion to hold, the argument *needs* it to be true that there are no undiscovered anthracosaur fossils that predate the 340-million-year-old lizard. Look for an answer that addresses the possibility of anthracosaurs existing earlier than the current fossil evidence suggests.
Conclusion: Lizards could not have evolved from the group of amphibians known as anthracosaurs.
Reasoning: The oldest known anthracosaur fossils are 300 million years old, but a lizard fossil has been found that is 340 million years old, and a species cannot predate its ancestors.
Analysis: The argument relies on a significant 'Gap' between the fossil record and biological reality. It assumes that because we haven't found an anthracosaur fossil older than 300 million years, anthracosaurs simply did not exist before that time. For the conclusion to hold, the argument *needs* it to be true that there are no undiscovered anthracosaur fossils that predate the 340-million-year-old lizard. Look for an answer that addresses the possibility of anthracosaurs existing earlier than the current fossil evidence suggests.
Passage Stimulus
Passage Redacted
Unlock Full Passage12.An assumption made in the argument is that there are no
Correct Answer
A
A states there are no unknown anthracosaur fossils older than 340 million years. Negation test: suppose there are anthracosaurs older than 340 million years (we just haven’t found the fossils yet). Then anthracosaurs could predate lizards, and lizards might have evolved from them. That collapses the argument, so A is necessary.
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