Biologist: Scientists have discovered fossilized bacteria in rocks 3.5 billion years old. The fossils indicate that t...

Mehran on November 12, 2017

Hi there, thanks for your post. This is an Argument Structure question. Let's start with an analysis of the argument in the stimulus:
P: Scientists have discovered fossilized bacteria in rocks 3.5 billion years old.
P: The fossils indicate that these bacteria were quite complex and so
SC: must have already had a long evolutionary history when fossilized 3.5 billion years ago.
P: However, Earth is only 4.6 billion years old, so
SC: the first life on Earth must have appeared soon after the planet's formation, when conditions were extremely harsh.
C: This suggests that life may be able to arise under many difficult conditions throughout the universe.

As you can see, the stimulus has a series of premises, including two subsidiary conclusions (SCs). A subsidiary conclusion is a statement that is supported by a premise, but which itself (in turn) acts as support for the ultimate conclusion.

That is why answer choice (C) is correct. Hope this helps!

hadeclat on November 12, 2017

Thanks!

rebut on August 4, 2020

Hi! Do all subconclusions need a premise? Or can they stand alone?

Thank you.

shunhe on August 4, 2020

Hi @rebut,

Thanks for the question! By definition, sub conclusions must have premises that support them. Otherwise, if they were just asserted without any support, they’d just be premises! That’s what differentiates sub conclusions and premises. While premises are unsupported statements that support conclusions, intermediate conclusions (or sub conclusions) are statements that are supported by other premises, but go on to support the main conclusion. So they cannot stand alone, and need premises.

Hope this helps! Feel free to ask any other questions that you might have.