SAT Writing ambiguous pronoun error?

Can anyone please explain why this sentence is incorrect?

When Russell Wallace and Darwin independently proposed similar theories, Darwin had already accumulated extensive evidence with which to support his ideas.

I thought the error was at with which because it seems wordy; to me, evidence to support an idea sounds better and less wordy than evidence with which to support an idea. But the error occurs at his, and it's an ambiguous pronoun error.

Thank you!


The argument made in this example paper is that his could perhaps apply to Darwin, or perhaps to Russell Wallace.

Personally, I think this is nonsense, it's perfectly clear that his refers:

  1. To the only male person previously referred to on their own, viz. Darwin.
  2. To the male person most recently referred to, viz. Darwin.
  3. To the only male person referred to in this clause, viz. Darwin.

I also don't see anything wrong with any of the rest of it. The problem lies in the examiner's reading comprehension, not the sentence. I'm glad I never had to do SATs.


In this sentence, "his" is unclear as to whether it is referring to Darwin or Russell Wallace. We know both Wallace and Darwin proposed similar theories, and we know Darwin had accumulated extensive supporting evidence, but we don't know exactly whose theory the evidence supports (it could be Darwin or it could be Russell Wallace). The sentence should be rephrased or a new word should be chosen to clarify.