The claim the question refers to is that the widespread assumption that cooking could not have impacted biological evolution because its practice is too recent appears to be wrong. The question asks us to identify a statement that would strengthen the claim.
(B) is correct because it demonstrates that evolutionary biological adaptations are possible over a relatively short period of time, 5000 years or less, thereby further refuting the assumption that cooking is "too recent" for it to have any impact on biological evolution.
Let me know if this makes sense and if you have any further questions.