The statement about ice-age nomads’ portrayal is not a premise, because it doesn’t support the argument’s conclusion. The claim that many people think ice-age nomads were big-game hunters gives us no reason to believe that nomads mostly got food from other sources.

The statement that ice-age nomads are commonly portrayed as big-game hunters is unrelated to the argument’s premises, and definitely doesn’t clarify them. The premises are about how ice-age nomads actually lived, not about their popular depiction.

Firstly, the argument doesn’t present an opposing theory, just a common misconception and an explanation of why it’s wrong—so this can’t be true. Secondly, the anthropologist doesn’t use this statement to make any kind of point; it’s not a premise of any kind.

The statement about common depictions of ice-age nomads isn’t the conclusion because nothing else in the argument supports it. The anthropologist’s conclusion, supported by factual premises, is that ice-age nomads mostly got their food from plants and small animals.

This is exactly the role played by the claim that ice-age nomads are often portrayed as big-game hunters. The anthropologist’s argument is focused on proving why that portrayal is wrong, by showing that ice-age nomads mostly ate plants and small animals.