I've often wondered about vocabulary in the neolithic. How many words did our ancestors have, given the limited nature of their culture?

Here's a tract from Wikipedia on modern vocabulary: Native speakers' vocabularies vary widely within a language, and are especially dependent on the level of the speaker's education. A 1995 study shows that junior-high students would be able to recognize the meanings of about 10,000-12,000 words, while for college students this number grows up to about 12,000-17,000 and for elderly adults up to about 17,000-21,000 or more.