There is no such thing as a stupid question. :)
Sunken Civ is on the money as always, But one detail I would like to add is soil layers. Digs are done inch by inch, one layer of soil at a time as they go deeper. And over time soil was deposited over these sites in layers. So if they find a lithic at a certain depth and layer of soil, and they also find organic materials that can be dated in that same layer, then they are almost certainly the same age as long as the soil has not somehow been disturbed.
One of the reasons these discoveries come so slow and few in between is because while many lithics might be found at a site, The chances of finding corresponding organic material to date a layer and lithics also in that same layer are actually pretty rare. Animal bones, a cooking fire hearth, lithics, and a human burial together are the jack pot of course.
So while some lithics can be dated from a particular style of knapping because they are the same or similar to other known previously dated lithic cultures, 999 out of a 1000 date estimates for digs are always discredited until organics are also found and carbon dated.
At this site they have found western stemmed style lithic points very similar to the ancient Jomon stemmed points found in Japan. This is what has them looking in that direction as the source of the occupants at this site. A burial would be golden to find, then DNA could possibly be chased down and traced to origin.
That's right. I know the guy who did most of the lithic analysis on this dig.