Archaeologists are later (second industrial civic along the top). You need Mercantilism, Colonialism and then Natural History to get the actual Archaeologist. If you want the boosts, you need to get a great merchant, astronomy tech and build an archaeological museum.
And you must have an achaeological museum in to recruit an archaeologist (and can only do it in that city, as they're tied directly to the specific museum). They get three uses, and then the museum is filled. If you want more, build more theatre districts and more archaeological museums.