I think whether or not a site will have a privy of some kind is a
function of familiarity with and acceptance of hygiene and germ theory;
shared ideas about privacy, cleanliness, odor tolerance, etc; and how densely
occupied the site is.  Obviously also a topic where we need to be careful not
to insert our own sensibilities.
     Visitors asked about the presence/absence of privies here on this
plantation site very frequently.  We usually give them some version of the
above, and explain that probably for the enslaved African-Americans it was a
matter of slop buckets in the corner (although a few ceramic chamber pots
have come to light) or a designated spot in the yard or the nearest clump of
trees.
     Nothing like a little talk about bodily functions to wake up the list,
eh?
            Yrs,
              Larry McKee