Small enclosures

These are from Cowassock woods. I believe these to be among the oldest structures we can detect by eye. Thought I would show some examples:

I think these are pretty much the same as what we see at places between Horse Hill and Blood Rd in Groton, at places in Acton off Briar Hill Rd, at Scott Reservoir in Fitchburg. They are always barely above ground, and big enough for one person. Talk about speculation, here comes one: if it is true that these are of a kind with larger and fresher looking "rock piles with hollow" then the trend is from small single person burials to larger single or multi- person burials.