I guess your ;) was that the trees post date the stone walls by how many millenia. (??)
Yes!
The link in post 37 is interesting. Shows a map of the wall with respect to the topography of the hill. Those dips in the wall could have been used to collect water perhaps. Interesting comments about the wall relating to astronomy, and other items from that area and time indicate they were somewhat interested in it.
Or - it was just where the rocks ended up after clearing their planting area. (Perhaps it is the trail from a very large mole!?)