I would suggest using economies of scale as a factor in explaining consolidation. It is certainly a factor in the developed world. And it has been used as a theoretical cost to fragmentation in the developing world see: Guang H. Wan & Enjiang Cheng .2001, Applied Economics, 33:2, 183-194.

But I think the forces causing fragmentation are less about economics (there could be advantages to fragmentation if there are diseconomies of scale or very cheap labor). I think the answer is more along the lines of egalitarian transfers of estates. Farmers pass a small part of their land base to each child to be fair to the children. I know it was especially problematic in Greece and there was some work on the impacts.