Hmmm. Not sure about the corrals idea but the people that built them left very, very few traces of general habitation. Most of what they constructed was temporary, wooden and perhaps mud built houses. The only major surviving indicators are things they wanted to outlive them, perhaps for their idea of eternity. Animal pens? Its not a practical use of scant energy and labour resources to drag massive rocks across the countryside to hold in cattle when wooden stakeposts would have done the job for a fraction of the labour cost.

A task like building a circle requires huge motivation, determination and perseverence. To my mind the only motivations strong enough, even today, to make impractical, labour intensive, lasting and obviously symbolic creations are creative expression, superstitious worship/fear or duress.

Where evidence does show agricultural use of land, like the Ceide Fields from 3,000bce http://www.rootsweb.com/~fianna/history/prehist1.html show the most practical way in which land was used: angular, rectangular and squared fields which are the most efficient use of space (which had to be cleared from forest). The walls are built of smaller stones that a man or two could carry so it was more efficient to build rather than tie up eight or more men moving one large rock to fill a fraction of the space a dry wall could fill.

I think its only right to wonder what uses circles had, but look at stone rows, portal tombs, standing stones, passage tombs; when they went to all that effort and in every case it was not a practical venture, it took a lot of back breaking work and that says to me the motivation was not to create something that was practical when a more practical solution using wood/branches/mud/small stones could use their valuable resources much more efficiently. This mysterious motivation and the psychological picture it paints of what went on in these peoples heads is what fascinates me but I'm very open to the idea they were day to day objects. It just doesn't make sense to me.