I think we humans begin the construction of our "walls" early in life... say around the 3rd grade or so. Why is this? It is for protection against the "what is mine is mine and what is yours is also mine mentality." We begin early construction of these walls not only for protection, but also for our need to fit in with the crowd. As we age we identify with certain groups. We talk and dress like everyone else in the group. Once we reach adulthood, our armor changes from jeans and a tee shirt to a suit and tie. But those walls are stronger and more complicated than ever.