“What is more important is that in order for a custom or innovation to be preserved, there were two distinct prerequisites. Firstly, there must have existed some conditions that made possible the preservation through generations of certain practices whose benefits were not necessarily understood or appreciated. Secondly, there must have been the acquisition of distinct advantages by those groups that kept to such customs, thereby enabling them to expand more rapidly than others and ultimately to supersede (or absorb) those not possessing similar customs.”