I always wondered... how do the Villages keep their bloodlines so 'pure'? For example, the Uchiha clan is shown to have at least a dozen members, probably somewhere close or in excess of a hundred. Now, given that it is confirmed that the Uchiha inherited the Sage's Eyes from<em>one</em>ancestor... repeated marrying non-Uchiha would eventually dilute the bloodline to a sliver.<br/><br/>Are they like dog breeds, where constant inbreeding produces the desired effects?