Can someone explain why animals lick themselves and their young clean? What could possibly be harmful about the dirt on their thick virtually inpenetrableskin that would not do even more harm in the sensitive, porous environment of the gut, wher it will surley end up if licked off?

It's to do with hygiene and keeping themselves clean though animals can get ill because of stuff they may have picked up from doing this. It's also to do with establishing heirarchy or being social.