Oily hair and growth

Hi hv, sorry for all the hair questions, it just occured to me, all the wild animals don't have access to shampoo, so how come their hair isn't overflowing with oil like our hair would do if we didn't shampoo it all the time, I mean, they can just bathe in water and they look great, how come we can't do that, what makes hair so oily? If we didn't use shampoo at all would our hair stop being so oily and be okay with just water-rinsing?

EDIT- I found this, which says our hair produces way too much oil because we keep shampooing our hair, makes sense

http://www.instructables.com/id/How-to-Go-No-Poo/


so they advocate not using shampoo, pretty hard idea to compensate, how am I going to get nasty things out -.-
but more importantly, they reccomend baking soda to remove grease, which I dont like because it would remove the acid mantle, so two questions hv,

does hot wait remove the acid mantle?
is there any acidic 'shampoo' that would remove excess oil while one transitions to a no-shampoo lifestyle, so you dont have to use baking soda, then acidic product, etc?