It is animal preservation. When animals are threatened they need all their strength to survive.

The strong to fight, the fleet of foot to run. They will excrete and or vomit to enable the blood circulation to build up the muscles quickly to prepare them for survival.

Through generations we have been [Potty] trained and thus the humans just fart. Some can of course,

in severe cases, fill one`s trousers. No i am not joking it is true.