Question

human beings do not have a chambered stomach like cows. why do we lack the process of rumination?explain

Answer 1

Cows and many other other animals such as Gazelles, have a chambered stomach, this evolutionary trait is seen in such animals due to their distinct diet. Such animals eat leaves for their nutrition, plant matter such as leaves and grass are harder to digest than meat and don't provide instant energy. Hence, a chambered stomach provides an edge over a non chambered stomach by increasing the length of the digestive system and help in digestion. 

Humans on the other hand, have a non chambered stomach due to the food they eat, humans eat far more easily digest-able food, which is usually cooked. Thus they don't need a chambered stomach.

Rumination is also a process associated with chambered stomach, in which half digested food is regurgitated and is chewed over again in order to ease the process of digestion by ruminants such as cows, who always have a chambered stomach. This is also an evolutionary trait based on cows' diet, which needs a chambered stomach.

Again, humans can't do the same thanks to the absence of a chambered stomach and no need for doing the same.