Human beings do not have a chambered-stomach like cows. Why do we lack the process of rumination, explain
ruminants like cows and giraffes eat exclusively leaves, which are difficult to digest. The four chambered stomach provides a long digestive cycle, which they need to get enough energy. Humans and most other animals eat foods with more easily available energy, so a shorter digestive tract serves us just fine and there was no selective advantage in having a more complex digestive system.