Question

human cannot digest cellulose like grass eating animals

Answer 1

Caecum is the site of digestion of cellulose. Man is omnivorous, it's food dose not contain much cellulose. Hence Caecum is nonfunctional and poorly developed in human

Answer 2

Animals such as cows have anaerobic bacteria in their digestive tracts which digest cellulose.Humans are unable to do so because the appropriate enzymes to breakdown the beta acetal linkages are lacking.