Why can’t humans eat grass?


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There are several things which differentiate humans from the other animals present in the world – in a way, we are more evolved than they are, making us “superior”. However, there are a few things humans fall short of. Given the resources at our disposal, an average human would possess the necessities of life. These necessities have aided us in forming better lives for us, but these have set us apart from other animals more than evolution has intended for.

Wild animals inhabit forests and can nourish themselves with whatever is available, but a human in this situation would probably not be able to survive. We cannot eat raw food, which drove our ancestors to use fire as more than a defense mechanism. It is rather puzzling to understand why this is so – all the other animals, domesticated or otherwise, have looked to raw food to fill their stomachs. Of these, the most popular one is GRASS.

Every animal, directly or indirectly, is dependent on this commodity called grass to nourish themselves. The FOOD CHAIN ascertains this as the distinctions have been made.

  1. HERBIVORES are animals who only consume grass and related food – e.g. A cow.
  2. OMNIVORES are animals who are dependent on meat and grass – e.g. A bear.
  3. CARNIVORES are animals who prefer only meat – e.g. A lion.
cycle of life

Humans are biologically omnivores, but with the arrival of civilization, nutrition has become a personal preference instead of a biological feature. Vegetarian or otherwise, humans cannot consume grass, and this is because our bodies simply cannot digest it. The digestion process is one of the marvelous functions our bodies can perform, and they heavily rely on the presence of ENZYMES.

Enzymes are protein conjugates that behave like catalysts in our bodies. To deduce their importance, this situation is given – If digestion did not involve enzymes, breakdown of one meal would take a lifetime. Each enzyme has a specific function; there are enzymes that overlook the breakdown of proteins and some which oversee the breakdown of carbohydrates. The specificity of enzymes goes beyond the surface level and the world of enzymes is enormous. As a short answer to “Why can’t humans eat grass?”, humans cannot eat grass as they do not possess the enzymes required to digest it.


Which enzymes are involved in the digestion of grass?

The grass is a plant. Plant cells have CELLULOSE – a hard and stiff carbohydrate that helps a plant cell maintain its structure. Hence, a large part of the grass is cellulose, which cannot be digested by humans. Herbivores like cows have a different stomach than humans do – whereas human stomachs have just one stomach, cows have a four-chambered stomach. Their stomachs also possess an enzyme called CELLULASE, which is specific to breaking down cellulose into its constituting GLUCOSE molecules. The four-chambered stomachs of cows have specialized functions to break down cellulose (using cellulose) and then absorb any nutrients from grass. This trait is inherently absent in humans.

green plant

Do humans need to consume grass?

The answer to this is no because of various reasons. The predominant reason for humans not needing grass to nourish themselves is that we have a large variety of food to choose from – such as vegetables, fruits, and meats. Most animals are unable to access such a variety, much less choose what to eat. Herbivores find it convenient to wander to grassland to graze. The other reason for not having to consume grass is because it has little to no nutritional value – or little to no nutritional value that humans can harness from it. Rather, the heavy amounts of silica in the grass can result in abrasion of tooth enamel, thus concurring us more harm than benefit.


Were humans ever able to eat grass?

While it is hypothesized that Homo sapiens have never been able to eat grass, but older ‘versions’ of humans would have been able to. Palaeontological evidence indicates that the hominid Australopithecus bahrelghazali would have been able to chew and digest grass as well due to the structure of their teeth. A popular Australopithecus is a skeleton called Lucy. It is believed that since humans started using fire to cook their food instead of consuming raw food, their ability to digest raw food became vestigial, which was lost over time.

old human teeth

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