why do humans need to eat many different kind of foods to get their vitamins etc but large animals like cows only need grass to survive?
In: Biology
We don’t. We just like to. Humans can survive on very simple diets. Gauchos would live entirely on beef for example.
Because their digestive system is centered around their natural diet. People would naturally eat all different kinds of things, but cows would only normally eat grass. I’m a horse owner, and sometimes I find that my horses will be eating dirt. This is because they can tell they have mineral deficiency so they take it into their own hands and eat dirt to get those minerals. It’s always a certain time of the year when my horses are coming in from pasture with muddy mouths, so then I’ll go buy a mineral block for them to lick or I’ll buy them some loose minerals to sprinkle in their feed. I like to leave blocks, because then they can decide when they need it and when they don’t because too much mineral could cause issues and it’s more natural for them that way. I’ve seen people with cows leave troughs of loose mineral in the pastures and the cows take a few mouthfuls when they feel like they need it. Digestive systems in large animals are so so different from those of humans
In short… because as humans got smarter, our diets became better and more diverse because we had the anatomy and ability to get better food. Therefore our digestive system became much more streamlined and simple. That means it doesn’t pull as many nutrients from each meal, cuz we have trained our guts that it doesn’t need to.
Extra details… The human brain has tripled in size over the last 3 million years. This is because humans began to eat a wider range of food, and began to cook our food. This meant the digestive system needed to work way less than it did before. Less energy to the gut, meant more energy to the brain.
Better food = bigger brain.
You can see this in the animal kingdom, as animals with very simple, nutrient deficient diets, tend to have very small brains. The body has to spend so much energy on the digestive system, that little goes to the brain, and evolution keeps the brain small.
TLDR; We need better food cuz we eat better food, and we made our body accept that.
Others have explained it well, but another fact about many animals that we think of as herbivores(cows, deer, squirrels) will commonly eat meat if it’s available! Cows and deer have both been seen munching on baby birds in low nests, as well as chewing on bones from carcasses
Fun fact: We actually still have most of the genes required to synthesize vitamins, such as the gene to synthesize vitamin C which dogs and cats possess, but it is deactivated.
When we started living arboreal lifestyles and consuming a lot of fruit, it was no longer evolutionary preferential to synthesize our own vitamin C- it takes much less energy to absorb it from food, where the plants have already expended the energy to synthesize it- and therefore the gene has gradually grown redundant in chimps and eventually humans.
The same has occurred for many other aspects of our genes. Any expense of energy which can be avoided is generally selected against, because individuals who could survive longer with less food were more likely to survive periods of scarcity and thus produce offspring.
Because it is the most efficient. We can get all the nutrients we need in about an hour over all and spend the rest of the time doing stuff.
Carnivores spend 80% of their day sleeping, and herbivores spend 80% of their day eating. We spend 30% of our day sleeping and <10% eating. It’s the best of both worlds.
At least one thing is that we can’t make vitamin C ourselves, which is a negative mutation we have compared to other animals.
I’m not going to try to explain why humans and animals eat different foods because I don’t know enough about it myself.
What I can tell you is that humans *can* survive on extremely limited diets. They just won’t be as healthy as someone who eats different kinds of foods.
1. Different animal’s digestive systems work very differently
2. You could survive on only potatoes, you would just be far less healthy and have a reduced lifespan, like many animals in the wild vs those in captivity.
Part of it is they’re bulk feeders. Cows will eat 20+ pounds of food a day, up to nearly 40 lbs for meat cows being fed for fast weight gain. They spend a huge portion of their waking hours just eating, with an otherwise sedentary life.
From this enormous food intake they can extract a decent quantity of nutrients that are relatively scarce in their diet. For more complex nutrients they basically carry around a biological factory in their gut to process the vegetable matter into all the proteins they need from their diet.
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