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Are Humans Meant To Eat Meat

In the UK, on average, humans consume 14% of their caloreis as meat, however as the vegan movement is gaining momentum, the question of whether or not humans are actually supposed to eat meat is currently being hotly debated across social media. Arguments on both sides compare humans to lions and animals that have evolved to eat plants, but can we determine the correct diet this way? To improve their chances of survival and maintain health and happiness it’s important for all animals to eat what they’re biologically designed to eat. But in a sea of second-hand knowledge, where ‘winning’ is often favoured over the truth, how do we answer the question, are humans meant to eat meat?

Animals in the wild use a primitive feedback mechanism to maintain homeostasis. This involves measuring everything from body temperature to levels of certain nutrients. Maintaining homeostasis requires that the body continuously monitors its internal conditions and keeps them within a normal range. When it comes to maintaining optimum nutrient levels, an animal needs to be able to identify the most biologically appropriate foods. It does this through signals that are sent back to the brain from its cells and organs after digesting a meal. Depending on its benefits, toxicity or lack of benefits to the body, the flavour of that food is recorded as either ‘good’ or ‘bad’. Biologically appropriate foods provide the strongest positive nutrient feedback, and the animal will seek out those foods again. An animal will also stop eating a particular food if it starts to receive negative feedback.

But how can feedback mechanisms in humans function properly in our unnatural, highly processed world? The flavour of many foods in modern society is unrecognisable from the original food source and we may even joke that ‘everything tastes like chicken’. Bacon flavoured crisps are often suitable for vegans, because the flavour of bacon has nothing to do with pork. Foods with a high amount of added sugar might make us feel good temporarily, but they aren’t nutritionally good for us. Likewise a food might be artificially designed to have a sweet taste, but provide very little energy or calorific benefit. Amidst the noise of our modern world, humans learn to overcome innate taste responses, and natures feedback mechanism is often, if not always, drowned out. Therefore how do we determine what the most biologically appropriate food is?

The common biological arguments for and against humans eating meat usually come down to their mouth parts and the anatomy of their digestive systems. So lets take a look.

  1. Teeth A commonly held view is that the presence of canine teeth indicates that the animals diet should be meat based. However the presence of canine teeth isnt enough by itself, to determine the diet an animal evolved to eat. Nearly every single animal on the planet posesses canine teeth, and it’s more useful to look at the entire dental anatomy in order to discover traits that may indicate biological diet. Carnivores have sharp pointy cheek teeth (carnissials), not just sharp pointy canines. They need these rows of sharp teeth to catch and tear apart prey. If an animal has either blunt or no canines, and big flat side and back teeth (premolars and molars) it’s evolved to eat predominantly plants.
  2. Jaw movement The jaw of a carnivore is a hinge joint that moves up and down, with little or no sideways movement. This is the correct tool required for tasks such as shearing, ripping, and tearing flesh and bone. It’s also the correct tool for gripping and holding moving prey without the risk of dislocation. It’s very stable and strong, lying on the same plane as the teeth. The jaw joint of herbivores on the other hand, is positioned above the level of the teeth, enabling a much bigger range of movement, designed for extensive chewing, crushing and grinding of grains and other high fibre foods. The jaws of humans, are very weak and dislocate easily when subjected to too much force.
  3. Drinking As juveniles and adults, carnivores drink water by scooping it up with their tongues curled backwards, which forces the water into a column and up into their mouths. Humans, like all herbivores, are incapable or creating this backwards tongue hook. Observe herbivores (like cows and horses) at a water trough, and you'll see that they drink by sucking or place some water in your cupped hands and observe your natural instincts. When we’re not using modern tools, humans also drink water by sucking it in using our lips and cheeks.
  4. Saliva The saliva of a carnivore doesn’t contain the digestive enzyme amylase and they swallow large chunks of prey whole, where the digestive process is started by their stomach. The burden of digesting carbohydrates is taken by the pancreas. For herbivores, digestion begins in the mouth. Food is chewed for a long time to mix it with saliva, in order to start breaking it down. The saliva contains carbohydrate digestive enzymes (amylase and lipase), which begin the process of digestion.
  5. Eating grass All taxonomy other than obligate carnivores, can eat grass and Humans are no exception. However just because we can do something, doesn’t mean that we should. Our stomachs and cecum are no longer used to coping with large amounts of grass, and both have shrunk over time, as an adaptation to the changes in our diet.

    Plant cells can be simplified into ‘cell wall’ and ‘cell contents’. The cell wall is made of cellulose and hemicellulose, which must be broken down before the easily digestible cell contents (like starch, protein, sugars, fats, and oils), can be used for animal nutrition. No animal, (either carnivore or herbivore) can digest cellulose, and the breaking down of plant cell walls must occur through a process of fermentation. Ruminants have a complex four-chambered stomach, which allows efficient fermentation and therefore energy extraction from plants. Ruminants can easily survive on just grass. Herbivores with monogastric digestion can ferment cellulose by way of symbiotic gut bacteria, however they are less efficient than ruminants. Monogastic cellulose fermentation can either take part in an enlarged stomach area (foregut) or large intestine and/or cecum (hingut).

    Obligate carnivores (like cats and dogs) can only consume very small quantities of grass without emesis. For this reason obligate carnivores (such as cats and dogs) may deliberately eat small amounts of grass in order to make themselves sick. Big cats use grass to purge indigestible parts like feathers, fur and bones, by eating large quantities of it. They can also use grass as a natural remedy that cleanse the intestines, by eating it in smaller amounts. The average lion still needs fibre in its diet, which is usually derived from plant matter. A small mouthful of grass per day can give them all the roughage or fiber they need to promote regular bowel movements and help food move through the digestive tract. Lions and other non herbivores may also seek out grass as a supplement for things that are in short supply in the wild. Grass often contains dried urine from other aninals, which is rich in minerals like folic acid.
  6. Stomach PH Given its primary role in digestion, stomach pH has been measured far fewer times than might be expected, for example no data on stomach pH exists for any hominoid other than humans, and very little for primates more generally. For a long time it was thought that there was a correlation between stomach PH and diet, largely due to the low stomach PH of some carnivores, and high stomach PH of some ruminants. However there seem to be a number of inconsistencies in the data. The stomach of a dog or wolf has a ph of around 4.5, whereas a rabbit has a gastric pH of 1.9, both of which contradict the theory that PH correlates with diet.

    A new theory exists that stomach PH is thought to be related primarily to pathogens. Scavengers, like buzzards, are thought to be most likely to encounter high levels of pathogens from eating rotting or petrifying flesh, whereas herbivores have the least exposure to possible pathogens and therefore least acidity. It’s interesting to note that humans, (uniquely among the primates), appear to have stomach pH values more akin to those of carrion feeders. It’s unclear exactly when such an acidic environment evolved, but it’s thought that natural selection may have played a role. Low ph in human stomachs is thought to be adaptive not biological, owing to the number of fecal-oral pathogens that have infected and killed humans in the past.

    It turns out though that our acidic stomachs are not very good for us. A large body of literature now suggests that adaptive lowering of our stomach PH has caused a variety of human medical problems, related to the loss of mutualistic gut microbes. Because we’ve got very acidic filters whenever we lose gut symbionts, (for example when we take antibiotics), the chance of re-colonising new symbionts are low.
  7. Liver Animal flesh, composed of the most highly complex type of protein that exists, requires vast amounts of uric acid to process. Uric acid is released into the system in amounts necessary to break proteins down into amino acids. Uric acid is a toxic substance responsible for the ageing process and must be flushed out and dealt with. That is one of the jobs of the liver. In relative terms, a carnivore's liver is a tool designed with the capacity to eliminate ten times as much uric acid as the liver of man or other plant eater.
  8. Appendages A predator has a gait, large paws and claws, which enable him to hunt, chase and trap his prey. These are tools meant to kill. Man's gait, as well as other herbivore's is designed only for mobility. Examine your hand, fingers and fingernails. Is this an apparatus properly designed for catching, trapping, killing and ripping apart cattle, hogs, chicken and fish? How does this work for picking fruit from trees or harvesting vegetables? The foods your hands were meant to gather are typically, high in water content, high in fibre (to sweep the wastes out of those intestines), and collectively contain every vitamin and mineral necessary to sustain human life.
  9. Cooling Mechanism Carnivores don't have sweat glands on their skin but herbivores do. Some herbivores lack sweat glands entirely, such as elephants, hippos, rhinos and pigs, however, no carnivores have sweat glands on their skin. Carnivores sweat through their tongues and cool themselves off by panting. Herbivores, like humans, cool themselves off through perspiration.
  10. Instinct The most telling comparison is instinct. Humans find fruits and other foods in the natural state appealing and only salivate as a conditioned response to prepared meat. When carnivores see a carcass in the road their natural instinct is to salivate and sniff it in order to determine whether they can eat it. We don't look at a fox or rat running around and think about how hungry we are or try to determine whether or not to pursue the prey. A carnivore's frame of mind is totally geared for hunting and killing. Man's frame of mind is compassionate, friendly and reveres life. When the lion spots another furry animal, something might instinctively click in his head that tells him to hurry up and get dinner. When man spots a furry animal, rather than show his children how to take its life and eat it, a more likely instinct is to pull over, get the camera out and take a picture. Put a young baby chick and an apple in a crib with a six-month-old baby. he will instinctively put the apple in his mouht to try and eat it, and try to play withthe chick. Not the other way round? Man is not a natural hunter. Every predator, in order to go hunting, MUST be hungry. Man cannot go hunting if he IS hungry! He needs the energy to give him strength first. Hunger must precedes a predator going hunting, not follow it. Hunger happens after a man goes hunting not before.

    Humans don’t generally like blood. Our natural instinct is to be upset by it. Some even faint at the sight of it. Those that work in professions where they are ikely to see blood, have to overcome their natural reflex around blood and surpress their instincts.

The animals we are actually closest to in physiology are great apes. Great apes consume almost entirely plant products and only rarely eat insects. Eating meat was simply a response to nutritional stress a long time ago but the stress has long past and we're now able to create plant based foods that efficiently provide all the nutrients we need.

Every species on the planet only consumes dairy from their mothers when they are babies and no species consumes dairy from a different species of animal to their own - other than humans that is. The dawn of the agricultural revolution signified the mass ownership, control, abuse, rape and exploitation of billions of animals animals. Even if humans were biologcally supposed to eat meat, there's nothing natural about the way we treat other living beings.

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