Are Humans Meant To Eat Meat
Human animals in the UK, consume on average 14% of their calories as meat. However as the vegan movement is gaining momentum, the question of whether or not humans are actually supposed to eat meat is hotly debated across social media. Arguments on both sides compare humans to lions or animals that have evolved to eat plants. 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 continuous monitoring of internal conditions and keeping them within a normal range. When it comes to maintaining nutrition, an animal needs to be able to identify the most biologically appropriate foods. It does this through signals sent back to the brain by its cells and organs after digesting a meal. Depending on the benefits, toxicity or lack of benefits to the body, the flavour of a food is recorded as either ‘good’ or ‘bad’. Biologically appropriate foods provide the strongest positive nutrient feedback, and the animal will deliberately seek out foods that smell and taste similar. An animal will also (usually) stop eating a particular food if it starts to receive negative feedback.
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’. The flavour of bacon has nothing to do with pork and results from a mixture of fat, smoke and salt, which is why many bacon flavoured crisps are suitable for vegans. Refined foods with unnaturally high amounts of added sugar might boost our mood and energy levels making us feel good temporarily, but are they nutritionally good for us? Likewise foods designed to have an artificially sweet taste may actually 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, in our unnatural highly processed world where what tastes and feels good has very little to do with our maintaining homeostasis, 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 dentition and the anatomy of digestion - so we decided to take a look.
A commonly held view is that the presence of canine teeth indicates that an animals diet should be meat based. However the presence of canine teeth alone isn't enough to determine the diet that an animal evolved to eat. Nearly every animal on the planet possesses canine teeth, even great big herbivores so it’s more useful to look at the entire dental anatomy. True carnivores have sharp pointy cheek teeth (carnissials), as well as sharp pointy canines. They need these rows of sharp teeth to catch and hold onto prey, tear it apart and crunch down on those bones! 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. Human dentition is consistent with a biological diet designed to include plants not prey.
- 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. Like humans the jaw joint of a herbivore on the other hand, is positioned above the level of the teeth, enabling a much bigger range of movement. This mechanism has evolved through extensive chewing, crushing and grinding of grains and other high fibre foods. The jaws of humans, are also very weak and dislocate easily when subjected to too much force - which means wrestling a hog with your bare hands and mouth should be taken off your bucket list for now
As juveniles and adults, carnivores drink water by scooping it up with their tongues curled backwards. This backwards curling tongue motion forces water into a column and up into their mouths. Humans, like herbivores, are incapable or creating this backwards tongue hook. Watch herbivores (like cows and horses) drinking at a water trough, and you'll see that they drink by sucking. Alternatively place some water in your cupped hands and observe your natural instinct. Do you try and curl your tongue backwards to lap it up, or do you naturally lean towards sucking it up using your cheek muscles?
The saliva of a carnivore doesn’t contain the digestive enzyme amylase and instead they swallow large chunks of prey whole. The digestive process bypasses the mouth and is started by the stomach where 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 and start breaking it down. Human saliva contains digestive enzymes (amylase and lipase), which begin the process of digestion.
- 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. You can eat grass but if you eat a lot of it you will be sick. Our stomachs and cecum are no longer used to coping with large amounts of grass, and both have shrunk over time in response to changes in our diet. It's is a commonly held misconception that humans don't have a cecum and this fact is often misused as a 'mike drop' moment by carnivores - we still have a cecum, but it's very small now.
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). Comparing humans to ruminants is unhelpful because many animals can digest grass, but some (like ruminants) are much better at it than others.
Obligate carnivores (like cats and dogs) can only consume very small quantities of grass and even a few mouthfuls can be enough to cause emesis. For this reason obligate carnivores (such as cats and dogs) may deliberately eat small amounts of grass in order to make themselves sick. The same way that big cats in the wild use grass to purge indigestible parts like feathers, fur and bones. Big cats also need to poo too, so they obtain fibre from plant matter to promote regular bowel movement, cleanse the intestines 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 animals, which is rich in minerals like folic acid. In summary - all animals eat plants, even those big lions that we are often compared, but some animals like ruminants have a system that is optimised for obtaining nutrition from grass.
- 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 in general. 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 very acidic stomach with a gastric pH of 1.9. Both of these figures are counter intuitive and 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, that eat rotting or putrefying flesh are most likely to encounter high levels of pathogens, whereas herbivores have the least exposure to possible pathogens and therefore less acidic stomachs. It’s interesting to note that humans, (uniquely among the primates), appear to have stomach pH values more akin to those of carrion feeders and scavengers. 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 our poor track record with fecal-oral pathogens, which have infected and killed many humans in the past.
A large body of literature now suggests that this adaptive lowering of our stomach PH has caused a variety of human medical problems, related to the loss of mutualistic gut microbes. Whenever we lose gut symbionts, (for example when we take antibiotics), our highly acidic stomach filters, combined with our now very small cecum, means that the chance of re-colonising new symbionts are low.
Animal flesh is composed of the most highly complex type of protein that exists and requires vast amounts of uric acid to break it down into amino acids. Uric acid is a highly toxic substance thought to be responsible for the ageing process and must be flushed out and dealt with, which is one of main functions 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 a human or other plant eater. Consuming large quantities of meat is toxic to humans and can cause many complications such as gout.
The gait, large paws and claws of a predator enable it to hunt, chase and trap its prey. Their appendages are tools meant to kill. Man's gait, is designed only for mobility. Also examine your hand, fingers and fingernails. Are these the apparatus designed for catching, trapping, killing and ripping apart cattle and pigs? Now consider picking berries, picking and peeling fruit from trees or harvesting vegetables. The food your hands have evolved to deal with are typically high in water content, high in fibre, and collectively contain every vitamin and mineral necessary to sustain human life.
- 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.
The most telling comparison is instinct. Humans find fruits and other foods in their natural state appealing. We only salivate as a conditioned response to meal times and eating prepared meat. When a carnivore see a carcass in the road their natural instinct is to salivate and sniff it in order to determine whether it is safe to eat. Humans don't look at a fox or rat running around and try to determine whether or not to pursue the prey. A carnivore's frame of mind is totally geared for hunting and killing. When not clouded by toxic masculinity man's frame of mind is compassionate, friendly and reveres life. When a lion spots another furry animal, something might instinctively click in his head telling it to hurry up and get dinner. But humans are not natural hunters. Predators use hunger as a precondition to hunting - Humans on the other hand do not have enough energy to hunt if they are hungry. Humans also don’t generally like blood. Our natural instinct is to be upset by it and some people even faint at the sight of it.
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. Humans are not biologically supposed to eat meat, however even if they were, there's nothing natural about the way we treat other living beings.