The most reply in the world when you tell someone you’re a vegetarian is, ‘But we’re meant to eat meat!’ Let’s get it straight right now, we are not meant to eat meat. Humans are not carnivores like cats; we’re not even omnivores like a pig or a bear.

If you really think you’re meant to eat meat, try running into a field, jumping on the back of a cow and biting it! You wouldn’t even be able to get your teeth or fingernails through its skin. Or try picking up a dead chicken and chomping on it; we just don’t have the teeth for eating meat without cooking it first.

We are in fact herbivores - and that doesn’t mean a creature like a cow with four stomachs that spends all day munching grass. Cows are ruminants; herbivores eat a whole range of vegetable foods, like nuts, seeds, roots, shoots, fruits and berries. How do I know this? Because numerous studies have been done on what apes eat. The gorilla, for example, is entirely vegan.

An eminent doctor, David Ryde, one-time medical adviser to the British Olympic Association, once tried a little experiment. He displayed two pictures at a medical exhibition. One was of a human’s intestines; the other of a gorilla’s intestines. He then asked his colleagues to look at them and make any comments. All the doctors present thought both pictures were of human beings and not one identified the gorilla.

I know it doesn’t go with Nike trainers, Benetton jumpers and Oxy-10 spot remover, but that’s what we are – apes. Over 98 per cent of our genes are the same as a chimpanzee’s and any visitor from space trying to work out what type of animal we are would immediately classify us as a type of chimp. They’re our nearest relative. Terrible that, when you think of the disgusting things we do to them in laboratories.

A good indicator of what our diet would naturally be is to watch our ape relatives in the wild. They are almost entirely vegan. Some eat a little meat in the form of termites or maggots (very tasty) but this accounts for a tiny part of their overall diet. A scientist called Jane Goodall lived in the jungle alongside chimps and studied them for ten years. She made a note of everything they ate and was able to show exactly how much of it was meat – it was the equivalent amount to a pea a day. So little, in fact, that their teeth and gut are those of a vegan.

However, the ‘we’re meant to eat meat’ brigade got very excited when naturalist David Attenborough showed a film on TV of one particular group of chimpanzees hunting and eating colobus monkeys. They said this was proof that we’re natural meat eaters.

There is no real explanation for this group of chimps but they do seem to be the exception. Most chimpanzees don’t go looking for meat and never pick up frogs and lizards or other small creatures from the forest floor, although they are there for taking. It’s thought that their liking for termites and maggots is because of their sweet taste.

A good way of telling what an animal is supposed to eat is by looking at its body. An ape’s teeth, like ours, is made up mostly of flat surfaces for crushing and grinding. Our jaws are also designed to move from side to side to help this process. Both these characteristics are the signs of a mouth designed to cope with tough, vegetable foods full of fibre.

Because foods of this type are difficult to digest, the process starts as soon as the food is in the mouth when it’s mixed with saliva. The chewed up mass then passes through the body very slowly, snaking its way through the long intestines so all the nutrients can be absorbed.

Meat eaters, like cats, are built completely differently. Not only does a cat have claws to grab hols of its prey but its teeth are sharp, with no flat surfaces. Its jaw can only move up and down in a chopping motion and the animal bolts its food down in big chunks. It doesn’t need a cookery book and British Gas to help digest it either.

The inside of a carnivore’s stomach is a bubbling mass of acid that would take the paint off a car. It’s designed to break the meat down quickly so the poisons released by the meat as it decays don’t hang around too long. Its intestines are short, about three times the length of its body when stretched out in one line, and are designed to get the waste out of the body as quick as possible.

Imagine what would happen to a piece of meat if you left it on a window sill on a sunny day. It wouldn’t take long before it began to rot and produce poisonous toxins. This process can also happen inside the body which is why animals which are meant to eat meat get rid of waste as quickly as possible. Human digestion is much slower because our intestines are about 12 times the length of our bodies. This is thought to be one reason why colon cancer is much higher in meat eaters than in vegetarians.

Obviously humans did start eating meat at some time in history, but for the majority of people in the world right up into this century, meat was a comparatively rare food and most people ate it only three or four times a year, usually at big religious festivals. It’s only really since the Second World War that people started eating meat in such huge amounts – which may explain why heart disease and cancers have suddenly become the biggest killers of all known diseases. One by one, all the excuses used by meat eaters to justify their diet have been demolished. The weakest one of all is that we’re meant to eat meat!