Are you a carnivore, a vegetarian or a Vegan? Are you lactose intolerant or do you have a peanut allergy? What do these things mean and how do they define us and our society?

To start with, few if any of us are true carnivores. Our species developed as omnivores, the literal meaning of which is that we eat anything. More accurately, our digestive systems are best adapted to a mixture of food sources. Most species have a very narrow diet, not by choice but by evolution and adaptation. Cows eat nothing but grass and most higher predators nothing but meat, but we - along with other primates and some rodents - are opportunists who derive essential nourishment from whatever comes along that's slower than we are.

Human society developed along with our palate. Our earliest ancestors were scavengers, picking nuts and berries plus whatever carrion hadn't already been claimed by someone bigger or badder than ourselves. Once we learned to work together we became able to drive off competitors who had already made a kill, just as hyenas and baboons do today. We then developed our group skills to do our own killing, but rather than evolve into a species of meat-only eaters we continued to forage and maintained a wide diet.

As our evolution continued, hunting gave way to farming, where the animals on which we depended were contained and managed, providing a consistent, reliable food source that would permit the faster development of society. Interestingly, although we farm animals on land, at sea we hunt just as in our distant past, and the consequences of over-extraction are becoming all too obvious.

As our society developed and our numbers grew, our food patterns changed too, and this has mostly to do with the economic cost of different kinds of food. In ecological terms, meat-eating is a luxury afforded to relatively small groups. Carnivores are at the top of the food chain and depend on the availability of prey in sufficient numbers. It is not in the interests of a hunter to wipe out all his prey. Let's not beat about the bush; being a carnivore means - with few exceptions - killing other animals, and since we need to eat every day this means quite a lot of prey animals for every predator. It's a pyramid with the carnivores at the top, their prey in the middle and a lot of vegetation at the bottom.

Human society has been phenomenally successful, to the extent that we make the food pyramid top-heavy if we allow every member of our species to occupy it. For this reason, poorer societies eat very little meat, not by choice but by economics. The traditional dishes of southern Italy are replete with tomatoes, peppers, zucchini and garlic, while the introduction of the potato to Ireland in the early 1500s led to a population largely dependant on just this one food, with disastrous consequences in 1845 and the following years when a fungus destroyed the crop, causing the potato famine. A similar fungus is now decimating the tomato crop in New England (tomatoes are related to potatoes) and threatens to destroy every plant on the eastern seaboard.

In the developed world, food is a lifestyle choice for most people. The great majority choose to be omnivores, perhaps partly because since most of us have little contact with farm animals there is a comfortable distance between the live animal and the pre-packaged meat at the supermarket. For a large number of us, being made aware of the steps in between will force a re-appraisal of lifestyle in the direction of vegetarianism. An abattoir is an unpleasant place, though unfortunately necessary for us to maintain our omnivore lifestyle, and becoming a vegetarian is a valid and usually ethical response. It is however surprisingly difficult to define vegetarianism and I'll return to this in the second part of this article.

Veganism

The term Vegan was coined in 1944 by Donald Watson and Elsie Shrigley as a response to the broadening of the term "vegetarian" to include dairy products. The Vegan Society defines veganism as

"a philosophy and way of living which seeks to exclude — as far as is possible and practical — all forms of exploitation of, and cruelty to, animals for food, clothing or any other purpose; and by extension, promotes the development and use of animal-free alternatives for the benefit of humans, animals and the environment. In dietary terms it denotes the practise of dispensing with all products derived wholly or partly from animals".

Of all forms of diet, a vegan one is probably the simplest to define, understand and indeed justify. It does however require careful application in order to maintain essential nutrients that are normally associated with animal products, and is often not recommended for groups with enhanced risks. This is tantamount to claiming that veganism is not a "natural" choice for human beings, but of course very little of our lives can be described as "natural". We manage everything around us so why not take the same care with diet as we do with every other aspect of our lives? A vegan diet is easier to maintain in warmer climates than in colder; in northerly countries many of the more interesting ingredients have to be imported, though growing under glass - potentially another disruption of the "natural order" - can bring these ingredients to the table without the need for large transport costs.

It's worth noting that being a vegan is easier in some cultures than in others. I've heard it said that asking in a restaurant for a vegan dish is easier in Italy than in many other countries; could this be a legacy of the "cucina povera" from the South, which includes no animal products because of their scarcity?

In Part 2 I examine meat-eating, vegetarianism and food allergies.