Twenty-four million years ago when our ancestors lived in the tropical forests of central Africa, they probably ate plants and fruit, and from time to time a few insects. When these prehistoric people started to travel north into the savannah their diet changed too, and they began to eat a lot of seeds and other plant material. And this is probably how man lived for the next twenty-two million years, eating roots, seeds, fruits, nuts, vegetables and occasionally a little meat.
The Aztecs and Incas ate a lot of cereals, beans and fruit and not much meat at all. In classical India most people didn't eat meat and the Japanese were mainly vegetarian until a few generations ago. The main food of the slaves who built the Pyramids was boiled onions! Even today, some societies whose lifestyles are unchanged (like the Aborigines of Western Australia) still have mostly vegetarian diets.
During the nineteenth century people in western countries suddenly began to eat a lot more meat. New methods of keeping and killing animals, better transport and new inventions like fridges and freezers meant that meat was suddenly cheaper for ordinary people. It was probably at this time that the typical western meal that millions of people eat every day - meat, potatoes and vegetables - was born.
Also during the nineteenth century, the vegetarian movement started in Europe and the USA. But it was only in the 1960s that more and more people in the west decided to give up meat in their diets. So why do people choose to be vegetarian? Many people decide to become vegetarian for personal reasons. First of all, some people think that it is healthier not to eat meat. Others believe that it is cruel to eat animals. The Irish writer George Bernard Shaw once said, 'Animals are my friends - and I don't eat my friends'. Finally there are some people who think that growing food for cows and pigs to eat is not very economical. Today vegetarianism is more and more popular in Europe and the USA. But in most countries people who never eat meat are still a very small percentage of population.