For most of human history, people did not cook their food. They simply ate it the way it was found. Thousands of years ago, people learned how to use fire for cooking purposes. However, humans have long been interested in using the heat from the sun to cook their food, as well. An ancient group of people called the Essenes lived in the northern part of Aftica about 2000 years ago. Records indicate that they heated thin pieces of bread on rocks that were wsrmed by the sun.