The first "ovens" date from the earliest agrarian period of human history, the time of the first permanent human settlements.
The oven developed with the first food humans knew how to cook: grilled cereals, then flatbreads and finally leavened bread. Leavened bread is said to have been invented by accident some 5000-6000 years ago in the Near East: flatbread dough which had been put aside for some time began to naturally ferment and rise before it was cooked !
Since then, through different periods and cultures, humans have continuously improved techniques for cooking bread, eventually creating the wood oven we know today.
These civilizations were responsible for the first bread ovens (around 5000 years ago). A large clay pot was placed upside down over the hearth and coals. After the clay pot was heated the flatbread or dough was placed inside and cooked for the first time with heat from all sides.
This basic oven was later improved by the development of the first "Tandur" oven, still used today, notably in Pakistan to cook the famous "Naan" bread.
These ovens were made from clay and straw and shaped like a waist high, tapered, open-topped barrel. Fire and live coals in the barrel heated the oven. Baking bread was a well organized activity which took place in real bakeries, and bread was so important it was used as payment in kind for salaries and taxes.
« Having bread and water, I revel in the pleasures of the body » Épicure (341 - 270 B.C.)
It was the Greeks, masters of art and bakery, who invented the "modern" wood oven, which has hardly changed in 2000 years ! They had the idea of "laying down" the Egyptian Tandur oven to position it on the ground with the opening at the front. This way, the oven was more practical and used less wood. Soon, they added an oven floor where the fire could be built. Finally, they came up with the bright idea of removing the fire at the end of cooking to cook the food with waves of heat.
These Greek techniques were imported by the Romans and applied, developed and exported throughout the Roman Empire.
Although the Romans did not bring any major changes to the Greek oven design, they did introduce a new basic material, earthenware bricks.