The oldest traces of human life in what is now France date from approximately 1,800,000 years ago. Men were then confronted by a hard and variable climate, marked by several glacial eras which modified their framework of life and led them to a nomadic life of hunters-gatherers. France counts a large number of decorated caves from the upper Paleolithic era, including one of the most famous and best preserved: Lascaux (Dordogne, approximately 18,000 BC).
At the end of the Last glacial period (10,000 BC), the climate softened and from approximately 7,000 BC, this part of Western Europe entered the Neolithic era and its inhabitants became sedentary. After a strong demographic and agricultural development between the 4th and 3rd millennia, metallurgy appeared at the end of the 3rd millennium, initially with the work of gold, copper and bronze, and later with iron. France counts numerous megalithic sites from the Neolithic period, including the exceptionally dense Carnac stones site (Morbihan, approximately 3,300 BC).
In 600 BC, Ionian Greeks, originating from Phocaea, founded the colony of Massalia (present-day Marseille), on the shores of the Mediterranean Sea, making it the oldest city of France. At the same time, some Gallic Celtic tribes penetrated some parts of the current territory of France, but this occupation spread in the rest of France only between the 5th and 3rd century BC.
The concept of Gaul emerged at that time; it corresponds to the territories of Celtic settlement ranging between the Rhine, the Atlantic Ocean, the Pyrenees and the Mediterranean Sea. The borders of modern France are approximately the same as those of ancient Gaul, which was inhabited by Celtic Gauls. Gaul was then a prosperous country, of which the southernmost part was heavily subject to Greek and Roman influences. However, around 390 BC, the Gallic chieftain Brennus and his troops made their way to Italy through the Alps, defeated the Romans in the Battle of the
