The Iberian Peninsula has been inhabited for at least 500,000 years, first by Neanderthals and then by modern humans.
Galicia, northern Portugal, Asturias, western León, and Zamora formed a single megalithic area since the Neolithic and Chalcolithic (also called Copper Age) Ages, around 4500–1500 BC.
This was the first great culture to appear in Galicia and was characterized by its surprising capacity for construction and architecture. This was combined with deep sense of religion, based on the cult of the dead, the mediators between man and the gods.
Many historians believe that Megalithic culture had two sources: an oriental source that was predominant in the Mediterranean area, and one in the Atlantic, which originated north of the Tagus River. The latter, because of its geographical proximity to Galicia, would explain the abundant traces of megalithic culture in this area. That this should be the first great culture also meant that it constituted one of the basic pillars that was to endow Galicia's cultural personality.
From this era there remains thousands of dolmens (mámoas), a type of tomb or sepulchre, throughout the entire territory. From its social organization it has been confirmed that it corresponded to some type of clan structure.
The introduction of bronze-working techniques introduced a new cultural stage, when the new importance of metals resulted in intense mining activity. Some historians attribute the boom in this sector to the extremely dry and warm climate of the time which revealed, due to the resulting erosion, the mining richness of the North.
Peoples from the Castilian plateau moved to Galicia, thus increasing the population, because its position near the Atlantic Ocean gave it a very humid climate.
The increase in population caused certain conflicts, but also led to increased mining and production of weapons, useful objects, and ornamental objects of gold and bronze. Pieces of jewellery crafted from Galician metals circulated throughout all of the Peninsula and Europe.