There are two main periods of agrarian improvement in the Iberian peninsula, the Copper Age/Bronze Age transition and the late Bronze Age/Iron Age transition, associated with the use of the plough, traction, and methods of increasing soil fertility, such as fertilising and the growing of legumes. Both were related to changes in women's inheritance. Improvements in agrarian technology appeared first in south-eastern Spain and their consequences are visible in the grave goods of the Argaric tombs. From the late Bronze Age on, the rest of the peninsula underwent similar changes. At the same time precious metals changed their meaning: from being a gift to becoming a commodity and therefore they were increasingly scarce in graves. Although there is evidence of the exchange of women during the Iron Age, they were high-ranking women, such as those of the El Carpio and Aliseda tombs, who transmitted political rights to their descendants. Yet evidence from archaeology, epigraphy, and Roman chroniclers point to the maintenance of a primitive agriculture and matrilineal practices in some parts of northern Spain until the Roman conquest.