A Short Demographic History Of Portugal

The Iberian Peninsula, located at the southwestern tip of Europe, is a geographically isolated region. Archaeological evidence indicates that this region has been occupied by humans for at least 400,000 years. It subsequently played a crucial role as a refuge during the Last Glacial Maximum. When the climate warmed about 14,000 years ago, people repopulated the European continent during the Mesolithic. The archaeological remains from this period in Portugal are characterized by the presence of numerous shell middens. Between 5700 and 5600 BC, the Neolithic brought a new way of life to the region with the introduction of agriculture and livestock. This development was brought about by human migrations from Anatolia. In particular, the maritime migrations of these groups brought to Portugal the ceramics of the Cardial culture that reached Portugal around 5500 BC. The latest paleogenomic studies have shown the arrival of a new population despite the persistence of a significant Mesolithic component. The improvement of technology and in particular the emergence of metallurgy resulted in more complex social organizations during the Chalcolithic between 3000 and 2000 BC. These societies are characterized by different regional cultures. In the Bronze Age, changes are observed from 2000 BC, characterized by the arrival of a steppe component in the genome of these ancient individuals. The Iron Age begins around 800 BC. The introduction of iron allows for major advances in agricultural methods, but also in warlike practices. The Celts are located in the north, west and center of the Iberian Peninsula. Phoenician trading posts appear in the southwest. The Roman conquest begins in 218 BC. when Portugal was integrated into the Roman Empire. This period saw the development of urbanization. Roman culture and the Latin language spread throughout the country. In the fifth century AD, Germanic tribes arrived in the Iberian Peninsula. The Suebi dominated the northwest until the unification of the peninsula by the Visigoths . At the beginning of the 8th century, Islamic tribes from North Africa invaded the peninsula, subsequently incorporating it into the Umayyad Caliphate . The Catholic reconquest culminated in the creation of the County of Portugal, then with the creation of the Kingdom of Portugal in 1143. In recent years, some paleogenomic studies have made it possible to study demographic movements during the history of the Iberian Peninsula, but only 51 ancient genomes dated before the Visigoth Kingdom have been analyzed in Portugal so far. 

Xavier Roca-Rada and his colleagues have just published a paper entitled:The genetic history of Portugal over the past 5,000 years . They sequenced 68 new ancient genomes from Portugal dated between the Neolithic and the 19th century. The authors added to these data 590 ancient genomes from the Iberian Peninsula previously published[.]

From here.

The demographic history of Portugal is complex and with old and new ancient DNA and lots of written history from a fairly early point, can be corroborated fairly accurately. It is easy to otherwise assume that an absence of evidence means that everything was simple, a lesson to be taken seriously in less well documented contexts.