Climate Change and Culture Change

Let’s turn from Bolores and Zambujal and consider the bigger picture – specifically, the relationship between human history and changes that occurred between 4000-1000 BCE in the climate and environment of the Iberian Peninsula. How do we get at these complex issues? Archaeologists as well as environmental scientists use proxies, or indirect evidence, which provide clues into past behaviors or environmental dynamics. For our study, we incorporated a number of proxies, including delta 13C values of plants, which tell us about ancient vegetation and precipitation, pollen cores, which tell us about vegetation and climate, and radiocarbon dates, which tell us about population dynamics. Isotopes are ‘found’ in the bone structure of humans and animals and in phytoliths, or microscopic fossilized plant remains. Pollen is extracted from the ground by drawing out long cores from the ground and looking at the remains of pollen. These can be dated through stratigraphic principles or directly through radiocarbon dating. The study of pollen is called palynology.

As with much of the research, the investigation of climate change and culture changes requires expertise from different specialists. For this study, I invited three other specialists to collaborate with me:

-American archaeologist, Brandon Lee Drake, who specializes in reconstructing ancient climates using different proxies,

-Spanish archaeologist – Antonio Blanco-González, who has written about, among many things, climate change in Spanish prehistory, and

-Spanish palynologist – or pollen expert, Jose António López Sáez, who has written about Holocene climate changes and their relationship to cultural transformations in Iberian prehistory.

For our study, we were particularly interested in tracing the relationship between cultural changes between the Copper Age and Bronze Age in three regions of the Iberian Peninsula (the Northwest, Southwest, and Southest) and the Bond Event 3, a climate event that led to increased aridity around 2200 BCE.

What did we learn? We found that the wettest Northwest region features the most stable trend lines, whereas the Southwest exhibits an abrupt decrease in its demographic signals c. 2500 cal. BCE, which is then followed by a subsequent rise in the neighbouring Southeast. These lines of evidence suggest the possibility, never previously noted, of a population shift from the Southwest to the Southeast in the Early Bronze Age as a contributing factor to the cultural dynamics of southern Iberia. They also suggest that the Bond Event 3 cannot be used to explain the changes of the Early Bronze Age, as important demographic and environmental changes occur prior to it.

To hear and see more about our results: