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A study reconstructs last hunter-gatherer population dynamics in Portugal during the Pleistocene-Holocene transition

Carried out by researchers from the University of Alicante (Spain) and the University of Algarve (Portugal), the study confirms that they adapted very well to the 8.2 kyr ago event, where the global temperature of the planet dropped by about 2ºC, reorganising the distribution of their settlements and exploiting the water resources of the Tagus and Sado rivers more intensively

 

 

Alicante, Monday 8 February 2021

A study by researchers from the University of Alicante (Spain) and the University of Algarve (Portugal) reveals the demographic changes of the last hunter-gatherer populations in Portugal during the Pleistocene-Holocene transition, between 18000 and 8000 years ago. They work has been published in the prestigious scientific journal Philosophical Transactions of the Royal Society B, and has major implications for the study of population adaptations to climate change.

In particular, the research team has analysed Carbon 14 dating (a radiocarbon dating technique to measure the age of archaeological remains) to reconstruct relative changes in population size and analyse their relationship with changes in diet and settlement systems during this period, characterised by major climatic changes and environmental transformations. 

The work has great implications for understanding how hunter-gatherer populations adapted to climate change by modifying the way they occupied the territory and their diet, as explained by Javier Fernández-López de Pablo, author of the study and distinguished researcher of the Gen-T Plan (Valencia region programme to support talented researchers) assigned to the University of Alicante Institute for Research in Archaeology and Historical Heritage (INAPH). The experts have presented a complete reconstruction of the demographic dynamics during the end of the last glaciation and the beginning of the Holocene on the Atlantic coast of the Iberian Peninsula, an area where the last hunter-gatherer populations faced rapidly changing environments and climatic conditions. In this sense, this archaeological study offers an insight into how past human population ecologies changed in response to this scenario.

 

Results

The researchers have identified a first phase of population growth during the late Pleistocene interstadial period (around 14,800 years ago) and the beginning of the cold climatic episode of the Younger Dryas (12,800 years ago). This last episode of climatic deterioration seems to be associated with a contraction in the size of the population whose territorial distribution would show a more dispersed pattern.

In addition, the study points to a final phase of population growth that began around 8,300 years ago, coinciding with the 8.2 kyr ago event in which the global temperature of the planet dropped by about 2ºC, and the change in marine currents increased biological productivity in the estuaries of the Tagus and Sado rivers. According to the UA distinguished researcher, the settlers began then to concentrate around these areas, which allowed a more intense exploitation of water resources, as well as a rapid demographic growth.

As Fernández-López de Pablo explained, unlike what has been observed in other regions of the Iberian Peninsula, this case study shows a strong correlation between population growth and the changes in marine productivity observed in the estuaries. These populations were able to generate successful adaptive responses in both diet and settlement pattern during the Mesolithic period, around 8,300 years ago, but also because of a greater dependence on marine food sources.   

 

Methodology

The team of researchers who authored this article have worked for two years on the analysis and study of data from around 70 prehistoric sites along the Atlantic coast, more than 370 radiocarbon dates, and human remains to obtain information on Paleo diet. This is undoubtedly the first scientific study focused on the Atlantic side of the Iberian Peninsula that covers such a long period of time, as the UA expert stated. In addition, they have developed new quantitative methods to create time series with which to trace changes over time in population size, distribution and changes in diet.

 

Reference:

“Late Glacial and Early Holocene human demographic responses to climatic and environmental change in Atlantic Iberia”, Philosophical Transactions of the Royal Society B. November 2020. https://doi.org/10.1098/rstb.2019.0724

 

Articles related:

UA researcher Javier Fernández-López de Pablo co-edits a special issue on prehistoric demography in a publication of the Royal Society

Researchers from the universities of Alicante and Barcelona propose a new model for analysing social networks in prehistory

 

 mapa1.jpg

  

Figure 1. Maps showing: a) the location of the Atlantic coast of the Iberian Peninsula; b) the distribution of post-Last Glacial Maximum (LGM) hunting and gathering sites in the study region; and c, d) the concentration of Late Mesolithic sites in the Muge and Sado estuaries, respectively

 

 

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