EFCHED
Advanced computer modelling of hominin dispersal from Africa: integrating archaeological and palaeoclimatic simulations
This project combined expertise from the fields of climatology and archaeology in order to develop a new computer model for exploring, through simulation, hominin dispersal out of Africa.
Our process-based approach builds on the Stepping Out model of hominin colonisation developed a number of years ago by Professor Steven Mithen of Reading University. It also incorporates information from palaeoclimatic simulations by Professor Paul Valdes of Bristol University which were completed using the Hadley Centre climate model.
The methods developed during this project provide a powerful method for integrating genetic, fossil, archaeological and climate data, to increase our understanding of prehistoric migration.
Four of our major achievements
1. Using the Stepping Out model, an investigation of early hominin dispersal out of Africa around or soon after 1.8 million years ago was undertaken for Homo erectus.
Image: Homo erectus occupation at 1ma resulting from colonisation most consistent with the observed record of arrival (100%=black, 0%=white).
Arrival dates for hominins in Europe and south-east Asia were investigated, in particular exploring the combined effects that bridges and barriers, and environmental and climate change would have had on dispersal patterns between 1 and 2ma.
Known fossils suggest that hominins arrived in Europe several hundred thousand years after being present in Asia, suggesting relatively lower survival rates in Eurasian landscapes.
This study has extended our understanding of the results from Mithen's original study.
We used climate models to improve the representation of climate and vegetation patterns. This showed that integrating climate models and hominin dispersal models can provide new insights and improved confidence in interpreting the data.
2. We simulated genetic drift and the homogenising effects of inter-group contacts amongst Homo erectus populations using an enhanced version of Stepping Out.
We examined the amount of gene flow between regional populations and the effects of separation from the source population.
The most significant genetic feature suggested by the simulations is that a division between the African and Asian populations of Homo erectus is the natural consequence of bio-geography.
Image: Homo erectus diversity relative to east African populations. Major fossil sites are represented by white markers; the colour scale illustrates increasing divergence away from east African populations.
The separation of African and Asian hominin populations has been much debated in the literature. The effects of behavioural, geographical and environmental factors on this division as well as other genetic patterning has been considered through a suite of additional simulations. Throughout the study, the modelling results were interpreted in the context of fossil records to enhance our understanding of the population history of Homo erectus.
3. Stepping Out provides an excellent tool for considering gene flow in a real world context, since it can explicitly simulate the movement of populations. It is also well suited to developing long-term studies of regional population histories under alternative migration scenarios.
The results from initial simulations have been interpreted in the context of spatial patterning of early Palaeolithic industries, as well as the dispersal of Homo sapiens out of Africa around 200 thousand years ago.
Both have successfully demonstrated the applicability of the model to later prehistoric migration.
4. With colleagues from Liverpool John Moores University, we successfully adapted and applied the Stepping Out model to the investigation of the migration of an extinct species of Theropithecus.
This summary was compiled by John Hughes (Bristol). Paul Valdes (Bristol) is the PI for this project.
The research outlined here was undertaken with Bruce Sellwood (Reading), Steve Mithen (Reading), Sam Smith (Reading), Alan Haywood (British Antarctic Survey), Sarah Elton (Hull) and Hannah O'Regan (Liverpool John Moores).