Biocultural Evolution in Upper Pleistocene Western Eurasia and the Possible Explanation for the Disappearance of Neanderthals
Citation: BARTON, C. MICHAEL; RIEL-SALVATORE, JULIEN. Advances in Complex Systems. Mar2012, Vol. 15 Issue 1/2, p1150003-1-1150003-24. 24p. In the process of human evolution, there is a complex interaction between changes of social behaviors and biological changes which both are key perspectives to study the process of evolution. However, in the current generation of paleoanthropological studies, paleoanthropologists often only focus on the evolution of human genomes and physical characters, with the behavioral changes being thought as the consequent result of biological changes. On the other hand, the study of biocultural evolution is different from study of biological evolution and cultural evolution. It focuses on the dynamic relation with the biological factors and environmental factors and their influences on the subject which we study. Related to the disappearance of Neanderthals, they were widely thought to be replaced by anatomically modern humans (AMB) during the Upper Pleistocene with almost no gene communications. In this study, the researchers focus on the human biolcultural evolution in Western Eurasia at Oxygen Isotope Stage 3 and find the possible explanation for the disappearance of Neanderthals from the biocultural perspective through applying computational modeling environment to reconstruct the population-scale interactions between AMB and Neanderthals with the parameters from archaeological data. In the experiment, the researchers first gave out three possible factors that might lead to the disappearance of Neanderthals. The first possibility is lower fertility or higher mortality than AMB. The second possibility is the mating barrier, which may exist between Neanderthals and AMB, contribute to the reduced fertility of AMH or Neanderthal hybrids, and also may also be caused by the advantages of AMH or Neanderthal hybrids, decreasing the possibility of Neanderthal to reproduce offspring. And the third possibility is the difference on residential mobility strategies (RMS) of Neanderthals and AMH, which may increaser AMH’s possibility to reproduce offspring and restrict Neanderthals from reproducing offspring. Then the researchers apply an agent-model to represent the three possibilities in quantitative, algorithmic form, with the agent 1 representing Neanderthals, and the agent 2 representing AMB. For example, to exert restrictions on the lifetime of Neanderthals, researchers simply input a number in the special area so that the type of agent will disappear on the screen if it reaches its restriction of lifetime. And also, there are other parameters through which the researchers could control the variables, such as fertility, mortality, mating barriers, and the RMS. The experiment was replicated 10 times, with the same condition, which is the schematic map of Upper Pleistocene western Eurasia, a smaller number of agents on the left, representing Neanderthals, and a larger number of agents on the right, representing AMH. The outcome is unpredicted and different each time; however, based on the result, researcher conclude that the fitness advantages of AMH, which is higher fertility and lower mortality and higher land-use and mobility of AMH could lead to the disappearance of Neanderthals. It was because the number of Neanderthals was fewer than the number of AMH, consequently, as the increased mobility, more AMH offspring would be reproduced than Neanderthals which would further expand the disparity of population between Neanderthals and AMD. However, the socially-mediated controls on mating only have little to no impact on the rate of gene flow between AMH and Neanderthals over long time spans. According to paleoanthropological records, compared to Neanderthals, AMH had a