%0 Thesis
%A Varas Enríquez, Pablo José
%+ Department of Human Behavior Ecology and Culture, Max Planck Institute for Evolutionary Anthropology, Max Planck Society
%T Variability, resource dynamics, and the human life cycle  : 
%G eng
%U https://hdl.handle.net/21.11116/0000-0011-210D-A
%U  https://nbn-resolving.org/urn:nbn:de:bsz:15-qucosa2-969039
%I Universität Leipzig
%C Leipzig
%D 2025
%V phd
%9 phd
%X <br>The female human life cycle consists of a reproductive career nested between juvenile and post–reproductive periods. Within these boundaries, humans exhibit high variability of life history traits within populations (e.g., life expectancy differs by a factor of 2 and the reproductive output by a factor of 5). The main evolution- ary mechanisms behind such differences are the trade–offs in resource allocation towards survival, reproduction, and development. However, empirical and theoret- ical work have yet to explain how differences in resource availability and acquisition influence the diversity of life cycles observed in human populations. The present thesis focuses on understanding how the variability of resource availability and ac- quisition shape the demographic variability within human populations. First, an empirical analysis is presented about the relationship between the material wealth available and age at first birth in Pimbwe women from Tanzania. Results show that women tend to delay their first birth when they have more material wealth avail- able but accelerate their reproductive onset when they experience higher variability. These results support claims from life history trade offs, such as “(extra) somatic ver- sus reproductive effort' and “current versus future reproduction'. However, they also highlight the lack of understanding of how resources are acquired. Therefore, a theoretical framework is developed to address how the variability of individual resource acquisition, through production and/or transfers, influences the distribu- tion of life history traits. For this, an agent-based model is designed, where indi- viduals experience stochastic resource production and resource transfers governed by a stage–structured stochastic blockmodel. Resource allocation towards survival, reproduction, and development is deterministic. This model helps elucidate how resource production and transfers relate to life history traits while remaining agnos- tic to other factors (e.g. kinship, social status), allowing to further understand the relationship between the variability in resource acquisition and demographic diver- sity. The results indicate that the greatest variability in longevity, lifetime reproduc- tive output, and age at first birth occurs in contexts where resource transfers are involved. As individual probabilities of resource production increased, the variabil- ity in both longevity and lifetime reproductive output also rose, while the variability in age at first birth remained unchanged. In contrast, the variability of life history traits associated with resource transfers exhibited fluctuations without a consistent pattern. Moreover, the inclusion of resource transfers resulted in individuals liv- ing longer, producing fewer offspring, and displaying a broader range of ages at first birth. These results align with the idea that resource transfers have a buffering effect against environmental uncertainty, allowing more similar life cycles by the re- distribution of resource within the population. In conclusion, this thesis addresses the complexity of how resource variability, either its availability or acquisition, in- fluences the female human life cycle, and provides insights into the mechanisms driving the demographic diversity within human populations.