Extended Parental Investment Effects on Population Dynamics: From AI Agent Modeling to Real World Demographics

Parental care is prevalent, especially among mammals. A long-lasting research question lies in whether Post-Maturity Parental Investment (PMPI) has any behavioral or physical population effect. However, it is ethically inconceivable to directly experiment on real mammals in a sizable manner. Therefore, AI agent populations with and without PMPI are proposed to examine the population-scale consequences under different scenarios. Specifically, both multi-agent reinforcement learning (MARL) experiments and multi-agent simulation (MAS) experiments are proposed for investigating the PMPI effects on population dynamics. MARL tests the behavioral aspect (learning) while MAS tests the physical aspect (survival). Based on millions of simulated steps, the results suggest that PMPI secures lineage successions and leads to family-dominated formations at individual level. However, at population level, PMPI is negatively correlated with population size and total wealth, while being positively correlated with wealth inequality (as measured by the Gini index). Both experiments suggest that extended parental investment (e.g., PMPI) imposes systemic constraints on population dynamics. On the other hand, those simulated results can be corroborated by real world demographic data from global authoritative sources. The MAS source code, executable, and web version is available for scientific reproducibility at https://www.cs.toronto.edu/∼wkc/ParentalCaresOnline.html.