Demographic noise can reverse the direction of deterministic selection.

Area of Science:

• Evolutionary biology
• Theoretical ecology
• Population dynamics

Background:

• Deterministic evolutionary theory predicts altruism leads to extinction by cheaters.
• Standard game theory models often assume fixed population sizes, missing key dynamics.

Purpose of the Study:

• To investigate how demographic stochasticity influences the evolution of cooperation.
• To identify conditions under which cooperation can be favored by selection.

Main Methods:

• Analytical modeling incorporating demographic stochasticity.
• Investigated public goods production and spatial effects.
• Developed a general mathematical framework for stochastic selection reversal.

Main Results:

• Demographic stochasticity can reverse selection, favoring cooperation.
• Larger populations exhibit stochastic robustness, resisting invasion.
• Cooperation can increase population carrying capacity and success, even with reproductive costs.
• Spatial structure amplifies the effect, with implications for microbial populations.

Conclusions:

• Stochasticity, not just deterministic forces, shapes evolutionary trajectories.
• Cooperative behaviors can evolve and persist under realistic population dynamics.
• The findings challenge traditional models and offer new insights into the evolution of social behaviors.