Dresden 2026 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 33: Statistical Physics of Biological Systems I (joint session DY/BP)

DY 33.11: Vortrag

Mittwoch, 11. März 2026, 12:15–12:30, ZEU/0114

Darwin's paradox of the peacock tail: a stochastic perspective on sexual selection — •Ian Magalhaes Braga — CASUS, Gorlitz, Germany

Many species show male traits that are extravagant, costly, and seemingly disadvantageous, yet they evolve and persist. Classical explanations especially deterministic versions of Fisher's runaway struggle to fully account for this pattern, mostly because they ignore the inherent randomness of evolutionary processes. In this work, I propose that stochasticity is not a secondary detail but the key element that reshapes the dynamics of trait preference coevolution. Treating sexual selection at the microscopic, probabilistic level reveals a simple but unexpected idea: in finite populations, a costly trait can actually support the evolution of female preference. I refer to this effect as the cost advantage. The basic picture is that stochastic fluctuations change the timing of fixation events, creating conditions under which preference benefits from the very cost that penalizes the trait. Using large-scale simulations across multiple evolutionary architectures, I show that this behavior is general and does not depend on specific modelling choices. The results suggest that costly ornaments are not paradoxical after all they may simply reflect the true stochastic nature of evolutionary change.

Keywords: Peacock's paradox; Evolutionary dynamics; Stochastic process; Sexual selection; Fixation probability