| dc.description.abstract | Although play-fighting is widespread among juvenile mammals, its adaptive significance remains
unclear. It has been proposed that play is beneficial for developing skills to improve success in adult
contests (motor training hypothesis), but the links between juvenile play-fighting and adult aggression
are complex and not well understood. In this theoretical study, we investigate the coevolution between
juvenile play-fighting and adult aggression using evolutionary computer simulations. We consider a
simple life history with two sequential stages: a juvenile phase in which individuals play-fight with
other juveniles to develop their fighting skills; and an adult phase in which individuals engage in
potentially aggressive contests over access to resources and ultimately mating opportunities, leading
to reproductive success. The simulations track genetic evolution in key traits affecting adult contests,
such as the level of aggression, as well as juvenile investment in play-fighting, capturing the
coevolutionary feedbacks between juvenile and adult decisions. We find that coevolution leads to one
of two outcomes: a high-play, high-aggression situation with highly aggressive adult contests
preceded by a prolonged period of juvenile play-fighting to improve fighting ability, or a low-play,
low-aggression situation in which adult contests are resolved without fighting and there is minimal
investment in play-fighting before individuals mature. Which of these outcomes is favoured depends
on the mortality costs and on the type of 27 societal structure: societies with strong reproductive skew,
favouring monopolisation of resources, show high levels of adult aggression and high investment in
juvenile play-fighting, whereas societies with low reproductive skew have both low adult aggression
and low levels of play-fighting. A review of empirical evidence, particularly in the primate genus
Macaca, highlights some limitations of our model and suggests that other, complementary functional
explanations are needed to account for the full range of competitive and cooperative forms of play
fighting. Our study illustrates the power of evolutionary simulations to shed light on the long-standing
puzzle of animal play. | en_GB |
