Game Theory and Evolutionary Biology
Resource collection is key to the survival of organisms. But resources are of finite quantities, and many organisms require the same resources. Therefore, organisms must interact with each other as they try to collect resources. The relationships between organisms are varied – organisms can have cooperative, antagonistic, exploitative, and altruistic interactions with other organisms. All interactions have a cost to organisms – energy must be invested into an interaction, whether it is cooperative or antagonistic. Therefore, organisms must weigh the benefits versus the losses incurred to calculate a net benefit – a payoff. In the context of evolution, the strategies organisms use to interact with each other are phenotypes. Success is measured using fitness as a metric. In other words, that is the ability of the organism to pass its genes down through reproduction. If an organism can maximise its payoff by selecting the best strategy (phenotype), it has the greatest payoff since it gets to maximise reproduction. As I have been alluding to, the analysis of strategies and payoffs is game theory, and evolutionary biologists use it as a theoretical framework to study the relationship between organisms.
In evolutionary biology, pure strategies are strategies that are used by a particular organism regardless of who it is interacting with. However, in most interactions, organisms need to use mixed strategies. For example, when two territorial animals are contesting each other, the smaller one might flee to avoid being injured. However, if the same animal were to encounter a smaller animal, it might stand its ground and expect the smaller animal to flee. Smaller animals often are the ones to flee because they have a higher chance of being seriously harmed or even killed. The larger animal has a minimal chance of being injured, so the risks of displaying aggressive behaviour are minimal, making it a useful strategy to employ. When two organisms are of similar size and strength, the risk of both being seriously hurt to the point that they are unable to reproduce increases. To avoid such situations, animals use ritualised displays of aggression. For example, male fiddler crabs engage in displays to compare the size of their claw, and male red deer bellow and exhibit the size of their antlers. Interactions between organisms needn’t always be symmetric – their payoffs could be very different. A typical asymmetric interaction is when an organism tries to intrude on another organism’s territory. The intruder can either gain more territory or not. The current occupier, however, can either maintain its possession of the territory or lose it. Therefore, in this asymmetric game, the current occupier is a lot more likely to escalate into aggressive behaviour than the intruder. Before doing this research, game theory and evolutionary biology might seem like completely discrete subjects. However, from this, it’s clear that evolutionary biology’s strategies are not unlike the strategies in the games we learn about in class.