Why do animals sometimes fight to the death for resources, while other times they prefer to avoid conflict or even help each other? To answer this question, scientists use game theory. Game theory is a mathematical approach that allows them to model interactions and predict their outcomes. In biology, game theory helps explain both competition and cooperation, as well as mysterious phenomena such as altruism.
Interaction as a Game
Any interaction between organisms requires energy. Conflict, flight, or even cooperation all cost resources. Scientists refer to the profit or loss from behavior as a “payoff.” Strategies that bring the greatest benefit increase an organism’s fitness, that is, its chances of survival and reproduction.
In game theory, gains depend not only on the actions of one player but also on the strategy of the opponent. This is why interactions in nature can be viewed as games with multiple participants. There are no rational solutions in the human sense, but there is evolutionary logic: strategies that increase survival are reinforced by natural selection.
Evolutionarily Stable Strategies
A key concept in evolutionary game theory is the evolutionarily stable strategy (ESS). This is a behavioral model that cannot be replaced by any other strategy. In other words, if all individuals in a population use it, alternative options do not gain any advantage.
A classic example of an ESS is the “hawk versus dove” game:
- Aggressive strategy: The hawk engages in combat for the resource.
- Passive strategy: The dove avoids conflict.
If two doves meet, the resource is divided in half. The dove always loses against the hawk. Two hawks divide the resource but suffer losses from the battle. As a result, neither a purely hawkish nor a purely dovish strategy always turns out to be an ESS. Much depends on the value of the resource and the cost of conflict. Thus, ESS demonstrates that a balance between competition and cooperation can exist in a population.
Cooperation and the Prisoners’ Dilemma
But how can we explain cooperation, which at first glance seems to contradict the idea of “survival of the fittest”? To do this, biologists use another model, the Prisoners’ Dilemma.
In this model, two players have a choice: cooperate or betray. The maximum total gain is achieved when both cooperate. But if one betrays, he gains more, and the other loses. In a one-time interaction, the rational strategy is always to betray. In nature, games are repeated many times.
In such conditions, it is advantageous to cooperate: the “tit for tat” strategy, where an individual repeats the actions of their partner, proves to be effective. If the partner cooperates, this behavior is reinforced; if they betray, they are responded to in kind. This model has shown that cooperation can be evolutionarily stable, especially in small groups where participants often meet again.
Complex Interaction Scenarios
In real life, things are even more complicated. Organisms use both pure strategies (e.g., always attack) and mixed strategies (behavior depends on circumstances). For example, small animals avoid fighting with large ones but may attack those that are weaker.
Complex models take into account:
- resource quality (valuable resources cause fierce competition);
- territoriality (fighting for breeding grounds);
- visual and acoustic signals that allow avoiding combat.
Ritualized conflicts are an example of how evolution minimizes costs. Male deer bellow and display their antlers, fiddler crabs wave their claws, and snakes make threatening movements. All of this allows the winner to be determined without a deadly fight.
Symmetric and Asymmetric Games
Types of biological interactions:
- Symmetric: in such games, the winnings are the same for both participants (for example, two identical males fighting for territory).
- Asymmetric: in these games, one of the players has an initial advantage. For example, the owner of the territory is usually willing to take greater risks than the invader.
In asymmetric games, evolution favors different strategies: strong individuals are more likely to be aggressive, while weak individuals tend to retreat.
Cooperation and Reciprocity
Interaction is not always about competition. Many systems are based on mutual exchange of benefits. Example: plants and nitrogen-fixing bacteria. The plant gives sugar, the bacteria give nitrogen. If one partner “cheats” by giving less, the other reduces its investment in response. This mechanism of reward and punishment creates conditions for sustainable cooperation.
Cooperation can be strengthened by positive feedback: the more a partner invests, the more they receive in return. This makes a strategy of honest exchange beneficial and evolutionarily stable.
The Mystery of Altruism
Altruism is behavior in which an individual sacrifices their own benefit for the benefit of another. At first glance, this seems to contradict the logic of selection, but game theory explains this phenomenon.
Altruism is based on reciprocity: today I help you, tomorrow you help me.
Examples of altruism in nature:
- Birds that give warning signals risk their own lives but save the flock.
- Vampire bats share food with hungry relatives, hoping for a return favor in the future.
Thus, altruism is beneficial in the long run. It can manifest itself in repeated interactions between the same individuals, as well as in large groups where reputation and indirect reciprocity play an important role.
Key Insights
Game theory has provided biology with a powerful tool for explaining complex interactions. It shows that competition, cooperation, and altruism are interrelated strategies that complement each other.
Game theory, when applied to biology, breaks down the simplistic image of “everyone against everyone.” It shows that evolution is a constant search for balance, where cooperation and even self-sacrifice can be beneficial strategies.