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Altruism refers to behaviors that are beneficial to others at a cost to oneself, often involving self-sacrifice or the provisioning of resources to others without expectation of repayment. These actions can be carried out at various levels of intensity, from minor acts of kindness to major sacrifices for the benefit of others. Humans are an intensely social species, frequently performing altruistic behaviors that benefit others. Understanding the evolutionary origins of altruism has long been a subject of interest and research across multiple disciplines, including psychology, biology, and anthropology. This article reviews the main theories that have been proposed to explain the evolutionary mechanisms behind altruism in humans.

Evolutionary Theories of Altruism

Several evolutionary theories have been proposed to explain the existence and persistence of altruistic behavior in humans:

Kin Selection

Kin selection theory posits that individuals are more likely to act altruistically towards others if they share a greater proportion of their genetic material with them. This theory, first introduced by biologist J.B.S. Haldane, suggests that altruistic behaviors that increase the survival and reproductive success of relatives can indirectly increase one's own fitness through the shared genes maneuvered between them. Harvard biologist E. O. Wilson further advanced the kin selection theory to include the concept of inclusive fitness, where the fitness of an individual is measured not only by their own reproductive success but also by the success of their relatives ([1]).

Reciprocal Altruism

Reciprocal altruism, proposed by Robert Trivers, involves the exchange of altruistic acts between individuals with the expectation that the favors will be returned in the future. This theory posits that individuals engage in altruistic behaviors to build social relationships and gain indirect benefits, such as increased social status, opportunities for cooperation, or the ability to receive help when needed. Reciprocal altruism can occur within and outside of kin relationships, and its success depends on individuals' ability to recognize and remember those who have helped them in the past ([2]).

Indirect Reciprocity

Indirect reciprocity is a form of reciprocal altruism in which individuals benefit from their altruistic actions through third-party observers rather than a direct exchange with the recipient of the altruistic behavior. This theory, initially proposed by Richard D. Alexander, posits that individuals who engage in altruism may acquire positive reputations and receive help from others who have observed their altruistic acts. Indirect reciprocity can contribute to the establishment and maintenance of cooperative behavior in larger, more complex social groups ([3]).

Group Selection

Group selection is a controversial evolutionary theory suggesting that altruistic behaviors can evolve if they promote the survival and reproductive success of groups rather than individuals. Under this framework, groups or populations that are composed of a high proportion of altruistic individuals may have an advantage in overcoming environmental challenges or competing with other groups, thereby promoting the persistence of altruistic behaviors through the benefits they bring to the collective. This theory has gained less support in recent years due to the difficulty of demonstrating group-level benefits balancing the individual cost of altruism ([4]).

Factors Influencing Altruism

Some factors have been shown to influence the likelihood of individuals engaging in altruistic behaviors. These include:

  • Genetic factors: Evidence of a genetic basis for altruism comes from twin studies, animal research, and molecular genetics studies. These findings suggest that individual differences in altruistic tendencies may be partly influenced by genetic factors, although the specific underlying mechanisms are still largely unknown ([5]).
  • Social norms: Cultural norms and societal values can shape individuals' altruistic behaviors, with some societies emphasizing altruism and cooperation more than others. Social norms can affect altruism through mechanisms such as social learning, imitation, and conformity.
  • Personal relationships: The strength and nature of relationships can have a significant impact on altruistic behaviors. Individuals are more likely to engage in altruistic acts for close friends and family members, reflecting the influence of kin selection in shaping our altruistic tendencies.
  • Cognitive abilities: Higher cognitive capacities, such as empathy, perspective taking, and theory of mind, have been linked to increased altruistic behaviors in humans. These cognitive abilities allow individuals to understand and respond to the needs of others, facilitating the development and expression of altruistic behaviors ([6]).


Altruism is a complex and multifaceted aspect of human behavior that has evolved through a variety of evolutionary mechanisms, including kin selection, reciprocal altruism, indirect reciprocity, and possibly group selection. Factors such as genetic predispositions, social norms, personal relationships, and cognitive abilities all play a role in shaping our altruistic tendencies. The evolutionary psychology of altruism sheds light on the intricate social nature of Homo sapiens and provides a framework for understanding the emergence of cooperation and prosocial behaviors in our species.