What is the Difference Between Kin Selection and Reciprocal Altruism

The main difference between kin selection and reciprocal altruism is that kin selection favors the reproductive success of the other relatives even at a cost to the organism’s own survival and reproduction. Whereas, in reciprocal altruism, an organism reduces its own fitness by increasing the fitness of another organism. Furthermore, kin selection uses shared genes, while reciprocal altruism does not use shared genes.  

Kin selection and reciprocal altruism are two altruistic strategies, which describe the mechanisms of increasing the evolutionary fitness of an organism by decreasing the fitness of the actor. However, kin selection is irreversible while reciprocal altruism is reversible. 

Key Areas Covered 

1. What is Kin Selection
     – Definition, Characteristics, Importance
2. What is Reciprocal Altruism
     – Definition, Characteristics, Importance
3. What are the Similarities Between Kin Selection and Reciprocal Altruism
     – Outline of Common Features
4. What is the Difference Between Kin Selection and Reciprocal Altruism
     – Comparison of Key Differences

Key Terms 

Altruism, Kin Selection, Reciprocal Altruism, Reproductive Success, Speciation

What is Kin Selection 

Kin selection is the type of obligate altruism in which the actor organism endures the permanent loss of direct fitness. Also, it is the most obvious type of altruism, occurring through changing the evolutionary fitness at the gene-level by altering the gene frequencies. Generally, this occurs through allowing the individual to increase the success of its genes by helping relatives that share those genes. More importantly, kin selection is the type of natural selection responsible for increasing the reproductive success of a particular group of organisms.

Figure 1: The Co-Operative Behaviour of Social Insects Like the Honey Bee Can be Explained by Kin Selection.

Let’s look at an example; the occurrence of sterile in social insects, such as honey bees is one of the key examples of kin selection. These insects leave reproduction to their mothers while their workers would forage for the colony. Thus, this argues that kin selection benefits the related organisms within the same stock. Explaining further, it allows the evolution of a trait, and thus, conferring benefits to a particular organism, but destroying the reproductive success of another. 

What is Reciprocal Altruism 

In contrast to kin selection, reciprocal altruism is the type of facultative altruism in which the actor organism encounters only a temporarily loss of direct fitness. That means; the lost fitness can be regained following the reproduction. Therefore, it is a type of reversible altruism. Besides, reciprocal altruism is a type of cooperative behavior among closely related organisms. Hence, it becomes a form of competitive altruism, which is performed unconditionally. Still, the actor organism expects that the other organism will act in a similar manner at a later time. 

Figure 2: Arctic Terns Protect Their Offspring Extremely Aggressively by Very Quick Drop-Downs from a Stationary Flight over Their Enemies.

Let’s look at an example now; one of the most precise examples of reciprocal altruism is protecting the nests of the neighbors by the red-winged blackbird males. Here, the neighboring nests may contain extra-pairs of offsprings with some of the male bird’s DNA. Therefore, they only protect the nests of other closely related males.

Furthermore, the warning calls in birds is another example of reciprocal altruism. Although these warning calls expose the birds, and thus, putting them in danger, they prevent the pray from getting experienced on the localization of specific individuals as well as on hunting techniques. Thus, in general, reciprocal altruism permits organisms to defend their relatives from predators or nutrient deficiency.  

Similarities Between Kin Selection and Reciprocal Altruism  

• Kin selection and reciprocal altruism are two strategies, which describe the mechanisms of increasing evolutionary fitness among genetically related organisms.  
• Generally, they increase the evolutionary fitness of a second organism at the expense of the first organism.  
• Therefore, the two agents that are undergoing these strategies would cooperate unconditionally in the first period and either undergo naturals selection or behave cooperatively (altruistically) as long as the other agent does as well.   

Difference Between Kin Selection and Reciprocal Altruism 

Definition 

Kin selection refers to the natural selection in which an apparently disadvantageous characteristic (especially altruistic behavior) increases in the population due to increased survival of individuals genetically related to those possessing the characteristic. Meanwhile, reciprocal altruism refers to a behavior whereby an organism acts in a manner that temporarily reduces its fitness while increasing another organism’s fitness with the expectation that the other organism will act in a similar manner at a later time.  

Introduced by 

The kin selection was first introduced by Charles Darwin in his book ‘On the Origin of Species’ in 1859, while the concept of reciprocal altruism was first developed by Robert Trivers to explain the evolution of cooperation as instances of mutually altruistic acts.  

Mechanism of Altruism 

Kin selection favors the reproductive success of the other relatives even at a cost to the organism’s own survival and reproduction while, in reciprocal altruism, an organism reduces its own fitness by increasing the fitness of another organism.  

Significance 

Kin selection is the most obvious type of altruism, while reciprocal altruism only temporarily reduces the fitness of the actor. 

Type of Altruism 

Kin selection is the type of obligate altruism, while reciprocal altruism is the type of facultative altruism.  

Type of Organisms 

Kin selection mainly evolves among relatives of a particular population, while reciprocal altruism can evolve among closely related organisms on an individual basis. 

Involvement of Mating 

The kin selection proceeds through mating, while reciprocal altruism does not proceed through mating. 

Involvement of Genes 

Kin selection uses shared genes while reciprocal altruism does not use shared genes. 

Effect on Gene Frequencies 

The kin selection causes an increase in gene frequencies while reciprocal altruism does not cause an increase in gene frequencies. 

Undergoing Natural Selection 

Kin selection is a type of natural selection for reproductive success while reciprocal altruism is a cooperative behavior of defending or supplying nutrients. 

Reversibility 

Kin selection is irreversible while reciprocal altruism is reversible. 

Contribution to Speciation 

Kin selection contributes to speciation while reciprocal altruism does not contribute to speciation. 

Contribution to evolution 

Kin selection contributes to evolution, while reciprocal altruism does not contribute to evolution.  

Examples 

Origin of sterile, social insects such as honey bees is an example of kin selection while nest protecting of neighbors by the red-winged blackbird males is an example of reciprocal altruism. 

Conclusion 

Kin selection is a type of natural selection, increasing the reproductive success of an organism through altruistic behavior. Therefore, it occurs among genetically related organisms. On the other hand, the reproductive success of the organism is increased through increasing gene frequencies. Hence, kin selection leads to the origin of species, contributing to evolution. Usually, the occurrence of sterile in social insects such as honey bees is an example of kin selection. In comparison, reciprocal altruism is a cooperative behavior, increasing the evolutionary fitness of a second organism that is closely related to the first. Basically, it is a type of behavior, and there is no change in gene frequencies of none of the types of organisms in the process. So, it does not lead to speciation or does not contribute to evolution. Therefore, the main difference between kin selection and reciprocal altruism is the type of altruism. 

References:

1. Allen-Arave, Wesley, et al. “Reciprocal Altruism, Rather than Kin Selection, Maintains Nepotistic Food Transfers on an Ache Reservation.” Evolution and Human Behavior, vol. 29, no. 5, 2008, pp. 305–318., doi:10.1016/j.evolhumbehav.2008.03.002.
2. Ale, Som B et al. “Evolution of cooperation: combining kin selection and reciprocal altruism into matrix games with social dilemmas.” PloS one vol. 8,5 e63761. 22 May. 2013, doi:10.1371/journal.pone.0063761.
3. “Kin Selection.” Wikipedia, Wikimedia Foundation, 14 Dec. 2019, Available Here.
4. “Reciprocal Altruism.” Wikipedia, Wikimedia Foundation, 17 Nov. 2019, Available Here.

Image Courtesy:

1. “Todd Huffman – Lattice (by)” By Todd Huffman from Phoenix, AZ – Lattice (CC BY 2.0) via Commons Wikimedia 
2. “Arctic tern (Sterna paradisaea) attacking, Amsterdam island, Svalbard” By AWeith – Own work (CC BY-SA 4.0) via Commons Wikimedia   

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