The Evolution of Helping in Nature

You would share a cookie, but why would a meerkat?

Contributed by Jessica Etienne, Kavya Reddy, Madison Malone, Okeoghene Ogaga

Evolution, the inherited change in a group of organisms over time, is often misunderstood. One major misconception is that evolution leads to immoral behavior. However, many animals, insects and plants have evolved altruistic behavior, an interaction between two individuals in which one individual reduces its own fitness (the ability of an individual to survive and reproduce) for the benefit of another. In other words, the individual is doing something good for someone else. Altruism is important evolutionarily because it interacts with natural selection by promoting cooperation of a group as a method of competition against others. Altruism can come in two forms: either an organism performs an action without anything in return or an organism becomes less competitive with other individuals without receiving any benefits. It seems counter intuitive for organisms in nature to perform a selfless action, however a chimpanzee will help another without receiving anything in return. One idea as to why this happens is that it has evolved due to indirect fitness. The total fitness of an individual includes indirect and direct fitness; indirect fitness is benefit for oneself gained through the fitness of others, while direct fitness is the benefit gained directly from one’s own actions. Contrary to what many believe, the fittest individuals are the ones that manage to spread their genes the most because fitness incorporates more than an individual’s physical capabilities.

Typically within a population, organisms tend to help those that are related to them rather than strangers; for example, plants will compete less for resources when they are next to their relatives than when they are next to strangers. This is most likely because individuals that are related to one another share a percentage of DNA. A unit for expressing this percentage is called coefficient of relatedness (r). One can model the likelihood of altruistic behavior using relatedness and Hamilton’s Rule, which states that the coefficient of relatedness, multiplied by the benefit (b) that the related individual receives, should be greater than the cost (c) that the individual performing the action experiences:  rb-c>0  or rb>c

Despite the accuracy of Hamilton’s Rule in predicting the evolution of altruistic behavior, it is important to remember that it a model that describes why altruism occurs, and is still being investigated. For more on Hamilton’s rule, see the video below.

In order for organisms to show altruism preferentially towards related individuals, they need to be able to know who they are related to; organisms do this two different ways, either using kin recognition (they can recognize who their brothers are) or kin fidelity (families stay together).

In addition, altruistic behavior does not imply that an individual will sacrifice itself for the “good of the species,” but rather Individuals are sacrificing themselves to increase the fitness of their relatives, and therefore increase their own fitness indirectly.

For more information, go to:

Abbot, P., Abe, J., Alcock, J., Alizon, S., Alpedrinha, J. A. C., Andersson, M., Andre, J.-B., et al. (2011). Inclusive fitness theory and eusociality. Nature, 471(7339), E1–E4. doi:10.1038/nature09831

Curry, O., Roberts, S. G. B. and Dunbar, R. I. M. (2013), Altruism in social networks: Evidence for a ‘kinship premium’. British Journal of Psychology, 104: 283–295. doi: 10.1111/j.2044-8295.2012.02119.x

Dudley, S., Murphy, G., and File, A. 2013. Kin recognition and competition in plants. Functional Ecology 27(4) 898-906. DOI: 10.1111/1365-2435.12121

Ratnieks, F. and Wenseleers, T. 2008. Altruism in insect societies and beyond: voluntary or enforced? Trends in Ecology and Evolution 23(1) 45-52. doi:10.1016/j.tree.2007.09.013

Yamamoto, S., Humle, T., and Tanaka, M. 2012. Chimpanzees’ flexible targeted helping based on an understanding of conspecifics’ goals PNAS 109 (9) 3588-3592. doi:10.1073/pnas.1108517109