Altruism, fitness, and the impact on the individual vs. the species

Updated: Oct 19, 2019

Altruism is defined as a selfless act, that benefits another at the individual’s expense (Okasha, 2013). Human altruism is deemed unique in the animal world, and because gene-based evolutionary theories cannot explain patterns of human altruism, academics tend to  point to social pressures and the ‘moral compass’ of people to explain it (Fehr and Fischbacher 2003).

Why in that case, do some animals consistently demonstrate altruistic behaviours? Some examples include cooperative breeding, reciprocal altruism, reproductive altruism and arguably, kin relationships.

Kin relationships is a relatively simple one to explain; a mother or biological parents will put energy and time into rearing offspring to give their genes the greatest chance of being passed on with future generations.

Cooperative breeding, as seen in many bird species, has conspecifics caring for the young of the group and not necessarily or exclusively their own young (Hatchwell and Komdeur, 2000). While we can argue that parental care isn’t necessarily altruistic, as there is a genetic benefit to the individual, caring for the offspring of others, despite being conspecifics, doesn’t benefit the individual in the same way. However, if all the members of the group care for all the young, then the survival of the individual’s offspring is still being cared for and increased.

This explains this behaviour as not entirely altruistic, as there is a benefit for the individual.

Common vampire bats (Desmodus rotundus) demonstrate reciprocal altruism in the form of food sharing. The bats will leave their hides during the night to find food to feed on for a blood meal. Without feeding for two nights, the bat will starve. There is a system among this species that means if a bat has not fed, a neighbour will regurgitate some of their feed, sacrificing their own nutrition with the hope that the starving bat will return the favour if required in the future, hence reciprocal (Wilkinson, 1990). This is an act that involves a massive survival risk to the individual, but with the reciprocation, cannot be classed as true altruism.

In the case of the naked mole rat (Heterocephalus glaber), the demonstrate reproductive altruism. The term eusociality is used to describe these mammals, which includes cooperative brood care, and reproductive and non-reproductive individuals within a colony, a trait shared with honey bees (Burda, et al, 2000). For the individuals that cannot reproduce, they are putting energy into rearing offspring or providing an increased fitness for members of the colony which do not support it’s own genetic survival, so at a glance appears to be a truly altruistic act.

I will continue to argue however, that because all of the examples above (including the eusociality of some species) contribute a benefit to the species, even not specifically for an individual, there is an evolutionary benefit which allowed the continuance of a species. I therefore argue that there is no truly altruistic act, even if the reproductive or social systems of a group of animals reduce the fitness of the individual, the fitness of the species will always increase.


H., Honeycutt, B. L., Begall, S., Locker-Grutjen, O. and Scharff, A. (2000) Are naked and common mole rats eusocial and if so, why? Behavioural Ecology and socio-biology, 47, 293. Available online at: [Accessed: 18th November 2016]

Fehr E. and Fischbacher, U. (2003) The Nature of Human Altruism. Nature, 425, 785-791. Available online: [Accessed: 18th November 2016]

Hatchwell, B. J. and Komdeur, J. (2000) Ecological constraints, life history traits and the evolution of cooperative breeding. Animal Behaviour, 59, 6, 1079-1086. Available online: [Accessed: 18th November 2016]

Okasha, S. (2013) Biological Altruism. Stanford Encyclopaedia of Philosophy. Available online: [Accessed: 18th November 2016]

Wilkinson, G. S. (1990). Food Sharing in Vampire Bats. Ethology and Socio-biology, 9, 85-100. Available online: [Accessed: 18th November 2016]

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