Altruism in animals

Altruism is a well-documented animal behaviour, which appears most obviously in kin relationships but may also be evident amongst wider social groups, in which an animal sacrifices its own well-being for the benefit of another animal.

Overview

In the science of ethology (the study of behavior), and more generally in the study of social evolution, on occasion, some animals do behave in ways that reduce their individual fitness but increase the fitness of other individuals in the population; this is a functional definition of altruism.^[1] Research in evolutionary theory has been applied to social behaviour, including altruism. Cases of animals helping individuals to whom they are closely related can be explained by kin selection, and are not considered true altruism. Beyond the physical exertions that mothers, and in some species fathers, undertake to protect their young, extreme examples of sacrifice may occur. One example is matriphagy (the consumption of the mother by her offspring) in the spider Stegodyphus. Hamilton's rule describes the benefit of such altruism in terms of Wright's coefficient of relationship to the beneficiary and the benefit granted to the beneficiary minus the cost to the sacrificer. Should this sum be greater than zero a fitness gain will result from the sacrifice.

When apparent altruism is not between kin, it may be based on reciprocity. A monkey will present its back to another monkey, who will pick out parasites; after a time the roles will be reversed. Such reciprocity will pay off, in evolutionary terms, as long as the costs of helping are less than the benefits of being helped and as long as animals will not gain in the long run by "cheating" – that is to say, by receiving favours without returning them. This is elaborated on in evolutionary game theory and specifically the prisoner's dilemma as social theory.

Implications in evolutionary theory

Researchers on alleged altruist behaviours among animals have been ideologically opposed to the social darwinist concept of the "survival of the fittest", under the name of "survival of the nicest" — the latter being globally compatible, however, with the theory of evolution by natural selection. Insistence on such cooperative behaviours between animals was first exposed by the Russian zoologist and anarchist Peter Kropotkin in his 1902 book, Mutual Aid: A Factor of Evolution.

Recent developments in game theory have provided some explanations for apparent altruism, as have traditional evolutionary analyses. Among the proposed mechanisms are:

• Behavioural manipulation (for example, by certain parasites that can alter the behavior of the host)
• Bounded rationality (for example, Herbert Simon)
• Kin selection including eusociality (see also "The Selfish Gene")
• Memes (by influencing behavior to favor their own spread; see religion as a meme)
• Reciprocal altruism, mutual aid
• Sexual selection, in particular, the Handicap principle
• Reciprocity
  • Indirect reciprocity (for example, reputation)
  • Strong reciprocity^[2]
• Pseudo-reciprocity

The study of altruism was the initial impetus behind George R. Price's development of the Price equation which is a mathematical equation used to study genetic evolution. An interesting example of altruism is found in the cellular slime moulds, such as Dictyostelium mucoroides. These protists live as individual amoebae until starved, at which point they aggregate and form a multicellular fruiting body in which some cells sacrifice themselves to promote the survival of other cells in the fruiting body. Social behavior and altruism share many similarities to the interactions between the many parts (cells, genes) of an organism, but are distinguished by the ability of each individual to reproduce indefinitely without an absolute requirement for its neighbors.

Jorge Moll and Jordan Grafman, neuroscientists at the National Institutes of Health and LABS-D'Or Hospital Network (J.M.) provided the first evidence for the neural bases of altruistic giving in normal healthy volunteers, using functional magnetic resonance imaging. In their research, published in the Proceedings of the National Academy of Sciences USA in October, 2006,^[3] they showed that both pure monetary rewards and charitable donations activated the mesolimbic reward pathway, a primitive part of the brain that usually lights up in response to food and sex. However, when volunteers generously placed their interests of others before their own by making charitable donations, another brain circuit was selectively activated: the subgenual cortex/septal region. These structures are intimately related to social attachment and bonding in other species. Altruism, the experiment suggested, was not a superior moral faculty that suppresses basic selfish urges but rather was basic to the brain, hard-wired and pleasurable.^[4]

A new study by Samuel Bowles at the Santa Fe Institute in New Mexico, US, is seen by some as breathing new life into the model of group selection for altruism, known as "Survival of the nicest". Bowles conducted a genetic analysis of contemporary foraging groups, including Australian aboriginals, native Siberian Inuit populations and indigenous tribal groups in Africa. It was found that hunter-gatherer bands of up to 30 individuals were considerably more closely related than was previously thought. Under these conditions, thought to be similar to those of the middle and upper Paleolithic, altruism towards other group-members would improve the overall fitness of the group.

If an individual defended the group but was killed, any genes that the individual shared with the overall group would still be passed on. Early customs such as food sharing or monogamy could have levelled out the "cost" of altruistic behaviour, in the same way that income taxes redistribute income in society. He assembled genetic, climactic, archaeological, ethnographic and experimental data to examine the cost-benefit relationship of human cooperation in ancient populations. In his model, members of a group bearing genes for altruistic behaviour pay a "tax" by limiting their reproductive opportunities to benefit from sharing food and information, thereby increasing the average fitness of the group as well as their inter-relatedness. Bands of altruistic humans would then act together to gain resources from other groups at this challenging time in history.^[5]

Altruist theories in evolutionary biology were contested by Amotz Zahavi, the inventor of the signalling theory and its correlative, the handicap principle, based mainly on his observations of the Arabian Babbler, a bird commonly known for its surprising (alleged) altruistic behaviours.

Examples of animal altruism

• Dogs often adopt orphaned cats, squirrels, ducks and even tigers.^[6]
• Dolphins support sick or injured animals, swimming under them for hours at a time and pushing them to the surface so they can breathe.^[7]
• Wolves and wild dogs bring meat back to members of the pack not present at the kill.^{[citation needed]}
• Male baboons threaten predators and cover the rear as the troop retreats.^{[citation needed]}
• Gibbons and chimpanzees with food will, in response to a gesture, share their food with others of the group.^{[citation needed]} Chimpanzees will help humans and conspecifics without any reward in return.^[8]
• Bonobos have been observed aiding injured or handicapped bonobos.^[9]
• Vampire bats commonly regurgitate blood to share with unlucky or sick roost mates that have been unable to find a meal, often forming a buddy system.^[10][11]
• Raccoons inform conspecifics about feeding grounds by droppings left on commonly shared latrines. A similar information system has been observed to be used by common ravens.^[12]
• In numerous bird species, a breeding pair receives support in raising its young from other "helper" birds, including help with the feeding of its fledglings.^[13] Some will even go as far as protecting an unrelated bird's young from predators ^[14]
• Most mammal carnivores like wolves or dogs have a habit of not harming pack members below certain age, of opposite sex or in surrendering position (in case of some animals, the behavior exists within entire species rather than one pack).^{[citation needed]}
• Vervet Monkeys give alarm calls to warn fellow monkeys of the presence of predators, even though in doing so they attract attention to themselves, increasing their personal chance of being attacked.^[15]
• Walruses have been seen adopting orphans who lost their parents to predators.^[16]
• Some termites and ants release a sticky secretion by fatally rupturing a specialized gland. This autothysis altruistically aids the colony at the expense of the individual insect. For example, defending against invading ants by creating a tar baby effect.^[17]
• Meerkats often have one standing guard to warn whilst the rest feed in case of predators attack.
• African buffalo will rescue a member of the herd captured by predators.
• Lemurs of all ages and of both sexes will take care of infants unrelated to them

See also

• Cheating (biology)
• Evolutionarily stable strategy
• Gene-centered view of evolution
• Sociobiology
• Evolution of morality
• Evolutionary ethics

References

1. ^ Robert L. Trivers (1971). "The Evolution of Reciprocal Altruism". The Quarterly Review of Biology 46 (1): 35. doi:10.1086/406755. http://scholar.google.se/scholar?cluster=17273593725342277972&hl=sv&as_sdt=2000. 
2. ^ Herbert Gintis (September 2000). "Strong Reciprocity and Human Sociality". Journal of Theoretical Biology 206 (2): 169–179. doi:10.1006/jtbi.2000.2111. PMID 10966755. 
3. ^ Human fronto–mesolimbic networks guide decisions about charitable donation, PNAS 2006:103(42);15623-15628)
4. ^ Vedantam, Shankar (May 2007). "If It Feels Good to Be Good, It Might Be Only Natural". Washington Post. http://www.washingtonpost.com/wp-dyn/content/article/2007/05/27/AR2007052701056.html. Retrieved April 23, 2010. 
5. ^ Fisher, Richard (07 December 2006) "Why altruism paid off for our ancestors" (NewScientist.com news service) [1]
6. ^ Mutt-ernal Instincts - Dachshund adopts kitties, Pitbull adopts kitties, Border Collie adopts... tigers? - 2006-09-29
7. ^ Davidson College, biology department (2001) Bottlenose Dolphins - Altruism, article retrieved March 11, 2009.
8. ^ Human-like Altruism Shown In Chimpanzees
9. ^ October 7, 2005, Hour Two:
10. ^ de Waal, Frans (1996). Good Natured. Harvard University Press. pp. 20–21. ISBN 0-674-35660-8. 
11. ^ Perry, Julie (April 19, 2002). "Reciprocal Altruism in Vampire Bats". http://www.bio.davidson.edu/people/vecase/behavior/Spring2002/Perry/altruism.html. Retrieved October 10, 2009. 
12. ^ Hohmann, Ulf; Bartussek, Ingo; Böer, Bernhard (2001) (in German). Der Waschbär. Reutlingen, Germany: Oertel+Spörer. ISBN 978-3886273010. 
13. ^ Brown, David (August 17, 2007). "Birds' Cooperative Breeding Sheds Light on Altruism". The Washington Post. http://www.washingtonpost.com/wp-dyn/content/article/2007/08/16/AR2007081602257.html. Retrieved April 23, 2010. 
14. ^ Fackelmann, Kathy A. (1989). "Avian altruism: African birds sacrifice self-interest to help their kin - white-fronted bee eaters". Science News. http://findarticles.com/p/articles/mi_m1200/is_n23_v135/ai_7680117. 
15. ^ Cheney, D. L. & Seyfarth, R. M. (1990). How monkeys see the world: Inside the mind of another species. University of Chicago Press. ISBN 9780226102467. http://books.google.com/?id=QbWTd85eHUgC. 
16. ^ "Walrus: Odobenidae - Behavior And Reproduction". http://animals.jrank.org/pages/3099/Walrus-Odobenidae-BEHAVIOR-REPRODUCTION.html. Retrieved 2008-08-12. 
17. ^ Bordereau, C., Robert, A., Van Tuyen V. & A. Peppuy (1997). "Suicidal defensive behavior by frontal gland dehiscence in Globitermes sulphureus Haviland soldiers (Isoptera)". Insectes Sociaux 44 (3): 289–297. doi:10.1007/s000400050049. 

External links

• Biological Altruism
• International Union for the Study of Social Insects
• Quick Guide: Kin Selection (Current Biology)
• Quick Guide: Altruism (Current Biology)
• "Mutt-ernal Instincts" An article about dogs caring for other species' young (cats, tigers, etc.).