In the past it was taken as a given that while humans were capable of demonstrating selfish and altruistic behaviour, animals always acted for the good of their species. This article explores animals’ tendencies towards these same behaviours and the reasons behind them.
For the individual deciding how to behave, is it best to benefit the species or does selection act on individuals to essentially act ‘selfishly’ (this term does not imply malice or forethought). Up until the early 1960’s it was common for biologists to think of animals acting for the good of the species. V.C. Wynne Edwards put this into print in 1962 in a book called ‘Animal Dispersion in Relation to social Behaviour’. Wynne Edwards argued that animals acted for the good of the species. He would argue for example, that individuals could assess the available resources and limit the number of offspring to address the balance, so that a species would not outgrow resources. Other ideas included the argument that animals do not fight a lot because it would harm other group members. These ideas were part of ‘biological thought’ at the time.
However, putting these ideas down on paper made them open to deeper analysis and the whole idea was toppled by one further point. In 1964 William Hamilton argued that if one selfish individual was created through mutation the situation could be very different. If all the individuals within a species were willing to limit the number of offspring maintain a balance with available resources, then the selfish individual would simply have as many offspring as possible. There would be a lot of offspring and offspring would be likely to be selfish and so they would do the same. It would not take very many generations for the species to eventually be one made up of individuals that prioritised their own survival over that of the whole species.
One example of behaviour that does not support a ‘good of the species’ theory occurs when male lions take over a pride. When males take over a pride they kill any cubs they find. This is obviously to the advantage of the new male lions as it will make the females receptive and mating can ensue. Time is of the essence because any young born need to grow before the pride is taken over again whereby the new young would be vulnerable to the new pride leaders. In this case the benefits are on the side of the males and obviously not the other individuals involved.
William Hamilton took the explanation further. Any explanation needed to include the examples in nature that seem to be selfless acts for the sake of others. In other words why would an animal reduce its own fitness (by reducing its reproductive success via time or in whatever form) to benefit another animal? How do you explain the fact that bee-eaters will help other bee-eaters feed their young?
On further analysis, animals that help other animals are usually related to them. When bee-eaters (a kind of bird) help others to feed their young, they are usually helping their parents raise a sibling. This is similar for many examples with varying degrees of effort and ‘relatedness’. Hamilton then extended the idea of fitness to go beyond the individual and refer to the genes within the individual. The term used is inclusive fitness.
An animal can benefit its own inclusive fitness by helping a sibling to be raised. This is one way that it can maximise the amount of its own genetic makeup entering the next generation. A sibling contains 50% of an individual’s genetic composition. So by helping to raise a sibling before it reproduces itself, an animal will help to get more of its own genes passed on. It will increase it’s ‘inclusive fitness’.
Altruism towards non-kin
In many group living animals there exists a level of apparent altruism between individuals that do not share a close family bond. One form of this is called mutualism. Mutualism (once referred to as symbiosis) occurs when individuals from separate species interact with each other for the benefit of them both. A good example is termites and the specialised protozoa that inhabit their guts. The termites cannot digest cellulose but the protozoa can and consequently release sugars that the termites can then absorb. The protozoa get free food and shelter. Another way in which non-kin can exhibit altruism towards each other is when they use reciprocal altruism whereby they develop tit for tat relationships.
Altruism amongst non-kin is explained by analysing the advantages and disadvantages of co-operation. In certain groups, in certain situations, cooperation between none relatives would be the best way of acting in order to maximise survival and fitness.
This article has been put together by the distance learning organisation Start Learning who are experts in home study.
If you want to find out more about Advanced Animal Behaviour or many other distance learning courses please browse their website: http://www.start-learning.co.uk
Kerrana McAvoy
Academic Director – Start Learning
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