Multi-level Selection Theory
Multi-level Selection Theory explains the
evolution of altruism by
considering the action of natural selection not on an individual but on a group level.
Consider, for example, an animal population made up of warring tribes.
This would entail two levels of selection - between groups and within groups.
Within any one tribe, altruistic behaviour would be deselected
by the dominance of selfish behaviour. However, if altruistic behaviour increased
the overall fitness of the group, then the groups with the highest
proportion of altruists would outperform the more selfish ones. Under appropriate conditions,
this alternative selection pressure could dominate the disadvantage of altruism for
Multi-level selection doesn't only occur on these two levels, since animals may be a part of
various groups -
close family group, extended family, tribe etc. We can consider
evolutionary selection to happen on each level simultaneously.
This explanation of altruism finds more evidence from anthropological studies which
support viewing of groups of humans as adaptive units. According to Sober and Wilson,
"the concept of human groups as adaptive units may be supported not only by
evolutionary theory but by the bulk of empirical information
on human social groups in all cultures around the world."
Although the case for the existance of multi-level selection (MLS) is quite compelling,
this does not in itself provide evidence for MLS as an evolutionary mechanism of developing altruism,
which is only one of many behaviour patterns that
could evolve to increase the survival fitness of groups.
Multi-level selection may be supplemented or replaced by other
forms of intergroup interaction (e.g. 'Social control')
that are more evolutionarily stable. It therefore seems likely that a proper understanding of the relationship
between MLS and altruism requires consideration of other mechanisms such as
kin selection and
Francis McAndrew: (2002) New Evolutionary Perspectives on Altruism - Multilevel-Selection and Costly-Signaling Theories, Current directions in Psychological Science 11 (Issue 2) pp.79-82