Biology Reference
In-Depth Information
CHAPTER 11
Social Behaviours:
Altruism to Spite
Photo © David Pfennig
So far throughout this topic we have championed the view that natural selection
designs individuals to behave in their own selfish interests and not for the good of their
species or for the good of the group in which they live. For example, observed clutch
size, foraging behaviour and mating patterns are what would be expected if
selection optimized behaviour and life history strategies to maximize an individual's
reproductive success.
However, it will be obvious to any naturalist that animals do not behave selfishly all
the time. Often individuals apparently cooperate with others. Several lions may
cooperate to hunt prey; in many species of birds and mammals individuals give alarm
calls to warn others of the approach of a predator; in many cooperative breeding
species, such as meerkats, an individual may help others to produce offspring rather
than have young itself. In some cases, cooperation provides an immediate or delayed
benefit to the survival or reproduction of the actor, that outweighs the cost of performing
the behaviour. For example, one individual may help another because that individual
will then help it back. In this case, cooperation is mutually beneficial and can be
explained by selfish interests, as is discussed in further detail in the next chapter.
In other cases, and more troubling for evolutionary theory, cooperative behaviours
provide no benefit to the actor and are altruistic. Specifically, a behaviour is defined as
altruistic if it is costly to the personal reproduction of the actor who performs that
behaviour, but beneficial to another individual or individuals (Box 11.1). For example,
in the social insects, the ants, bees, wasps and termites, the workers are often sterile,
giving up any opportunity to reproduce, in order to help raise the offspring of the queen.
If natural selection favours individuals that behave in their own selfish interests, how
can we explain such altruistic helping behaviours?
To understand how natural selection can lead to altruistic, and even spiteful
behaviours, we have to return to the fundamental issue of exactly how natural selection
works at the genetic level.
Mutual benefit:
benefit to others,
benefit to actor
Altruism: benefit
to others, cost to
actor
