Theory of Mind.
The ability to put yourself in anothers place mentally understand the motivations and beliefs and enables us to see things from their viewpoint.

Chandler et al conducted a study on children as young as 2 and concluded that even this young age can understand and carry out 'theory of mind'.

For Reciprocal Altruism to be affective Theory of Mind is necessary for this skill as altruism depends on being able to detect reciprocation.

Behavioural characteristics e.g. successful defence of territory from predators also afford an advantage.

Natural Selection.
Natural selection is a key term in Darwin's Evolutionary theory and is processed by which genes carry advantageous adaptive value -characteristics are passed on.

Darwin's finch studies revealed different beak shapes afforded a survival advantage when insects were main source of food. In different environments different beaks evolved which were fitter for the environment.

Reciprocal Altruism.
An Evolutionary psychological term to explain the evolution of the behaviour of benefitting others who are not kin and where the altruist benefits directly.

Sexual Selection.
A form of natural selection, physical characteristics affects access to mates, this effects amount of offspring for males, a higher quality of mate will effect viability of offspring and increased chance of gene transmission.