Now, scientists have created a mathematical model that could explain the evolution of our personalities. The team of international scientists, led by Exeter University, designed the model by examining social behaviour in a range of different species.
For some time, biologists have used the 'theory of kin selection' to explain why some animals adopt altruistic behaviour at their own expense.
For example, worker bees will sacrifice their lives to promote the welfare of their mother - the Queen bee.
However, this theory has not been able to explain the role of genetic polymorphism, which promotes diversity within a population.
It also does not explain why some individuals appear to be genetically programmed to help others while living side-by-side with others who tend to exploit their generosity.
The researchers used microbes that live in colonies, such as yeast, as inspiration to explore why some individuals are more generous than others.
They found that the behaviour of individuals can often evolve to be determined by a set of inherited genetic tendencies.
For example, their behaviour might be predicted by their relation to other members of their community, and their surroundings rather than in direct response to what they sense or experience.
Dr Sasha Dall, a co-author on the paper told MailOnline: 'This means that the amount that individuals invest in a “public good” (a resource that is available to all individuals in an area) is strictly genetically determined (i.e. is not affected by experience).'
He added: 'As humans, our behaviours are flexible and we base what we are meant to do on what we see after processing information about our world.
'However, some species rely on inherited instructions on what to do - individuals behave differently according to which specific genetic variants they are born with.
'What we have been able to show is how you can get a situation where you end up with distinct levels of genetically determined niceness coexisting within populations.'
While this model has currently only been applied to microbial systems like yeast, Dr Hall said: 'The general results should apply to any social species, including humans.'