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Despite years of research suggesting otherwise, a new study claims humans did not evolve to cooperate with one another as strongly as first thought.

Previous theories claim that in nature, humans cooperate because it in everyone's interest to do so.

But, given half the chance, people have a tendency to be selfish - especially if they can increase the amount they benefit from betraying or deceiving someone. 

Two University of Pennsylvania researchers studied human cooperation. Their study focused on a game theory called the Prisoner's Dilemma, in which people are more likely to benefit if they were selfish (stock image shown) instead of cooperating

The latest study, published in the Proceedings of the National Academy of Sciences, was carried out by scientists from the University of Pennsylvania. 

In a series of experiments twisting the classical game theory match-up known as the Prisoner's Dilemma, selfish strategies became more successful.

In the classic game, if both players cooperate, they both receive an equal payoff.

But if one cooperates and the other does not, the cooperating player receives the smallest possible payoff, and the defecting player the largest.

If both players do not cooperate, they both receive a payoff, but it is less than what they would gain if both had cooperated.

In general it pays to cooperate, but it can pay even more to be selfish.

Last year, postdoctoral researcher Alexander Stewart and Proffesor Joshua Plotkin from the University of Pennsylvania published a mathematical explanation for why cooperation and generosity have evolved in nature.

But their new research played out in a large, evolving population, found that adding more flexibility to the game can allow selfish strategies to be more successful.

In the new investigation, the researchers added a twist. 

Not only could players alter their strategy - whether or not they cooperate - but they could also vary the payoffs they received for cooperating.

Initially, as in their earlier study, cooperative strategies found success.

But with higher and higher payoffs at stake, the temptation to defect also rose.

And they found that the population of players reached a tipping point, after which defection was the predominant strategy in the population.

The work paints a dimmer but more realistic view of how cooperation and selfishness balance one another in nature.

'It's a somewhat depressing evolutionary outcome, but it makes intuitive sense,' said Proffesor Plotkin.

'We had a nice picture of how evolution can promote cooperation even among self-interested agents and indeed it sometimes can, but, when we allow mutations that change the nature of the game, there is a runaway evolutionary process, and suddenly defection becomes the more robust outcome.'

Previous studies found people are more likely to cooperate (stock image shown) more than not, but the latest research revealed that by increasing the reward for betrayal, people became more selfish. This suggests humans are not naturally wired to cooperate with each other