It's often said that most women prefer the scrappy male over the nice guy. But have you ever wondered what makes some men more aggressive? Well, it is the fair sex, along with property.

A new study of the mathematics of warfare has revealed that the lust for women and the hunger to acquire property are the two primary reasons for the evolution of belligerence and bravery in men.

In fact, an international team has based its findings on an analysis of the evolutionary forces that shaped the need for males to be belligerent, which raises their probability of trying to conquer neighbours, and of bravery, which increases the probability of succeeding in conquest.

The mathematical analysis of the evolution war by the team, led by Laurent Lehmann and Prof Marc Feldman of Stanford University, focused on small-scale, pre-state societies, for instance hunter-gatherers societies, British newspaper The Daily Telegraph reported.

The study has shown that the "selective pressure" on genes linked with belligerence and bravery can be substantial even in groups of large size.

Selective pressure is the extent to which a population of individuals (or ancestor for instance) may acquire either a beneficial genetic or cultural trait that gave them advantage and therefore made that group more likely to survive or lose a trait that drives that group to extinction.

According to the researchers, this pressure is driven by the benefits of conquest that also accrue on the relatives of the belligerent and/or brave males within their group, that shows how spoils of war are shared by those who're related.

To study how blood ties shape warfare, the research team came up with an idealised mathematical model consisting of an infinite number of groups, each with a finite number of adult males and of adult females.

The researchers have pointed out that "hunter-gatherer societies are well-known to have often raided neighbouring groups from whom they appropriated territory, and women".

They assumed random movements, and warfare, between the groups, and worked out how each group would have children as a result of the influence of genes linked with belligerence and bravery.