The human personality shows a striking diversity around the world. But when, how and why did this diversity evolve? In my PhD thesis I intend to present a general hypothesis and simulated models that could help us answer the above questions. My main contribution is a theoretical one: the agricultural trigger hypothesis states that the last and perhaps biggest explosion of personality diversification happened along the Neolithic Transition. The line of changes that accompanied the appearance of agricultural societies, like sedentary life, bigger settlements, hierarchy and society-wide social division of labour, all acted as to enhance behavioural diversification. While in small and mobile pre-agricultural bands specialization and extraordinary personality types were most likely to be counterselected, in the present civilization these could mean a significant selective advantage. The transition between the two selective environments probably happened hand in hand with the appearance of fully agrarian societies and the diversification of personality continues still then. The whole process of personality diversification is far too complex to study as a whole, but certain subprocess of it, like the appearance of heritable specialization by social division of labour or a change in the selective environment, I modelled by computer simulations. Thus far I have the above results to include into my PhD thesis, and I plan to complete the work with a multilevel selection model about how the within and between group selective process contributed to the transition.