Luiglin
Getting worse one day at a time
I'd point out that many animals - humans included - have the instinct to seek out others of their kind, to better serve that self-preservation.
I would further argue that self-preservation has little to do with being corrupt or not, and that the "me first" attitude is, in actuality, a deterrent to the self-preservation sought. In tribal animals, the success of the whole enhances the survival of the individuals within. Forgetting this truth - which I fear our society is in danger of doing - would literally result in the destruction of the group, to the detriment of the individuals.
I agree, the pack instinct is strong. I was talking more about the extreme sort of individuals, those that will happily tread on others to get what they want. The sort that would willingly do whatever they can to gain or retain power. There's more than a few where I work.
I was going more with the idea from the OP about power corrupts. These sort would happily accept that corruption once they gained the power in order to retain their position.