As soon as there are multiple entities (countries, tribes, etc) that want the same thing (usually resources), there will be some level of dishonesty in order to

As soon as there are multiple entities (countries, tribes, etc) that want the same thing (usually resources), there will be some level of dishonesty in order to gain an advantage (because human nature). The definition of corruption is willingness to act dishonestly in return for money or personal gain. Given a tribe is big enough, it'll have multiple sub-tribes in it. Now go back to paragraph one. That's why politics is corrupt, as soon as a tribe is above a tiny size, people act dishonestly to further their sub-tribe's interests.