Doesn't every major currency issuer need the explicit backing of a large and expensive army? The USD in many ways would be a joke if it wasn't for the fact we've got the biggest hammer.

(I'm not disagreeing with the above, just using this as an opportunity to write about something I've thinking about lately.) One of the reasons humans have 'taken over' is because our individual missions can all be different, though the main goal of our lives is survival. For example, some of us become computer scientists to acquire currency which we use to buy food, while others might become doctors to accomplish the same goal. When we are at our best our individual missions sync and we benefit each other. What is even more unique about humans is that we can adapt as many times as we are emotionally capable of during the course of one life time. So not only can we learn a skill, but we can change our skills. It is possible to think of several reasons why 1000s of years ago our primitive, desert-dwelling Christian ancestors banned homosexuality. Luckily the world is different now. As a species we can afford a non traditional family unit for homosexuals, heterosexuals, and everything in between. Christianity is slowly fading as the 'ethos' that syncs our society and therefore our individual missions. Or rather, it was religion+government that gave us a sense of unity, now it is just government.