Paradox of the ego - our desire to improve vs Buddhism

There was a question on my mind lately, regarding ego. It is not paradox per se but I find it slightly paradoxical. Because people have such a strong ego, humanity has risen above the animal level. Our ego was main reason that we progressed, our desire to improve etc. If it wasn't for our ego, we would still be in caves, struggling and Buddhism would never exist. Isn't this paradoxical? Ego is the main reason that we came to the point where we are trying to forget our ego?