Some say we were created by God, some say we were interbred with/by aliens, some say we just evolved from apes, some say we evolved out of the oceans, so many theories!
But then you have to think, if we were created by aliens, who created the aliens? If we evolved from apes, then who created the apes? If we evolved out of the oceans, who created the ocean life?
Some also say God is/was an alien, so who knows ...
In the end it does not really matter, we are here regardless of how we got here.