It's most likely that both of your options are true. Which leads to the inevitable question. Did we reverses engineer craft from civilizations that have been visiting earth for centuries (simply look at religious art of the middle ages, it's filled of craft in the sky)? More then likely the advancement of technology terrestrially has been parallel our ability to understand advanced technology from other civilization from the far reaches of our galaxy or universe. Tell me, how did any of our megalithic structures needing advanced mathematics come to be constructed? Don't tell me they were made by people who did not have the wheel, pulleys and only stone or even bronze aged tools. Great topic that needs more de-stigmatized social debate and true transparency from our leaders.