I'm a physicist by trade but my specialism is particle physics, not astrophysics. Ask someone else about first-/ second-generation stars, or find a wiki and I'm bored by now of being cited as the ultimate AB authority on literally everything with "physics" in the title. It only leads to silly arguments
An intriguing article popped up recently:
http://www.iflscience.com/space/earth-may-have-formed-earlier-92-other-habitable-planets
the basic claim being that there is a high probability that we're quite early in terms of civilisation development; the actual research is behind a paywall and I haven't got around to reading it yet, but it could have something of an impact on the likelihood of the alien astronaut theory. Or not, since the numbers in question remain arguably large enough to support it. Still, I thought it worth sharing one way or another.