Why we can’t have nice alien friends
If we propose that Earth's "intelligent" civilization is dependent on our place in the solar system e.g. Goldilocks location, what other factors (besides luck or external hands) has allowed the evolution of chemicals> bacteria> algae> Flora> Fauna?
Quite simply, we have Luna, mixing our tides.
and Luna was caused by the glancing blow of Theia with the proto Earth.
To see why this is so important, just do a little microbiology experiment:
Take two Erlenmeyer flasks, some simple nutrient media, throw in some bacteria and put one on a shaker table and let the other one stay static.
Both flasks show growth, but the static flask soon becomes covered with dead bacterial debris and goes anaerobic followed by culture death. The flask on the shaker continues to thrive way past the anaerobic conditions on the static flask.
While the bacteria in any closed environment will never "evolve" past being bacteria, in an open system similar to earth, with dynamic Luna mixing, flowing water, solar, volcanism and electric (lightning) energy sources, life can grow, modify and change.
While we can't postulate how different populations will evolve given different input, we have to draw conclusions from the only currently known planet with a relatively advanced civilization. We must calculate the odds of having a planet in the Goldilocks solar zone, with a moon large enough to diurnally move the tides.
If a Theia-type glancing collision is required to create this moon, the odds of having an advanced civilization are significantly reduced from any calculations based just on Goldilocks zones and water even with the 60+ billion candidate planets currently proposed in the Milky Way.
Look around our solar system: Mars may have water, may have had/has valid temperature ranges, but just look at those dinky moons.
1) Planet earth has an intelligent population.
2) Erlenmeyer Flasks experiment has the correct temperatures, lighting, airflow and nutrients.
3) You can Google/Bing Erlenmeyer flask if you don’t know what that is (see Assumption #1, above).
4) likewise for shaker table, anaerobic and other microbiology terms.
5) you have access to/can grow pure or known cultures of bacteria.
If intelligent alien life is discovered now or in the near future, all of these proposals may be thrown out the window.