There's also the matter of probability. Whatever the improbability of life arising on its own on earth and evolving to the present level of complexity, the probability of a two such forms of life arising on their own elsewhere and achieving a similar level of civilization is the first improbability squared. For three such civilizations, the probability is the first cubed and so on. The likelihood is that we're all there is.
Nope, the probability runs differently. Our planet revolves around a relatively new star. We've had three billion years to develop to our present state, with most of the real progress in just the last 4,000 years.
There are billions of suns, many with potentially habitable environments, that are ten billion years old. The odds are in favor of life developing on several of those, and having the time to far outstrip our current state of development.
Unless we are absolutely unique, odds are we have neighbors who are way ahead of us.
Congressman Billybob
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