“Since many of the Sun-like stars are billions of years older than the Sun, the Earth should have already been visited by extraterrestrial civilizations ...”
Some believe that this possibility is the explanation for how some extremely precise structures exist that carbon date older than man. I am inclined to think that Homo Sapiens could very likely be HS v3.0 or so, some version of an experiment in how to develop intelligent life.
FWIW ...
When the first stars were created, they were made of 100% hydrogen, as was the entire Universe. It was in those early that stars commenced to make helium over the next billion years or so.
Only by the process of new star creation, and then end of life in a huge explosion of Novas and Super Novas, could the other elements be created.
How long did this take, to be able to create a solar system such as ours, made of, still, primarily of hydrogen, but with enough iron, oxygen, boron, carbon, magnesium, sulfur, chlorine, sodium, silicon and all the other elements to get rocky worlds like Mercury, Venus and the Earth, let alone the chemistry to grow and sustain life?
This could have taken many billions of years. We don’t know, but it certainly didn’t take place right away; the elements just weren’t there.
I propose that given the Big Bang happened 13 billion years ago, and our planet and solar system was formed 4 billion years ago, that it just might have taken 6 or 7 billion years to make enough of the heavier elements that life could derive from.
I think we are close to the first, or right now, a lot of civilizations are just starting. Now, any civilization 100,000 years older than ours would be an AWESOME civilization, if they’re even into technology, advancement and space faring (and there may be those who just want to live and contemplate their alien belly button equivalents), but how would we even know about them, or they us, given not only the time it took to make anything resembling a place life could form, let alone those millions or billions of light years of distance?