Here is a scary conjecture I present to you: We often look up to the sky, wondering about aliens. Are there other life forms out there? Do they know about us? Why haven't they came? If there are other life forms out there, then there should be no reason why they haven't came to our planet given the huge time span of our universe? As we should know, we aren't very special beings. Our star was born during peak star formation in our galaxy. It makes sense that the elements on Earth would be where they are, as gravity will force denser elements towards the center. It is inevitable that life would be carbon based, because of the properties of carbon. It is inevitable that we would need a liquid which stays liquid at a wide temperature range, water. It is inevitable that the building blocks of life would be amino acids, because they're everywhere we look. Life as it is, is simply inevitable. However, as you may also know, life has gone through some serious shit to get where it is today. Life can be traced back to the late-heavy bombardment period, and has been through multiple mass extinctions. Therefor, we can say that for evolution to amount to the complexity that it has thus far, the "intelligent life form" as we call it, it has to take roughly the age of Earth. In each of the aforementioned mass extinctions, the dominant organism is the first to go. The dinosaurs had to die for humans to rise. The aerobic bacteria killed off the anaerobic bacteria when the amount of oxygen in the atmosphere increased. If humanity were to die out, it is likely too late in the life cycle of this system for life to evolve to this complexity again. The Milky Way is no longer in its era of peak star formation. The question that keeps me up at night: What if the reason we haven't seen anything, is because those alien civilizations didn't make it off their planet soon enough?