@awnlee jawkingBy my understanding of current "standard model" of cosmology, all matter that exists today was created in an extremely short epoh of faster than light expansion shortly after Big Bang in a process known as "inflation." Many more matter and antimatter were created, but almost all of that annihilated, what we have left with is small imbalance in mater/antimatter symmetry thanks to some particles being their own anti-particles.
Trouble was, that matter was almost evenly dispersed. Negligible perturbations led to gravitational collapse over time leading to the universe we know.
Yes, the interstellar/intergalactic gas that is everywhere (very near, but not ideal vacuum) need to compressed to create stars, but that can happen in many different ways, and galaxy centers aren't the most benign environment for that today. Instead, most stars form in the shockwave where's the rotating galactic arms met the intergalactic medium.
Astrophysicists call everything heavier than helium "metals" or "heavy elements" because all that has to come from dead stars exploding and didn't exist in the initial universe originally (except, perhaps, trace amount of lithium). I go on this aside to point out, universe just about now reach conditions for life (as we know it) to exist. It is theorized we might be within the first 5% of civilizations possible. However, billion years older civilizations can have existed (if any still existed, in our galaxy, we would probably know) they're just even more improbable and thus rare.
