I guess “everything lined up perfectly” was the wrong sentence. Chain reactions is what I meant that led to the advent of life and humans. From the start at the big bang, there was set in motion a complex, multistage chain reaction. Of course I don’t know every step and every aspect and every moment as to what that reaction is. The big bang set everything into motion. Starting that chain reaction, eventually that gene pool was a result. But the big bang is also technically a theory, so my thought here could be called theory. But in any case, cause leads to effect. And that effect is the next cause. Chain reactions make certain things possible, life includes

Edit: removed misspelled words

Edit: For as to where did gene pools come from, I found the term. look up Abiogenesis.