Alien Question for Atheists

[I_am_not_mafia]

But if we did find them then coevolution would be my hunch.

Just as an aside because it's twice now that you used it, but you actually mean convergent evolution. Co-evolution would be like predator and prey in an arms race where the evolution of one species changes the selection pressure on another species. Convergent evolution is when a similar solution is arrived at independently.

Easy to get them confused.