So we know the Andromeda Initiative was initialized by humans in 2175.
By then, humans had developed spaceflight 220 year before and know of the Mass Effect Physics since 2148..... so we are damn knew to this.
The Asari discovered the Citadel 2700 years prior, the Salarians shortly afterwards.
I don't see the Humans as an Uberspecies and our whole cycle is less developed than some others before us, like the Protheans and who knows else.
So if we are capable of successfully traveling to Andromeda, and considering the Reaper Mandate to preserve life is restricted to the Milky Way alone, it might be possible (and awesome imo) to find traces or even members of species from previous cycles who found refuge in Andromeda, as they would have considered this journey aswell.
Or some big bad evil Native Andromedaian Races whiped them all out and therefore we find nothing.