I tried to ask priests about that, but received no viable answer, maybe I'll try more because it really interests me, how Christians perceive it.
I received however an interesting answer from a Jewish woman: she said, at least according to some rabbis (dear Jewish friends, correct me, but, as we say in Russian, "I sold it for the price I bought it"), that it's more of a symbolism that Adam was created. That means, he was the first man (and Eve, the first woman) to have spiritual experience and to communicate with God himself, so there were other humans, just not spiritually enlightened. Again, it's what I was told, but to be honest, this subject has always interested me from the theological perspective. I'm not a Christian, but learning religions is always interesting.