My uncle posed this question to me, and I had not ever wondered about it before, but now that I think about it,it is a mystery.
Genesis 4:15-16 (New International Version)
15 But the LORD said to him, "Not so; if anyone kills Cain, he will suffer vengeance seven times over." Then the LORD put a mark on Cain so that no one who found him would kill him. 16 So Cain went out from the LORD's presence and lived in the land of Nod, east of Eden.
If the only people on earth were living in the Garden of Eden, were there people also living in the land of Nod, and if so, where did they come from?