When it talks about in Genesis of God creating Adam and Eve there's always been a mystery of where Cain and Able got their wives from but I think I know now. It definitely says that Adam and Eve were the first humans on earth, but what if God created humans after them and they had children as well? Even though it isn't included in the Bible, not all of Jesus' life either so it fits.
Sorry, but the English Bible translations do not go into the detail of Genesis 1:26-27 that the Hebrew does.
In Genesis 1:26-27, 2 separate groups are being created by God...
1.
eth'ha'aadam = this man Adam, a singular man Adam
2.
aadam (no article, no particle) = general mankind
Both of those Hebrew words appear there. The idea is the same in all languages when speaking of a singular object vs. the plural. If I say, 'this man built a house', that is about a singular man. But if I say, 'man builds houses', that is about many men, plural.
That is how the Hebrew about the creation of man in those Genesis 1:26-27 verses is.
What does that mean ultimately??
It means that on God's 6th Day, He created BOTH a single man Adam to till His Garden, and also the races of mankind and placed them outside His Garden. When Cain was booted, he went to the "land of Nod" where there already were people there.