Amen, but Adam's daughters married and produced children with the sons of God (prehistoric man) on Adam's Earth
"and also after that" on the present Earth. Genesis 6:4 This changed the sons of God into Humans because they had inherited Adam's superior intelligence, which is like God's. Genesis 3:22
Gen 6:4 There were giants in the earth in those days; and also after that, when the sons of God came in unto the daughters of men, (Hebrew-Adam) and they bare children to them, the same became mighty men which were of old, men of renown.
The giants are giants intellectually since they became Humans (descendants of Adam)
AFTER their Human parent married one of the sons of God. Cain did it on Adam's Earth and Noah's grandsons, having
NO other Humans to marry, did the
SAME thing on the present Earth. Genesis 10:8 Today's Humans are the "
giants" and have the superior intelligence of Adam. It's the
ONLY way to become Human since no amount of mindless time nor zillions of mutations can place God's intelligence into the brains of Apes. That's God's Truth Scripturally, scientifically, historically, genetically and mathematically.