If this was based on fossilized human bones (of say 6,000 years plus old) as opposed to human beings in the here and now, it could be understandable based on a reading of Genesis 6 and an understanding of who the ‘daughters of men’ and the ‘sons of God’ are....and why God sent the great flood of Noah.
Verse 2 says this.... “That the sons of God saw the daughters of men that they were fair; and they took them wives of all which they chose.”
God did send the great flood for a reason....
Supposedly that refers to fallen angels, but not necessarily the ones that followed Satan. They have the propensity to wander off the plantation from time to time...............