Footnote

b Sarah was the half sister of Abraham. Terah was father to both of them, but they had different mothers. (Genesis 20:12) While such a marriage is improper today, it is important to keep in mind how different things were back then. Humans were closer to the perfection that Adam and Eve had enjoyed but lost. For such robust people, marriage between close relatives evidently did not present genetic dangers to offspring. Some 400 years later, though, life spans were similar to ours. At that time, the Mosaic Law outlawed all sexual unions between close relatives.​—Leviticus 18:6.