Even Cavemen Knew That Incest Was Wrong
This one’s gonna be tricky.
I grew up attending a small country church where biblical inerrancy was staunchly reinforced on a weekly basis. Evolution was a lie and Science was a tool the Devil used to mislead people. The world was only a few thousand years old, and anyone who didn’t believe it was going straight to Hell. Okay, then. Let’s say Adam and Eve were the first two humans on the planet. Then they had kids. They had sons who grew up and took wives; then they were all fruitful and multiplied. Where did those sons get their wives? Either some mental calisthenics are required–God created other humans but the Bible neglected to mention it–or else brothers were marrying and mating with sisters. Yep. Hardline fundamentalism states that God approved of incest.
We know that incest leads to birth defects. And we know that, as far back as 34,000 years ago–sorry, young Earth fundamentalists–people knew that it was something to be avoided. (Even chimpanzees and other primates tend to avoid it, hinting that the “knowledge” is instinctual.) We don’t know if there was any moral imperative attached to this act of avoidance or if it was a matter of mere practicality. What we do know is that our primitive ancestors were being fruitful and multiplying, just as God had instructed them to do, but were smart enough to send their young bucks out in search of mates from outside their extended family groups.