Incest in the Bible: Does God Change His Mind?

If Adam and Eve were really the first humans, doesn’t that mean that their children had to have had incest to have children? If the answer is “yes” we might run into a few big problems: namely, doesn’t this defy God’s law in Leviticus 18? Isn’t God’s law and will eternal? If the answer is “no,” however, we run into even bigger problems. 

First, let’s explore the possibility that Adam and Eve’s children didn’t procreate with their siblings. For this to be true, other humans must have existed outside of Adam and Eve. Right off the bat, we run into a swarm of issues. Most obviously, there’s absolutely no evidence in Scripture for this. In fact, there’s a lot of scriptural evidence that seems to go against it. One way someone could try to work other people into the Genesis 2-3 narrative is to allegorize Adam and Eve. “Adam” in Hebrew does mean “humanity” or “all of humankind” and Adam is a representative of all people. However, “Adam” being a representative for all people doesn’t necessarily mean that he wasn’t a single person himself. The Genesis 2-3 narrative depicts Adam as an individual. If he weren’t a historical person, why not change the narrative to show God creating multiple “Adams” and their numerous “Eves”? The allegory would be no less effective and even more precise if that’s how history actually unfolded. 

Furthermore, Scripture doesn’t treat him as merely allegorical. Both Adam and Eve are historical individuals according to the New Testament. 1 Corinthians 15:45 states that the first man Adam was made a living soul. All of the language here is singular, not plural. It’s not saying that “humans in general” were made living souls. He was one living soul. Most importantly, Romans 5:12-21 contrasts the disobedience of one man Adam and the obedience of one man Jesus. See Romans 5:19 “For as through the one man’s disobedience the many were made sinners, even so through the obedience of the One the many will be made righteous.” This theological comparisons relies on Adam being a single individual.¹ In two separate places, Paul asserts the historicity of Adam as an individual. In 1 Timothy 2, Paul then speaks of the relationship between Adam and Eve, also treating Eve as a historical individual. Though they do represent all of us, they were still real people. 

There are essentially only two possible benefits of this “other people” interpretation: one biological, and the other theological. Biologically, it avoids inbreeding and the various ramifications that come from it. Theologically, it keeps God’s attitude toward incest constant through all of the Bible. If Adam and Eve really were the first and only two people at the outset of creation and their children had to procreate with their siblings, doesn’t that mean that God allowed incest, at least for a time? That leads us to ask a ton of other questions. When did God “change His mind,” per se? Why did God outlaw what He initially intended? What about God’s law being eternal and unchanging? 

The more I think about all this, the more I’m convinced in the orthodox view. The “other people” allegory, as problematic as it is already, has no way of addressing Noah and the flood except to use the same explanation: “It’s only an allegory; other people must have survived the flood as well.” All this starts to become a slippery slope. At what point do we stop calling things mere allegories? Who determines what was historical and what wasn’t? 

It seems God allowed this sort of incest for a time up until Moses at the latest. Some scholars try to argue that at first, procreation between close kin didn’t have the same negative effects it does today.² Even if this is true—and I’m given absolutely no evidence that it is, either in Scripture or in scientific research³—biological evidence shouldn’t be applied to a moral argument. They’re categorically different. God’s reasoning from barring incestuous relationships seems to be the same as his reason for enacting dietary prohibitions. It comes down to a matter of “defilement” or “cleanliness.”⁴ I don’t think there’s any correlation between genetic health or diversity in reproduction and God’s reasoning in Leviticus 18:24-30. That’s not to say that God is not at all concerned with matters of biology, reproductive health, and genetic diversity. He very well may be, but that’s not the reason He gives to Moses for why Israel must abstain from incestuous relationships of various sorts. I don’t know if there’s a term or concept that addresses “accidental benefits” of Mosaic law—for instance, the claim that the kosher diet has clear scientific health benefits—but that’d be a topic I’d love to look into more.

What’s even more interesting is that dietary laws are abandoned in the New Testament.⁵ The same liberty, however, is not extended to sexual immorality—πορνεία (porneia) in the New Testament—including incest. Acts 15 clearly bars all forms of sexual sin, and the epistles elaborate further on specific examples of porneia including incest in 1 Corinthians 5. Christ Himself teaches regarding sexual lust “everyone who looks at a woman with lust for her has already committed adultery with her in his heart” (Matthew 5:28). This, of course, speaks to the sinful desires of the human heart which rebel against the will of God: proper sexual desire is between one husband and one wife. To my knowledge, we never receive any comment on why marriage between siblings and cousins is never re-permitted.

I have to point out that there is a significant difference between Leviticus 11 and Leviticus 18. God’s motivation behind dietary laws is to make Israel holy and distinct; they need to be unique and separate from the other nations. It’s a positive reasoning. Israel will be holy and distinct by its obedience. In contrast, God gives Israel a warning to refrain from incest and other sexual perversions “so that the land will not spew you out, should you defile it, as it has spewed out the nation which has been before you” (18:28). This is a negative reasoning. Israel will not be spewed from the land as long as it doesn’t defile itself. In other words, there’s no explicit punishment for gentile nations eating unclean animals. However, there is an explicit punishment for committing incest. 

What we’re not given is any explanation of why incest is all of a sudden a punishable offense when it used to be permitted. “It was a necessity to fulfill the creation mandate” seems entirely unsatisfactory to me. One could try to bring in Matthew 19 here and say, “Well, divorce was never supposed to be permitted, but God made an allowance of it because of the hardness of our hearts. God saw it a fit mercy to allow divorce in specific, tragic circumstances because of sin.” Yes, that’s true. God does make at least one allowance to go against His created intent because of sin. However, that doesn’t speak to incest. If Adam and Eve hadn’t sinned, they and their offspring still would have had to fulfill the creation mandate; incest would have been inevitable in this sinless world. So the question seems to be, what made incest become a defilement? Would incest still have been eventually forbidden in a world without the fall? I have no clue. What would I even research to answer this? 

What we can deduce is that at some time between Genesis 4 and Exodus 19, incest became a defilement. At some point it transitioned from being the natural, necessary way to procreate to a detestable abomination that God used as a reason to spew people out from the land in which they dwelt. Genesis 19 shows that incest between daughter and father was detestable in the time of Abraham. Yet, Abraham and Sarah were half-siblings according to Genesis 20. In Genesis 24, Abraham demands that Isaac’s wife come from his father’s household. Rebekah was Isaac’s first cousin’s daughter. God Himself ordained their marriage, so this specific instance is at least allowed some 400-500 years before Sinai. 

What’s likely at play is the difference between natural law and positive law. Natural law points to God’s immutable, underlying created order—the reasoning behind specific laws. Positive laws are the particular ways God instructs His people to live out His natural law. R.C. Sproul gives this example:

“The most common example is the Old Testament requirement that one build a fence around one’s roof. Do we still have the requirement? Is the American church under a cloud of judgment for not obeying this law? By no means This is positive law. The natural law is broader- do not put your guests or visitors in danger. In Old Testament Israel the roofs of homes were places for social gatherings. In America that is generally not the case. The consistent law, the principle underlying the specific, the natural law may have as its application here, put a fence around your swimming pool so no one accidentally falls in a drowns. We still are required to pursue the safety of those on our property.”⁶

With this in mind, we can answer the question “Does God change His mind?” with a firm “No.” Whatever underlying natural law that incest eventually came to violate was always the natural order of the world. I just can’t find any explanation of what that change was or when it happened. Sproul concludes his article with by saying that “Jesus is the same yesterday, today and tomorrow. His natural law reflects not only the nature of things, but His own unchanging nature. Circumstances may change. Our Lord does not. Neither then does our obligation to obey whatsoever He commands.”

I don’t know what can be said past that. In no way am I advocating for incest. As far as I’m concerned, it’s disgusting and unethical. There’s no debate that it is now considered sin and ought to be outlawed. I had hoped at the start of this study I would find a strong Scriptural answer that incest was never allowed. I’ve come to the opposite conclusion, and I won’t disregard the text. If you have any further questions or insights, let me know. 

……

¹ Romans 5 seems to make the further demand that all humans must be descended from Adam. Sin is not just something each person is guilty of themselves, it’s also an inheritance from our first parent. If this is the case, all people can trace their ancestry back to Adam as one person.  

² Don Stewart, Pentecostal preacher and author, claims that “in the beginning, there would not be the usual genetic defects arising from intermarriage among family members.” See “Degenerative Effects” https://www.blueletterbible.org/faq/don_stewart/don_stewart_717.cfm 

³ The primary scientific “evidence” used to argue for this position is a concept called genetic entropy. As scientific as it sounds, it’s not real. No peer-reviewed scientific journal has any published work on this theory. All instances of “genetic entropy” in any journal I’ve searched through refer to ideas that are entirely unrelated to the concept discussed here.

The main proponent of this theory seems to be John C. Sanford, author of the book titled “Genetic Entropy” published in 2005. This book has received ample criticism from geneticists. This review calmly and fairly assesses Sanford’s theory: https://www.amazon.com/…/RPW…/ref=cm_cr_arp_d_rvw_ttl… From what I can gather, “genetic entropy” is a theory that is at best well-intentioned but misinformed. At worst it is consciously dishonest and intentionally deceptive.

⁴ I make this claim from the usage of the word תִּֽטַּמְּא֖וּ (ṯiṭ·ṭam·mə·’ū) in Leviticus 11:43 and 18:24, 30

⁵ For the most part. Matthew 15:11, Acts 10, Romans 14, 1 Corinthians 8 all speak to Christian liberty with regard to old dietary laws. Acts 15 explicitly prohibits “blood and things strangled” which could be a dietary restriction of sorts. I haven’t looked too deeply into that yet, though I’ve always associated that with the command to not eat a creature that is still living given in Genesis 9:4. If that’s the case, it would seem to be more a matter of mercy and sanctity of life than dietary restriction. 

⁶ https://www.ligonier.org/blog/does-gods-law-change/

Scripture consulted:

Genesis 1-3, 4-5, 10-12, 19, 24

Exodus 20

Leviticus 11, 18

Matthew 5, 19

Acts 15

Romans 5

1 Corinthians 5, 15

1 Timothy 2