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Monday, April 04, 2005

Mrs. Cain? Inbreeding in the Old Testament

My friend, April, asked about how a good God would allow early humans to marry close relatives, which is, later in Scripture, prohibited. Ish responded to her, saying, basically, that the problem with incest is that close relatives would be more likely to have the same bad recessive genes, but that Adam and Eve were presumably created with a perfect genotype, so this wouldn't have been as big a problem for their immediate descendants. I agree, but wish to expand upon this idea.

It's probably best to distinguish between incest and inbreeding, but there is not a clear distinction. Incest, sexual relations between close relatives, has been frowned on by most societies. The Old Testament bans some specific sexual relationships, quite a few, in fact, in Leviticus 18. (At least in the NIV, it doesn't say it's banning marriage, but sex. I suppose that banning sex between, say, brother and sister would also prohibit marriage between them, but I'm not certain of that.) Inbreeding is a more general term. Inbreeding, to a geneticist, occurs when offspring are born to parents who are more closely related to each other than the general population is. There is a statistic, known as the inbreeding coefficient, which can be calculated.

Presumably, Adam and Eve were created with a perfect genotype. The Fall probably would have allowed mutations, gradually putting bad genes into the gene pool. This is consistent with the ages given in Genesis--they gradually got shorter and shorter, as would be expected as more deleterious genes came into the gene pool.

If they had perfect genes (no recessive bad ones) then inbreeding wouldn't matter, genetically, at least.

There are reasons other than genetics that make incest (or close inbreeding) bad, but the first humans would have had no choice, if they were the only possible mates for each other. Cain, and Seth, and maybe Abel, would have had to marry their sisters.

Were the first humans the only possible mates for each other? Probably.

However, there is the legend of Lilith (which is extra-biblical) who was another wife to Adam. George MacDonald wrote fantasy in the 19th century. C. S. Lewis was influenced by his writing. In MacDonald's Lilith, Adam, Eve, and Lilith are all characters. If there was another wife, then it would be possible to marry half-siblings, rather than siblings.

Genesis says:
Gen 6:1 And it came to pass, when men began to multiply on the face of the ground, and daughters were born unto them, Gen 6:2 that the sons of God saw the daughters of men that they were fair; and they took them wives of all that they chose. Gen 6:4 The Nephilim were in the earth in those days, and also after that, when the sons of God came unto the daughters of men, and they bare children to them: the same were the mighty men that were of old, the men of renown. (ASV, which is public domain)

Some interpret this as meaning that angels and humans married, although most seem to doubt this, for a number of reasons. This verse, of course, is not until Genesis 6, by which time Cain, Seth, and other generations of humans would have already had to marry somebody. There are other interpretations, such as that Seth's descendants married Cain's, and no one seems to know for sure what it means.

Madeleine L'Engle, Christian fantasy writer, wrote Many Waters (I don't usually link to Amazon, but they allow searching inside the book.) which supposes that humans of Noah's time could mate with demons, apparently basing this idea on the text above.

In Tolkien's Middle-Earth, there were three marriages (maybe four--see the article on Half-elven in the Encyclopedia of Arda) between elves and humans, and Eärendil, Elrond, Arwen and Aragorn were among the descendants of such unions. Tolkien didn't think of elves as like angels, but they were clearly different than humans. Maiar were more like angels. Melian (See entry under her name in the Encyclopedia of Arda) was of the Maiar, and married Thingol, an elf. They had a daughter, Lúthien. In C. S. Lewis' Narnia books, King Caspian married a star's daughter, and they had a son, Rilian.

Some believers think that God took pre-humans already in existence (Neanderthals?) and gave them souls. If that is what Genesis means, then presumably there could have been matings between humans and pre-humans.

Some ancient societies apparently did allow, and encourage, incest, at least in their royal families.

Abraham and Sarah were half-sibs, and Isaac and Jacob both married relatives. See the chart below (It should be possible to see larger versions of these charts by using either of them as a link, which will transfer you to Flickr. In Flickr, which doesn't require any password for such uses, you can click on the Down Arrow, to the right of the page, to download a graphic. That lets you see, or download, larger versions of the graphic.

Terah's family
There was marriage between relatives in David's family, also:

As to incest being evil, it is now. That doesn't mean that it was always evil. God had a different set of expectations for the Jews than He does for Christians. He at least allowed polygamy in some of His closest followers (although it often led to serious family trouble) in the Old Testament, but there doesn't seem to be even a mention of it in the New.

What about the question of inbreeding

A God who is capable of creation from nothing shouldn't have had any problems with giving Adam and Eve perfect genes, so that if Seth married a sister, it wouldn't have had bad genetic consequences. Even if Eve was created literally from Adam's flesh, He could have given them different sets of genes, so that apparent inbreeding wouldn't have mattered. I would guess that Eve at least had a second X chromosome, whereas Adam had only one, so that their genes were partly different.

This is all speculation, of course. The Bible doesn't name Cain's wife, Seth's wife, or Abel's wife (if he had one) let alone where they came from.

* * * *
This material was modified or added on April 6th, 2005:

The charts above are free for use, provided that any republication also allows free use by others. You can probably get a larger size through Flickr -- the two charts are links to the original charts, on my Flickr photostream. If I have made any errors in the charts, I'd appreciate knowing it. Leave a comment. Thanks.

October 17, 2007: I modified the charts, mostly adding more people, and making the chart of David's family more useful for general Bible study. I haven't checked to see if April's and Ish's web pages, that I referred to in the beginning of this post, are still available.

February 1, 2014: I modified the chart of David's family slightly, and changed the font size of the post. 

October 20, 2014: I modified the chart of Terah's family.

Thanks for reading and looking!


Ish said...

Good work, I agree.

April said...

Wow, Dr. LaBar! You've really done a wonderful job of answering my question. Thanks so much for the blog!

Rey said...

Excellent post. Excellent!

Anonymous said...


Martin LaBar said...

I'm not sure what you are saying, Anonymous, but thanks for commenting.

Anonymous said...

Hello everybody,
If the bible tells the truth, then the earth population of today doesn't derive from adam and eve, but from Noah, his 3 sons and their wives.
Did they have perfect genes too?
How would you explain to me the different races, Asians, Negroids, white and Mediterranean Caucasians, Arabs, people of the Pacific?
How also would you explain me that Noah peopled the earth in less than 5000 years?

Martin LaBar said...

Thanks, David Grahn-Amar.

1) The earth's population does derive from Adam and Eve, but with a bottleneck through Noah's family, apparently.

2) The Bible does tell the truth. We (including me) don't always interpret or understand that truth correctly, and, unfortunately, sometimes present our mistaken interpretation as if that is what God wants to say.

3) The Bible does not say that Noah and the flood were 5,000 years ago, or less than that. This is an interpretation. It may be correct, it may not. Perhaps it was much earlier. There are also serious Bible scholars who don't believe that the flood was a world-wide event.

4) I would be very surprised if Noah and his family had perfect genes. Presumably radiation and other mutagens had been acting for at least a thousand years by Noah's time.

5) The different races must have come about by descent, with modification, from the original stock. If Noah and his family were ancestors of everyone, then from them. To get different races, there must have been isolation in different areas of the earth, and selection for different things. Such selection is responsible, according to science, for darker skins in groups living near the equator, and for larger lung capacity in those living at high altitudes, and probably for the stockiness of Eskimos, among other traits. Could this selection have developed all the types of people in 5,000 years? I'm not sure.

6) According to a quick Excel calculation, 6 people (Noah's sons and wives) doubling themselves every 100 years could produce over 6 billion people in 3,000 years, so that's no problem. Doubling every 100 years seems quite possible.

Anonymous said...

Martin, It is funny how not only you never replied my latest post but too that you deleted it.
But it's alright, the withdrawal of informations is typical with pseudo scientists of your kind.
It didn't go your way, you didn't like it.
See science is about challenging the existent, finding how.
If you cannot take challenge, I only have one word for you, you are not a scientist.
Stop fooling yourself and the people around you.
If you are that into the bible, then don't lie.
To everybody else: Martin labar coudn't was unable to defeat my argument so he simply deleted it.\
He's a lier, a coward and a fake.

Signed David Amar

Martin LaBar said...

I'm not deleting this one, even if I am a "lier" [sic].

I honestly (!) can't remember deleting your comment, and I can't remember what it was about. I checked my e-mail (where all comments go) and whatever it was, if it ever was posted in the first place -- sometimes, as you probably know, Blogger has a glitch and a comment doesn't get posted -- this was over a month ago. I don't normally delete comments unless I consider them to be spam -- advertising commercial or other web sites irrelevant to the post. There are various comments, here and there over nearly five years of blogging, that disagree with what I have posted on a number of subjects.

If you want to put whatever it was that you said in a comment again, I'll look at it again. I am sorry to have offended you.

By the way, my name is LaBar, not labar. I don't know yours, of course.

Anonymous said...

Well maybe if you read the comment you would know my name since it is signed ....

Martin LaBar said...

Anonymous/David Amar:

My apologies. I did read the comment, even quoted from parts of it, but apparently skipped the last line, zoning in on the Anonymous. I wasn't happy with being called a "lier, a coward and a fake," and I don't think you would have been, either.

I still can't recall the comment that you say I deleted, nor what it was about.

Anonymous said...

Very interesting, i like your theories. I think an update to Abrahams tree would be nice, since Esau married a relative through Ishmael.

Martin LaBar said...
This comment has been removed by the author.
Martin LaBar said...

Thank you, Anonymous.

They are just theories, though.

Thanks for the suggestion, but the chart is already pretty crowded. I wanted to emphasize the Israelites. I didn't include Lot's daughters and their offspring, either.

flynvfae said...

I've always wanted to know why the Old Testament seems obsessed with incest

Martin LaBar said...

Thanks, flynvfae.

I think it's "seems," not really obsessed. The Old Testament (to us) seems obsessed with family lines and connections, and a lot of those were within families, because that's the way they did things in those days.

Anonymous said...

The stories of the flood, and Adam and Eve, Pharoahs, Kings and overacheivers are all failed attempts of the ancient author to explain the phenomenon of overpopulation inbreeding in ancient Egypt. When human populations experience large population growth the person with the genetics to have the most children has a family tree which in future outnumbers everyone else and feeds back on itself. This means that the population becomes inbred to acquire the genes to have the most children. This means, that you are inbred, as is almost all mankind. While people still perceive that their fourth cousin is a low enough level of incest, in actual fact your fourth cousin is as closely related to you as your sister used to be in ancient times. Keep this is in mind before having children, because they may well turn up slanty eyed inbreds. There is also the wide eyed inbred (see India).

Anonymous said...

When Cain killed Abel it is a comment on the fact that Egyptians violently hated the slightest dissimilarity which is a feature of overpopulation inbreds.

I believe the creation occuring in seven days is a reference to the number of days in a row in which a woman may become pregnant. It alluded to overcopulation and overpopulation of civilized agricultural peoples. After all, the Bible was designed as the text to accompany the marriage ceremony within the relatively new idea of civilizations which kept turning out inbred populations.

Martin LaBar said...

Thank you, Anonymous. You have some interesting ideas. I'm afraid that I don't believe most of them. I'll deal with just one.

You wrote "your fourth cousin is as closely related to you as your sister used to be in ancient times . . ."

Really? I have a doctorate in genetics, and was taught, among many other things, that even if the parents were totally unrelated to each other, full siblings share 50% of each others' genes, on the average. (Sometimes more, sometimes less, but on average.) How a fourth cousin could possibly be that closely related, even in some special isolated communities, where there is a high degree of inbreeding, such as the Old Order Amish, I have no idea. Most people in North America don't marry known close relatives.

Thanks for your comments.

Anonymous said...

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Martin LaBar said...

Thanks, Anonymous.