Science Ch.20 - Where Did Cain’s Wife Come From?

If Cain married someone living outside Eden, this would explain some strange details in Genesis. It would also explain how our gene pool contains so much variation.

I’m one of those annoying people who rarely get sick. It isn’t that I live a charmed life and avoid infections – I had all the normal childhood illnesses of measles, chicken pox, and mumps, but none of them caused me much suffering. I even caught tuberculosis (which can kill you) and mononucleosis (which can lay you out for months), but I didn’t have any treatment because I didn’t feel ill – I only knew I’d had them when they showed up in medical tests later. I recently found the likely cause of my good health when I had my genes mapped: I’ve inherited lots of Neanderthal DNA, which includes a heightened immune system.1

       This chapter will not conclude that Cain married a Neanderthal – though I love the idea that his punishment included marrying someone stronger who could stand up to him. However, our genetic inheritance is much richer and more complex than we’d expect if we had all descended from one incestuous family. As we’ll see, it is nonetheless possible that we all descended from Adam and Eve and still gained a rich gene pool.

       Cain could, of course, have married his sister – though the Bible doesn’t say this happened. It is difficult to imagine her wanting to marry a brother (especially the nasty brother who murdered the nice one). Presumably this incest wouldn’t be dangerous like it is today because God could have made sure there weren’t any dangerous recessive genes in Adam’s chromosomes. However, our human race would be very weak if the entire gene pool had been limited to just Adam’s chromosomes. Restricted gene pools often cause problems in overrefined agricultural animals or crop lines because this makes them vulnerable to pests and changes in the environment. This is solved by interbreeding with wild species to reinvigorate the gene pool by introducing more variety.

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Diverse gene pool

Fortunately, the human gene pool does have a lot of healthy variety. This includes far more than just differences in skin color and facial features; the most important differences are invisible, such as our biochemistry and immune system. A lot of this variety has no actual benefits at present, but variety future-proofs the species. Without it, we might get wiped out by a new type of infection that attacks a process that is identical in all of us. Our gene pool is very robust because the genes in our human population have a wide range of varieties (technically known as alleles).

       For example, we have three major blood types, A, B, and O, which all work well. These are produced by three significantly different versions of a single gene called ABO. Mixing blood of type A with type B will cause agglutination, which will kill someone who gets the wrong transfusion, but mixing with O is unproblematic. We all have two copies of every gene, so someone with A+A or A+O is blood type A; B+B or B+O is type B; and A+B is type AB. The rare person with O+O is particularly useful because they can be a donor for anyone.

       Actually, the situation is much more complex: there aren’t only three versions of this gene – there are about seventy.2 These seventy versions of the ABO gene divide into these three major groups, so normally we can ignore this complexity. But how did we get seventy different versions of the same gene if our ancestors are only Adam and Eve? They could only pass on four different versions of the ABO gene at the most. And if Eve was a feminized clone of Adam (as the text seems to imply), then there were only two versions of that gene available.

       It is possible, of course, that in the meantime mutations would produce more versions of the gene, but that would require a much faster rate of mutation than we see at present – in fact, it would be dangerously fast. Other genes have vastly more varieties – such as MHC (Major Histocompatibility Complex), which has eight hundred different forms.3 The mutation rate would need to be extremely high to produce all these differences in just a few thousand years.

       Mutations occur very rarely, unless there are carcinogens present. This is good, because most mutations are dangerous – as seen by the effects of carcinogens. Reproductive cells are protected from mutations by DNA repair mechanisms, which make sure that accidental mutations are rarely passed on to our children. A few do get through – on average sixty-four mutations – though this is tiny compared to the three billion base pairs that are copied perfectly.4 However, some of these are so harmful that they result in miscarriage – about 10 percent of pregnancies end this way. So even a small increase in mutation rate would result in a lot more miscarriages.

       The low mutation rate means that a new variety of a gene takes a long time to develop. The multitude of ABO varieties would take millions of years to arise – longer than humans have been around – so it’s not surprising to find that most are already present in other primates, from whom we presumably inherited them.5 These different varieties don’t confer any advantage, so there would be zero chance of them having occurred in humans by parallel evolution. This ABO gene is just one of the twenty thousand genes in our chromosomes, most of which also have several different versions that could not have been inherited from only two individuals.

       Very occasionally, a mutation gets inherited that makes a really useful difference. The FOXP2 gene has two tiny differences that produced the most significant development between us and chimps: language. Chimps have a slightly better version than the one in mice, whose FOXP2 gene only enables them to make ultrasonic squeaks – a single change enables chimps to make more complex noises. These kinds of useful changes happen only once in thousands or millions of years because inherited mutations are rare and useful ones are extremely rare. They are rare because the mutation rate is low, and this has to be low because most mutations are dangerous.

       Of course, God could at any time force an advantageous change to occur, so that useful evolution speeds up. However, the timescale over which changes have been observed to happen suggests that our genetic inheritance has been allowed to progress naturally. God could have interfered, but it appears that he was happy to let his creation work in the way he had designed it.

Neanderthal DNA

If all human beings did descend from Adam, we have to account for the diversity that now exists in our genome. This includes not only the large number of variants among human genes, but also the genes from prehumans – including Neanderthals and Denisovans – which many of us have. The most likely source of all these different genes is something the Bible doesn’t mention (but also doesn’t rule out): that there were human animals living at the same time as Adam.

       As I mention in chapter 19, when using the term “human animal,” I mean humans that were like Adam before God put a spirit into him. The Bible implies that the presence of a spirit that can communicate with God is what makes humans different from animals.6 If God made Adam from the dust, like he makes us from dust,7 then God picked him from a group of animals that looked exactly like him. They remained animals, while God made Adam into a “human being” – with a spirit that was passed to all his descendants. God put Adam into Eden, while the other human animals continued to live outside the protective wall around this special garden. This means they couldn’t eat from the tree of life that would have enabled Adam to live forever.

       When Adam’s family were thrown out of Eden, they would have been able to mix with these human animals and breed with them – though they probably wouldn’t want to. We don’t know whether their children would inherit a spirit like God gave to Adam, but there is a good reason to think that they would: a spirit was not withheld from Cain. Even after Cain had murdered his brother, we know he had a spirit because he was able to hear God ask him, “Where is your brother Abel?” (Gen 4:9). Adam’s two sons, Abel and Cain, were very different. Abel is called “righteous” (Matt 23:35; Heb 11:4), but Cain clearly wasn’t. And yet both of them inherited a human spirit. This suggests that God’s gift of a spirit to Adam’s family was irrevocable, and that every child inherited one and retained it whether they acted morally or not. In that case, if Cain married a wife who was a human animal (i.e., a human without a spirit), why would God stop Cain’s descendants inheriting the human spirit?

       This is pure speculation because the Bible doesn’t tell us whom Cain married. We can’t be sure that he married someone outside Eden, because the Bible doesn’t mention the existence of humans who hadn’t received a spirit like Adam did. But neither does the Bible rule this out – it is simply silent about it. We are equally unsure that Cain married a sister, because the Bible is silent about that too. All the text tells us is that he got married and went to a land called “Nod,” where he founded a city (Gen 4:16-17).

       Actually, if Cain did marry someone outside Eden, this helps to explain quite a few interesting details in the text – for example, his fear that “whoever finds me will kill me” (Gen 4:14). Of course, he could simply be inventing some danger, so that his family wouldn’t make him leave. However, God took him seriously and said that “anyone who kills Cain will suffer vengeance seven times over,” and he “put a mark on Cain so that no one who found him would kill him” (v. 15). Who was Cain afraid of, if Adam’s family were the only humans on earth? At the time, Adam had no son other than Cain. So even if he was afraid that a future son of Adam would come after him for revenge, Cain would have a twenty-year head start to get away out of danger. However, his fear that he would meet someone “out there” makes perfect sense if human animals lived outside Eden.

       Although I use the rather derogatory term “human animals,” there is no reason to think that they were less intelligent than the human beings – Adam and his descendants. They had the genetic capability to speak and think as intelligently as human beings (i.e., those with a spirit). They presumably showed the full range of human emotions, just like other intelligent animals. What they lacked was the ability or desire to communicate with God. If a colony of them had survived in a hidden spot on the planet, we would have found people who had no religion. That doesn’t mean they would be like atheists, because they wouldn’t feel any need to deny God’s existence either – the idea of God would never arise. We would expect them to display no appreciation of religion or any interest in pursuing the topic when it was introduced, and they probably wouldn’t think of doubting it any more than they doubt that the North Pole exists. We have never found a tribe like that, but it isn’t impossible.

Life outside Eden

If other human animals did exist at the time of Adam, this helps to explain other curious matters we discover in the text of Genesis. One of these is obvious but not trivial: Where did Cain find a wife? The text simply says: “Cain went out … and lived in the land of Nod, east of Eden. Cain made love to his wife” (Gen 4:16-17). This sounds strange – the wife seems to appear out of nowhere. He either took a sister with him, or there was already a colony of human animals east of Eden and Cain married one of them.

       The description of Cain’s life also makes more sense if there were already others outside Eden, because it explains who lived in the “city” (or “town”) that he built. Genesis says his wife “became pregnant and gave birth to Enoch. Cain was then building a city, and he named it after his son Enoch” (Gen 4:17). We could, of course, interpret the text as, “She gave birth to Enoch. Cain was then [much later] building a city [to house all his grandchildren and great-grandchildren].” Or instead, it could describe Cain wanting to organize the people among whom he lived, and starting by founding a town where they could live closer together.

       Human beings (those descended from Adam) may have been much better at cooperating and organizing people than human animals because they had the empathy to understand the motivations and feelings of others. It is therefore not surprising that Cain would be the one to start bringing them together. Building towns was a key step in the progress of the human race because it enabled individuals to specialize in different roles. An isolated family needed to know how to build a house, breed crops and animals, and invent and create tools, then spend time teaching all this to their children. People in a town could specialize as builders, farmers, inventers, artisans, and teachers.

       So we aren’t surprised when Genesis says about Cain’s descendants that “Jabal … was the father of those who live in tents and raise livestock. … Jubal … was the father of all who play stringed instruments and pipes. ... Tubal-Cain … forged all kinds of tools out of bronze and iron” (Gen 4:20-22). In fact, we would expect Cain’s children to fare much better than the children of others because his family carried the inheritance from God: a spirit that raised them above the human animals. Even if they didn’t use their new insights to search for and to follow God, their spirit still gave them other advantages.

       It is difficult to imagine what a human would be like without a spirit because presumably they have all died out by now, just as the Neanderthals and Denisovans died out thirty-five thousand years ago. Their spirit gave human beings many minor advantages and two major ones. First, they would be aware of God and be able to call on him for help and guidance. Second, they would be much better at cooperating with their fellows. This was really important in times of famine or other problems when only those who stuck together would survive. And sometimes a colony would only survive because individuals were willing to sacrifice themselves for the sake of unrelated fellow humans. This is something you are much more willing to do if you believe that fellow humans are all children of God and that there is life after death – concepts that are related to possessing a spirit.

No conflict

The suggestion that many human animals lived at the time of Adam might seem shocking at first, but it is important to realize that this is not contrary to the text of Genesis – it is only contrary to our traditional interpretation of it. In fact, it makes better sense of some aspects of the text, especially with regard to Cain. Breeding with this other type of human sounds wrong at first – although perhaps not as wrong as marrying a sister. And breeding with these outsiders conferred the advantage of a wider gene pool, something that is now important to us.

       Cain didn’t marry a Neanderthal, because they are likely to have been long extinct. However, some humans had bred with them, so their genes were mixed into the human race. If Cain and his descendants married human animals outside Eden, their children would gain a double advantage – of being spiritual (through Cain and Adam’s side of the family) and of having a superb immune system from the side whose ancestors had bred with Neanderthals.

       The wide variety that consequently exists in the human gene pool means that we have been able to adapt to almost every environment on earth – from the unending heat of the tropics to the barren cold of the poles and the oxygen-depleted heights of the Andes. Our children can be very different: athletic, nerdy, exploring, nurturing, combative, or caring. Not only has this diversity enabled me to inherit unusual health, but it has given the whole of humanity a healthy gene pool which helps us to survive. This was surely part of God’s plan when he made us as part of his creation. He arranged for us to inherit benefits from all of our ancestors, not just from Adam. However, Adam has given us all a most important legacy: our spirit that can communicate with God, and (unfortunately) our sinful rebelliousness.


• Humans benefit from a wide gene pool with much more variety than one recent couple could supply.
• The Bible does not rule out “human animals” that lived without the spirit that was in the “human beings” descended from Adam.
• These human animals would be less capable of empathy and cooperative, so their descendants were less likely to survive.
• Proposal: Cain and others widened the gene pool by breeding with humans outside Eden, and all descendants of Adam were born with a spirit.

1^ See Helen Briggs, “Neanderthal Genes ‘Boosted Our Immunity,’” BBC News, January 7, 2016 (
2^ See Wikipedia, “ABO Blood Group System” (
3^ See Wikipedia, “Gene Polymorphism” (
4^ See Wikipedia, “Mutation Rate” (
5^ See Laure Ségurel, “The ABO Blood Group Is a Trans-Species Polymorphism in Primates,” Proceedings of the National Academy of Sciences of the USA 109 (November 6, 2012): 18493-98 (
6^ See also chap. 17, “What Does the Human Spirit Do?”
7^ See chap. 15, “Made from Dust, Like Adam.”

This was previously published in a similar form in Christianity magazine

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