Your Genes Are Boring

Donald Trump is convinced that he has “good genes” and has passed them on to his children. When I look at him and his family, I am unsure what he thinks these genes are coding for or why they are “good.”

My impression is that also many other people have a similar idea that they are endowed with some “special genes.” Sometimes they seem to draw the conclusion that, as a gift to the world, they should spread them around and have many children. This is perhaps reinforced by a tautological and meaningless definition of “fitness” as having many descendants, which is then conflated with genes being “good.” If you believe this, of course, you can force your genes through as “good” by having many children.

Not to be misunderstood: I am fine with someone wanting a large family, hopefully because they like children and are good parents to them. But this reason here seems silly to me. At first glance, I would actually see a strong correlation between the supposed “special genes” and a certain type of self-important stupidity. And hence it would rather seem that it were better for the world if these genes were not spread around even more. As I like to quip: If eugenics were true, people who believe in it should probably have no children to save us from their stupidity.

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But then I am skeptical that there are such “Trump genes” and the like. Let me explain. I begin with a simple question: How special are your genes?

It is hard to ascertain the size of the original human population that we are all descended from. There are estimates that range from 100,000 to 300,000 people some 100,000 years ago or earlier. The current estimate for world population is roughly 7.5 billion. So this has been a boost by a factor of roughly 25,000 or even 75,000. If humankind had expanded proportionally — an assumption that is not realistic as I will explain below — that would also be the factor by which any gene that was present only once in the original population would have been boosted, ie. how many people share it. Not particularly special.

However, this is only a first stab. Suppose a gene was already common in the original population 100,000 years or so, then again with a proportional expansion, the factor could be much greater. If ten percent had the gene then, ten percent would have it now, or about 750 million people. But then the assumption of a proportional expansion is not true. Humankind has grown in a skewed way. Some genes probably went missing along the way. This means those that are still around must be more frequent. And many genes must have been boosted many times over.

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We humans developed in Africa where we first expanded, only later did we find the way out. There was apparently a first wave out that did not last, but finally some made it, perhaps 70,000 years ago. This population was very small, probably only a few thousand strong, maybe even only a few hundred. However, their descendants settled the whole world outside of Africa.

This small population has grown to well over 6 billion people. That is by a factor of one million or even more. And with the simplification again that expansion outside of Africa was proportional, that would be also the factor for the boost that a gene would have experienced that was present only once in the population of initial emigrants from Africa. If a gene was already common then, there would be even more than a million people with it now. If that is special, I don’t know.

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But this is still not correct. There is a principle here: If there is a bottleneck, as with the initial emigrants from Africa where a small subpopulation branches off from a larger one, they are a sample of the whole population, but usually not a representative sample. That’s why they tend to have lower genetic diversity. If there is a series of such bottlenecks, then genetic diversity goes down and down. And indeed there were further bottlenecks, eg. when we humans settled Australia and later the Americas, but also in Europe and Asia as I will explain below.

The claim about decreasing genetic diversity is supported by the evidence. In Africa it is highest. The farther you go away from Africa, the lower the genetic diversity. It is lowest in some indigenous populations in South America. So if your ancestors are from Africa you have probably more special genes than if your ancestors are from Europe, which might be a surprise for Donald Trump.

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The emigration of humans out of Africa is not the end of the story, though, about how skewed the growth of humankind has been. There were also further bottlenecks afterwards.

After hunter and gatherers had settled the world, some people got the idea to domesticate animals perhaps 15,000 years ago or somewhat earlier. It happened in different places independently. Herding can support much denser populations, maybe by a factor of 10 or more versus hunter-gatherers. Those populations who adopted the new technology expanded massively and with them the genes they happened to have. Since they were a sample of a larger population, this was another bottleneck.

Some 10,000 years ago, people also discovered how to domesticate plants. It again happened in different places around the world. Full-blown agriculture can support even denser populations, another factor of perhaps 10 versus herders, and of 100 or more versus hunters and gatherers. That boosted genes that happened to be present in populations who adopted the new technology. In many cases, this boost came on top of a boost from the adoption of herding. And that was another bottleneck.

Those populations who adopted herding and then agriculture expanded a lot versus those that did not. It was not only the boost because of higher population density that was now possible, it was also that they could settle in new habitats. They could also expand into regions with a population who had not made the move. The hunter-gatherers there were probably absorbed into the herder cultures and those of agriculturists, herders into agricultural populations.

These events were bottlenecks that further lowered genetic diversity for populations that at the same time also grew massively. This means that those genes that were associated with the technological advances got a much larger boost than those that were not. That holds for practically all people in Europe and Asia and their descendants elsewhere. They share their genes with many millions of people, sometimes even billions.

If you were actually looking for very special genes, you should not only be looking in Africa where the same progress to herding and agriculture also boosted some parts of the population. But you would have to focus on those populations that have remained hunters and gatherers until our times. They have experienced hardly any expansion for a long time and should hence have some very special genes. But for most of humankind, let’s face it: Our genes are as special as the latest meme on Twitter.

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Be careful here: Our thinking is distorted because we assume that those whose populations expanded had somehow “superior” genes and that was the cause for their expansion. But that does not have to be so: Genes can simply tag along with an expansion that goes on because of technological progress, which is a cultural phenomenon.The ubiquity of many genes could hence have no deeper reason than this accidental association. It is a typical misunderstanding to conclude from ubiquity to some advantage a gene conferred because it was “superior.” That does not have to be the case.

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The move to modern industrial societies leads to another boost by a factor of roughly 12 with a range from perhaps 5 to 20. Populations in Europe and some parts of Asia are already through with it, while it is still ongoing in other parts of the world. Some populations are ahead of the curve here, so the boost for the respective genes has been greater so far. Others will catch up later.

All in all, this means that genes in populations in Europe or Asia should be even less special than the boost by one million implies that resulted from an assumption of proportional growth after the initial emigration from Africa. These genes would be present in tens or hundreds of millions of people, perhaps often even billions.

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There is still one objection, though: There were also further mutations over the past 100,000 years, so new genes came into existence and those could be more special. That is certainly true. However, there is a catch.

If you think you have a very special gene because of a mutation over the past 100,000 years, then one conclusion could be that the mutation is rather recent, maybe as recent as this generation. It might be quite random, and it is not clear why it should be “superior” in some sense. There was not enough time for any selectionary boost. If your special gene has been around for a long time, but is still extremely rare, it is perhaps nothing to boast about.

If you think instead the mutated gene was boosted over time because it led to higher “fitness” in the tautological sense of more descendants, you also have to assume that it is somewhat older because that takes some time, perhaps a few millennia with optimistic assumptions. But in this case, you also have to conclude that the gene became very frequent, especially because there was also an additional boost at the same time from the expansions resulting from technological progress. Or in other words: It is not special, but quite common.

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I would say that the confusion here is that people like Donald Trump think that the differences between people are the result of very special genes that each of them have. He has the “Trump” genes, and that is why he is the person he is. He then passes the superior “Trump” genes on to his children.

However, the differences could just result from a different mix of genes that are themselves common, even ubiquitous. If so, the special combination of genes that led to Donald Trump will never return, which is perhaps a great relief for posterity. And if he tries to pass his “special genes” on, he actually diffuses his special mix of frequent genes, contrary to what he thinks he does. It is then also pointless to try and spread your “special genes” around: They are already all over the place!

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Bottom line: What makes you special is probably not the result of having some special genes. Your genes might be so ubiquitous that they are actually boring.