Dysgenics and mutational load

It seems probable that most variation in health, beauty, and IQ is due to genetic load, large numbers of rare genetic variants. About fifteen percent of the human genome is under negative selection, meaning that in about fifteen percent of the human genome, any random change is likely to be harmful, most variants get eliminated by natural selection in a reasonable time.

The mutation rate in humans is one or two mutations per hundred million bases per generation, probably around one mutation per hundred million bases, for a total of around thirty to sixty mutations per generation, implying around five to nine harmful mutations per generation.

Since we must have been near equilibrium in the ancestral environment, this implies five to nine harmful mutations were eliminated every generation.

This amounts to natural selection working fiercely – that just to stay in the same place we were running mighty fast, that survival of the fittest was pretty harsh.  Since we have not been experiencing severe natural selection since the Industrial Revolution, the number of harmful mutations in the typical individual must have increased by about forty or so.  We must have devolved quite significantly.

Suppose the typical genetic load, the number of harmful mutations that need to be eliminated is n2, so that the variance is around n.

Let us assume that most of these mutations are about equally harmful, which sounds like a silly assumption, but we shall see this assumption matters little.  Let us also assume that they are not very harmful, since the really harmful ones will result in spontaneous abortions or people who have no prospect of reproducing, and the rest of them must be somewhat harmful since natural selection tended to get rid of them in the ancestral environment.

Let us assume that in the ancestral environment, each of these mutations reduced survival chances by a factor of 1- h, h being a very small quantity.

There has not been much natural selection since the Industrial Revolution, so we typically have a lot more harmful mutations than they did, and it is not killing us yet, so h must be quite small, from whence we may conclude that n is quite large, and n2 very large indeed.

So if an individual’s genetic load is N , where N is a quantity close to the average level of n2, his genes have a chance of being represented in the next generation of

(1-h)N-C

Assuming that each harmful mutation reduces survival prospects independently of all of the others.

Where h and C are constant for the species and the environment as a whole, and N is the individuals total genetic load.  At equilibrium, C will be very close to the average genetic load, n2, and N – C is the individual’s genetic load relative to the average successfully reproducing individual.

The mean of N – C is close to zero and the variance in N – C is n.

We are assuming, as seems likely, that most variation is genetic load.

Under realistic assumptions, assuming h is quite small, the number of harmful mutations eliminated in each generation is very close to

h * n2

So, if h is quite small, the genetic load must be very high

Someone entirely free from genetic load would have a quite amazing reproductive success, would be quite godlike.

Assume that in the ancestral environment, seven harmful mutations were eliminated every generation

If a typical mutation reduces fitness (reproductive success) by ten percent, then typical genetic load must be seventy in which case an Adamic individual (no genetic load) would have a reproductive success of fourteen hundred, unity being normal

But ten percent seems quite a lot.  If it was that high, we would be really sick and stupid compared to our Victorian ancestors. Suppose it is more like one percent.  In that case typical genetic load must be seven hundred, in which case an Adamic individual (no genetic load) would have a reproductive success of eleven hundred, unity being normal.  For a mutation rate of seven per generation, and a harmfulness effect of anything substantially smaller than ten percent, mutations accumulate until the load depresses reproductive success by a factor of around eleven hundred or so, which means an individual free from load would be quite extraordinary.  It also means we don’t need to know what the typical harmfulness of a mildly harmful mutation is to judge the genetic load.  The genetic load is proportional to the number of mutations that, in the ancestral environment were routinely eliminated to keep those areas of the genome fairly stable.

Assuming our ancestors were in equilibrium, the typical harmfulness of a mildly harmful mutation does not matter much.  Genetic load must be huge.  If mutations are typically not very harmful, they accumulate to very high levels, so the total harm remains roughly constant independent of the harmfulness of the mutation – and extraordinarily large.  We could not have kept so large a genome free from variation, unless the difference between an Adamic individual, and a regular individual, is huge.

Adamic individuals would all be Einstein combined with Hercules and Genghis Kahn.  To halt our genetic deterioration and improve the race, we can raise the reproduction rate and the death rate, which sounds mighty unpleasant, or we could, if progress continues, solve the problem by genetic engineering.

Could we synthesize a genome free from genetic load?

If we had very high accuracy reads of a very large number of individuals, we could make a pretty good guess as to which variations were genetic load, by determining which variations had survived for many centuries, and which have not.  Having determined what a genome free from load would be, the problem is synthesizing it.

All multicellular animals turn out to have roughly similar genomes, sponges and men, commonly three billion base pairs, organized in chromosomes of around one hundred million base pairs each. There are a few with much more, or much less, but mostly it is something like that.

That is a long way from what the Venter institute can do, but not, perhaps, entirely out of reach. Craig Venter made a working chromosome of one million base pairs.

It is not such a huge leap from booting up a simple microorganism, the simplest possible microorganism, to booting up a human egg. The main difference is that the genome of one is three thousand times bigger than the genome of the other.

It rather looks to me that while progress in reading genes continues, and is accelerating, progress in writing genes has substantially stalled.  The Craig Venter project may represent our high point of genetic engineering achievement, as a man on the moon represents our high point of space travel. It is not obvious that we will be able to produce supermen in time to avoid a dark age of cultural and genetic decline.

Reasonable and foreseeable progress is that we will soon be able to measure the genetic load of a fetus.  We will probably not, however, be able to do anything about it other than selective abortion.

13 Responses to “Dysgenics and mutational load”

  1. Red says:

    Good luck with selective abortion. Our civilization revels in raising retards.

  2. Dan says:

    Here’s from a New Jersey fertility clinic website on the Internet:

    “The shape (morphology) of a sperm is an important determinant of its fertilizability. The egg is enclosed in a protein coat called the zona pellucida (ZP). The ZP performs many functions, but its first task is to select which sperm will fertilize the egg. The ZP bases its selection on the shape of the sperm head. In order to pass through the ZP, the sperm must be vigorously motile and the sperm head must be a symmetrical, oval shape of the appropriate size. Sperm possessing heads that are irregular in shape, too round, too long, too big or too small are prevented from passing through the ZP. It turns out theres a pretty good reason for this. Abnormally shaped sperm often contain abnormal DNA. That is, an abnormally shaped sperm may be short a chromosome or have an extra chromosome or the DNA is packed into the sperm head in such a way so that, if that abnormally shaped sperm were to enter the egg, the DNA would get all tangled up when it tries to form chromosomes inside the egg. Therefore, nature has evolved a way to keep abnormally shaped sperm from getting inside the egg and thereby maximizing the genetic development potential of the embryo.”

    My sense from this is that that plenty of bad mutations get discarded because those sperm don’t get to be the single winner out of millions. Further bad mutations get tossed out through miscarriages, including common miscarriages that occur in the first month.

    And then even if most children that are born manage to survive (and even in the gentlest of societies about 5% won’t live to adulthood due to unavoidable health problems) a good chunk of the population will have reduced fertility for no apparent reason. Many systems have to work well for successful childbearing to occur.

    Finally, attractiveness is a big correlate with health and low mutational load. A man will move heaven and Earth to get a beautiful woman pregnant with his child.

    This is not to say that we are not on a downslope. I don’t know. But perhaps the downslope is not that steep.

    There is just no way that slow-reproducing humans (one child per year under perfect conditions) could ever procreate with the frequency that would be required to fight of genetic decline, especially considering that a good chunk of death has little to do with fitness (e.g. drought that wipes out a crop, or a king killing all rivals to the throne in his family while they are kids.)

    The fact that many genetic defects are selected against in the natural process leading up to birth is evidenced by the horrible success rate of cloning. It takes a lot of tries to get just one clone and even still, clones of farm animals apparently always have freakish genetic defects and never live very long.

    • jim says:

      There is just no way that slow-reproducing humans (one child per year under perfect conditions) could ever procreate with the frequency that would be required to fight of genetic decline,

      Incorrect. If a normal slow reproducing human has a very large genetic load, there will be large variance, so that every failure and death takes out a lot of mildly harmful genes in one go.

      To illustrate this, consider the extreme case:

      Suppose most of the genetic load is genes that reduce survival and reproduction chances by an imperceptibly tiny amount, say one part in ten thousand, a woman very slightly less pretty, a man a millisecond slower with a weapon. More serious mutations get eliminated through miscarriage, or even before conception, as the slow sperm is beaten by his faster and stronger brethren, so we can ignore them.

      Assume there are nine such very slightly harmful mutations per generation.

      Then, at equilibrium in the ancestral environment, total genetic load will be ninety thousand mildly harmful mutations

      Then the variance, the typical difference between two individuals will be three hundred mildly harmful mutations.

      So, instead of one man being a millisecond slower with a knife or a gun than another man, he is three hundred milliseconds slower, which will guarantee he loses the fight horribly. Instead of one woman being fractionally less pretty than another, she is horribly ugly. So if the man is killed in a fight, or the woman winds up alone, instead of taking out one harmful mutation, takes out three hundred harmful mutations in one swoop.

      There is a well known theorem that each harmful mutation takes at least one genetic death to remedy. This would seem to imply that if we have multiple mildly harmful mutations per generation, we should be extinct unless we reproduce like fishes.

      Not so, not what it implies. It implies at least one genetic death relative to an Adamic individual, relative to how someone with no harmful mutations would do. Probably a man with no harmful mutations would live for centuries, be more virile than Genghis Khan, smarter than Einstein, more handsome than Adonis, and stronger than Hercules. A woman with no harmful mutations would probably not hit menopause until her sixties or eighties, would keep her good looks until she was hitting a century, would frequently pop out twins or triplets, and could do so every couple of years starting at eighteen or so if so inclined, which she probably would be, and could raise such a huge family with ease and good humor.

      • VXXC says:

        Can we prove the Adamic individual existed?

        Or is this “settled”?

        • jim says:

          Barring divine or technological intervention, the Adamic individual, the person with few or no downright errors and typos in his genetic code, is merely a theoretical ideal, not a particular person.

          • VXXC says:

            Yes.

            And until we ourselves are divine, we shall bar technological intervention.

            For you see, this thinking is wrong.

            If we wish to end “dysgenic” behavior in our time – the only time we have – then we should simply not subsidize it to begin, and end by not tolerating it. This would be a policy of no state welfare, and laws to match the times. We for instance have English Liberties, we need hence the English Judges. In short criminals are dead as a result of appearing before the bench for any serious offense, or a career of the lesser ones.

            Mere atavism of the common American will return us to brighter skies.

            Intellectuals will take us to new rings of Hell. New rings of Hell being..the Intellectual Atavism. For you see…this is what Intellectuals are: Demons. The 20th century was all theirs, all of it. But Hell on earth began earlier, perhaps even with Luther. Maybe even the Rabbis. But men who think too much hath bought man Hell on earth, always promising Heaven. This is now fact.

            New rings of Hell would be the policy implications of policy based on HBD, dysgenia, the Superman, the Adamic individual, and so on…

  3. Johnny Caustic says:

    A few spots where I think you’re mistaken.

    As Darwin himself pointed out, sexual selection is more powerful than natural selection (under normal, non-crisis circumstances). The Industrial Revolution may have suspended natural selection, but seriously compromised males are still having difficulty reproducing. So your “h” isn’t as small as you imply it is. Of course, sexual selection doesn’t always choose the right thing…there’s the well-known argument that humans are choosing r-selected over K-selected sex partners these days. And since r-selection really is more adaptive until the next big crisis, the very meaning of “h” is ambiguous and changes with the environment.

    Also, Adamic individuals would not be Einstein + Hercules + Genghis Khan. It takes real resources to build men like these, so these men are selected out during times of low resource availability. For instance, men like Hercules are selected out during famines. (While reading “Stalingrad”, I found it interesting that the author took pains to point out that the short, physically unimpressive soldiers were the ones who survived the starvation conditions near the end.) Men with IQs over 150 are weeded out by sexual selection. Highly aggressive men thrive during crises but die at higher rates during peacetime. There are reasons why the bell curves are bell curves. Adamic individuals are probably just humans who are somewhat above average on all the bell curves (especially health).

    • jim says:

      The estimated mutation rate is adult to adult, so ignores those mutations that are eliminated in miscarriage or in the sperm’s race to the egg. So they are all less serious mutations.

      Given that they are not totally deadly, the size of h does not matter much. If h is large, it makes things worse, if h is very small, it does not make things significantly better, because the number of slightly harmful mutations builds up over centuries.

      The eleven hundred factor is what you get with very small h. With quite large h, you get a factor of fourteen hundred or fifteen hundred.

      With several mildly harmful mutations per generation, (1-h)N, h being the effect of the mutation on the probability of successful reproduction, and N the number of mutations at equilibrium in the ancestral environment, is going to be a bit less than one in a thousand, regardless of whether h is large or small. That tells me that the Adamic individual, a person with no genetic load, is going to be dramatically different, godlike.

      The only way to get a different result is to assume a different survival function, that genetic load mutations add up by some different formula to (1-h)N.

      But any reasonable conjecture for adding harmfulness of many mutations of low effect still results in huge differences at equilibrium load between an individual with normal load and no load. There has to be a huge difference for such a high rate of mutation to be eliminated.

      Just has it does not matter much whether h is moderately small or extremely tiny, it does not matter much how the effect of large numbers of mildly harmful mutations combines. Whatever formula you use to estimate reproductive success, it is going to predict that at an equilibrium where a reasonable number of harmful mutations are eliminated every generation, the reproductive success of an individual with much lower genetic load is going to be astonishing and extraordinary.

      This is the converse of the creationist argument that humans, being slower reproducing than fishes, cannot get rid of genetic load, therefore humans must have been created. Well if Adam was pretty much like you and me, the creationist argument follows, but if Adam was remarkable in various ways, among them being such a healthy fellow he lived for nine centuries, then the creationist argument does not follow. If we are already that sick relative to a person with little or no genetic load, then natural selection has enough variance to work with that it can winnow out genetic load fast enough, under tough conditions, so we do not need to assume that Adam existed.

  4. […] It rather looks to me that while progress in reading genes continues, and is accelerating, progress … […]

  5. […] This amounts to natural selection working fiercely – that just to stay in the same place we were running mighty fast, that survival of the fittest was pretty harsh. Since we have not been experiencing severe natural selection since the Industrial Revolution, the number of harmful mutations in the typical individual must have increased by about forty or so. We must have devolved quite significantly. _Dysgenics and Mutational Load […]

  6. […] Since we have not been experiencing severe natural selection since the Industrial Revolution, the number of harmful mutations in the typical individual must have increased by about forty or so. We must have devolved quite significantly. LINK […]

  7. […] Since we have not been experiencing severe natural selection since the Industrial Revolution, the number of harmful mutations in the typical individual must have increased by about forty or so. We must have devolved quite significantly. LINK […]

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