# Statistical Challenges with Making Super IQ babies

This is a critique of  on LessWrong.

**Disclaimer:** I am not a geneticist, and I've tried to use as little jargon as possible. However, I used the word mutation as a stand-in for SNP (single nucleotide polymorphism, a common type of genetic variation).

## Background

The Superbabies article has 3 sections: why, how, and other. They show:

1.  We should do this, because the effects of editing will be big.
2.  How: Explain how embryo editing could work, if academia was not mind killed (hampered by institutional constraints).
3.  Other: like legal stuff and technical details.

Here is a quick summary of the "why" part of the original article articles arguments, the rest is not relevant to understand my critique.

1.  We can already make (slightly) superbabies selecting embryos with "good" mutations, but this does not scale as there are diminishing returns and almost no gain past "best of 40".
2.  They show that when you edit, you don't have the issue outlined above, because each edit helps, here the only source of diminishing returns is that you pick the most important mutations first.
3.  Then they switch from IQ to a disease focus by removing bad mutations. They also show that most diseases risk can be reduced 50-100% by 3-25 mutations, but if you swap from disease association to life expectancy, then 300 edits may only gain you 14 years, interestingly it only take 16 edits to get the first 5 years.
4.  They show that there are less tradeoffs between mutations than one might initially anticipate, the correlations are mostly positive, ie, curing one disease might protect you from another one.
5.  Then they use chicken becoming 4 times larger over 50 years, which is 40 standard deviation! to motivate the intuition that a species can go out of equilibrium, using selective breeding, so selective editing should allow us to push even further.
6.  Finally, they make theoretical curves for IQ gain and longevity, under the assumption that if we had more data, we could more and better mutations to edit if we had stronger data.

## My Position

At a high level, I appreciate the effort in the original post and think most of it is well-written. The main points about the difference between editing and selecting, the parts about diseases, and to some extent longevity, are valid. However, I am skeptical of the claimed IQ effects.

My critique can be broken down into the following subtopics:

1.  Correlation vs. Causation
2.  The additive assumption of genetics
3.  Regression towards the mean

I'm less skeptical about disease prevention through genetic editing because some powerful examples exist—like how a single edit can reduce Type 2 diabetes risk by half. This suggests a likely causal relationship rather than just a socioeconomic correlation. The additive assumption is also less problematic when dealing with a small number of high-impact edits. In contrast, IQ appears to be influenced by more than 1,000 genetic variations, most predicted to have much smaller effects than +1 IQ point.

## Correlation vs. Causation

This point was mostly raised by  and  and others in the comments to the original post. The issue here is that we only have traits such as IQ and mutations, and thus any relation between the two could be spurious. For example, a mutation might be shared between people who don't like living in old buildings, and thus the causal path runs through lower exposure to leaded paint and asbestos.

While I think the association critique of the baby IQ effects is a very strong argument, I will set that aside for the remainder of this post and focus more on the model assumptions baked into their extrapolations.

It is important to note that when the authors say, "we take into account uncertainty about which of a cluster of nearby genetic variants is actually CAUSING the observed effect."

The more clear wording would be "we take into account uncertainty about which of a cluster of mutations is actually causing the observed association." The latter phrase should also be used if the data needs to be weighted. A simple example of this is the concept of "基因组剪切" (cut and paste) where each cut serves as a source of information to be used to infer another cut, but each cut is also dependent on the cuts of other mutations in the same region. This creates a dilemma where it's difficult to estimate the true effect size due to the correlation between different mutations in the same region.

The authors used a sophisticated statistical method called 'spike-and-slab' that essentially sorts genetic effects into two categories: tiny effects that are probably just noise (the 'spike' at zero) and larger effects that are likely real but might still be overestimated (the 'slab'). This method can adjust differently for simple traits versus complex ones like IQ.

## Optional: Regression towards the null part 2

This section tries to explain why the spike and slap method is insufficient. It assumes a higher familiarity with math than the rest of the post.

A nice feature of the spike-and-slab prior is that it is refitted for each association, so a different spike-and-slab prior will be estimated for the disease explained by 5 mutations and for IQ. This would allow us to have a different level of shrinkage in the square roots of the effects.

There is, however, one issue with the spike-and-slab prior. The more effects you put into the "spike" part, the larger effects are left to be modeled by the "slab" part, creating a dual paradox:

1.  The stronger you believe in a lot of null effects, the more confident you are that the rest of the effects are perfectly fine, because the slab becomes wider when the medium-sized effects are moved to the spike.
2.  The biggest discontinuity is applied at the threshold between spike and slab. Imagine we have mutations that before shrinkage have the values +4 IQ, +2 IQ, +1.9 IQ, and 1.95 is our spike vs. slab cutoff. Furthermore, let's assume that the slab shrinks 25% of the effect. Then we get 4→3, 2→1.5, 1.9→0, meaning we penalize our +2 IQ mutation much less than our +1.9 mutation, despite their similar sizes, and we penalize our +4 IQ effect size more than the +2 IQ effect size, despite it having the biggest effect, this creates an arbitrary cliff where similar-sized effects are treated completely differently based on which side of the cutoff they fall on, and where the one that barely makes it, is the one we are the least skeptical off."

Ideally, we would use a fat-tailed prior (like a t distribution or Cauchy distribution), which would allow for big effects, and shrink small effects a lot. With most fat-tailed priors, there is an inflection point, after which, the further you get away from 0, the less you are shrunk. In this case, the +2 IQ mutation would end up with the least shrinkage, if it is above the inflection point.

In summary, the statistical methods used to estimate genetic effects on IQ likely don't fully account for this 'winner's curse' problem, potentially making the projected benefits of gene editing for intelligence overly optimistic, beyond the issues of causality and additivity. Andrew Gelman has a scalable method where you can convert every effect into a signal-to-noise ratio, but this is highly math-intensive and I am not familiar with it.

1.  The biggest discontinuity is applied at the threshold between spike and slab. Imagine we have mutations that before shrinkage have the values +4 IQ, +2 IQ, +1.9 IQ, and 1.95 is our spike vs. slab cutoff. Furthermore, let's assume that the slab shrinks 25% of the effect. Then we get 4→3, 2→1.5, 1.9→0, meaning we penalize our +2 IQ mutation much less than our +1.9 mutation, despite their similar sizes, and we penalize our +4 IQ effect size more than the +2 IQ effect size, despite it having the biggest effect, this creates an arbitrary cliff where similar-sized effects are treated completely differently based on which side of the cutoff they fall on, and where the one that barely makes it, is the one we are the least skeptical off."
2.  There isn't any hard effect size cutoff like this in the model. The model just finds whatever configurations of spikes have high posteriors given the assumption of sparse normally distributed nonzero effects. I.e., it will keep adding spikes until further spikes can no longer offset their prior improbability via higher likelihood (note this isn't a hard cutoff, since we're trying to approximate the true posterior over all spike configurations; some lower probability configurations with extra spikes will be sampled by the search algorithm).

## Final Note

Lastly, the post discusses "how much IQ" we could improve per edit if we had more data, where they sort of assume that if they had more data, they could find edits with stronger effects. However, it may also be the case that if they had more data, they would see that the real effects are actually smaller. For example, genetic intelligence has been evolving rapidly over human evolution, right up to recent evolutionary history. So difficulty-of-improving-on-a-system-already-optimized-by-evolution isn't that big of a barrier here, and we should expect to see plenty of beneficial variants which have not yet reached fixation just by virtue of evolution not having had enough time yet.

There's probably other kinds of evidence as well; this isn't a topic I've studied much. I like Heyes' cognitive gadgets theory, and genetic factors don't directly produce intelligence but rather interact with cultural infrastructure to shape learning processes. This suggests the most valuable genetic variants might not directly enhance raw processing power but instead improve how effectively our brains interface with cultural tools—essentially helping our brains better leverage the extraordinary cultural inheritance (language among other things) we already possess.

## Longer

### In the modern era, the fertility-IQ correlation seems unclear; in some contexts, higher fertility seems to be linked with lower IQ, in other contexts with higher IQ.

I have no idea of what it was like in the hunter-gatherer era, but it doesn't feel like an obviously impossible notion that very high IQs might have a negative effect on fertility in that time as well.

### E.g. because the geniuses tended to get bored with repeatedly doing routine tasks and there wasn't enough specialization to offload that to others, thus leading to the geniuses having lower status. Plus having an IQ that's sufficiently higher than that of others can make it hard to relate to them and get along socially, and back then there wouldn't have been any high-IQ societies like a university or lesswrong.com to find like-minded peers at.

### If humans are the stupidest thing which could take off, and human civilization arose the moment we became smart enough to build it, there is one set of observations which bothers me:
1.  The Bering land bridge sank around 11,000 BCE, cutting off the Americas from Afroeurasia until the last thousand years.
2.  Around 10,000 BCE, people in the Fertile Crescent started growing wheat, barley, and lentils.
3.  Around 9,000-7,000 BCE, people in Central Mexico started growing corn, beans, and squash.
4.  10-13 separate human groups developed farming on their own with no contact between them. The Sahel region is a clear example, cut off from Eurasia by the Sahara Desert.
5.  Humans had lived in the Fertile Crescent for 40,000-50,000 years before farming started.

### Here's the key point: humans lived all over the world for tens of thousands of years doing basically the same hunter-gatherer thing. Then suddenly, within just a few thousand years starting around 12,000 years ago, many separate groups all invented farming.

### I don't find it plausible that this happened because humans everywhere suddenly evolved to be smarter at the same time across 10+ isolated populations. That's not how advantageous genetic traits tend to emerge, and if it was the case here, there are some specific bits of genetic evidence I'd expect to see (and I don't see them).

### I like Bellwood's hypothesis better: a global climate trigger made farming possible in multiple regions at roughly the same time. When the last ice age ended, the climate stabilized, creating reliable growing seasons that allowed early farming to succeed.

### If farming is needed for civilization, and farming happened because of climate changes rather than humans reaching some intelligence threshold, I don't think the "stupidest possible takeoff" hypothesis looks as plausible. Humans had the brains to invent farming long before they actually did it, and it seems unlikely that the evolutionary arms race that made us smarter stopped at exactly the point we became smart enough to develop agriculture and humans just stagnated while waiting for a better climate to take off.

### For example, "bigger brains" might also not have been the adaptation that enabled agriculture.

### If you have a mutation that gives you +10 IQ that doesn't make it hard for you to relate with your fellow tribe of hunter-gatherers.

### There's a lot more inbreeding in hunter-gatherer tribes that results in mutations being distributed in the tribe than there is in modern Western society.

### The key question is whether you get more IQ if you add IQ-increasing mutations from different tribes together, I don't think that it being disadvantageous to have +30 IQ more than fellow tribe members would be a reason why IQ-increasing mutations that are additive should not exist.

### If you have a mutation that gives you +10 IQ that doesn't make it hard for you to relate with your fellow tribe of hunter-gatherers.

### There's a lot more inbreeding in hunter-gatherer tribes that results in mutations being distributed in the tribe than there is in modern Western society.

### The key question is whether you get more IQ if you add IQ-increasing mutations from different tribes together, I don't think that it being disadvantageous to have +30 IQ more than fellow tribe members would be a reason why IQ-increasing mutations that are additive should not exist.

### If you have a mutation that gives you +10 IQ that doesn't make it hard for you to relate with your fellow tribe of hunter-gatherers.

### There's a lot more inbreeding in hunter-gatherer tribes that results in mutations being distributed in the tribe than there is in modern Western society.

### The key question is whether you get more IQ if you add IQ-increasing mutations from different tribes together, I don't think that it being disadvantageous to have +30 IQ more than fellow tribe members would be a reason why IQ-increasing mutations that are additive should not exist.

### If you have a mutation that gives you +10 IQ that doesn't make it hard for you to relate with your fellow tribe of hunter-gatherers.

### There's a lot more inbreeding in hunter-gatherer tribes that results in mutations being distributed in the tribe than there is in modern Western society.

### The key question is whether you get more IQ if you add IQ-increasing mutations from different tribes together, I don't think that it being disadvantageous to have +30 IQ more than fellow tribe members would be a reason why IQ-increasing mutations that are additive should not exist.

### If you have a mutation that gives you +10 IQ that doesn't make it hard for you to relate with your fellow tribe of hunter-gatherers.

### There's a lot more inbreeding in hunter-gatherer tribes that results in mutations being distributed in the tribe than there is in modern Western society.

### The key question is whether you get more IQ if you add IQ-increasing mutations from different tribes together, I don't think that it being disadvantageous to have +30 IQ more than fellow tribe members would be a reason why IQ-increasing mutations that are additive should not exist.

### If you have a mutation that gives you +10 IQ that doesn't make it hard for you to relate with your fellow tribe of hunter-gatherers.

### There's a lot more inbreeding in hunter-gatherer tribes that results in mutations being distributed in the tribe than there is in modern Western society.

### The key question is whether you get more IQ if you add IQ-increasing mutations from different tribes together, I don't think that it being disadvantageous to have +30 IQ more than fellow tribe members would be a reason why IQ-increasing mutations that are additive should not exist.

### If you have a mutation that gives you +10 IQ that doesn't make it hard for you to relate with your fellow tribe of hunter-gatherers.

### There's a lot more inbreeding in hunter-gatherer tribes that results in mutations being distributed in the tribe than there is in modern Western society.

### The key question is whether you get more IQ if you add IQ-increasing mutations from different tribes together, I don't think that it being disadvantageous to have +30 IQ more than fellow tribe members would be a reason why IQ-increasing mutations that are additive should not exist.

### If you have a mutation that gives you +10 IQ that doesn't make it hard for you to relate with your fellow tribe of hunter-gatherers.

### There's a lot more inbreeding in hunter-gatherer tribes that results in mutations being distributed in the tribe than there is in modern Western society.

### The key question is whether you get more IQ if you add IQ-increasing mutations from different tribes together, I don't think that it being disadvantageous to have +30 IQ more than fellow tribe members would be a reason why IQ-increasing mutations that are additive should not exist.

### If you have a mutation that gives you +10 IQ that doesn't make it hard for you to relate with your fellow tribe of hunter-gatherers.

### There's a lot more inbreeding in hunter-gatherer tribes that results in mutations being distributed in the tribe than there is in modern Western society.

### The key question is whether you get more IQ if you add IQ-increasing mutations from different tribes together, I don't think that it being disadvantageous to have +30 IQ more than fellow tribe members would be a reason why IQ-increasing mutations that are additive should not exist.

### If you have a mutation that gives you +10 IQ that doesn't make it hard for you to relate with your fellow tribe of hunter-gatherers.

### There's a lot more inbreeding in hunter-gatherer tribes that results in mutations being distributed in the tribe than there is in modern Western society.

### The key question is whether you get more IQ if you add IQ-increasing mutations from different tribes together, I don't think that it being disadvantageous to have +30 IQ more than fellow tribe members would be a reason why IQ-increasing mutations that are additive should not exist.

### If you have a mutation that gives you +10 IQ that doesn't make it hard for you to relate with your fellow tribe of hunter-gatherers.

### There's a lot more inbreeding in hunter-gatherer tribes that results in mutations being distributed in the tribe than there is in modern Western society.

### The key question is whether you get more IQ if you add IQ-increasing mutations from different tribes together, I don't think that it being disadvantageous to have +30 IQ more than fellow tribe members would be a reason why IQ-increasing mutations that are additive should not exist.

### If you have a mutation that gives you +10 IQ that doesn't make it hard for you to relate with your fellow tribe of hunter-gatherers.

### There's a lot more inbreeding in hunter-gatherer tribes that results in mutations being distributed in the tribe than there is in modern Western society.

### The key question is whether you get more IQ if you add IQ-increasing mutations from different tribes together, I don't think that it being disadvantageous to have +30 IQ more than fellow tribe members would be a reason why IQ-increasing mutations that are additive should not exist.

### If you have a mutation that gives you +10 IQ that doesn't make it hard for you to relate with your fellow tribe of hunter-gatherers.

### There's a lot more inbreeding in hunter-gatherer tribes that results in mutations being distributed in the tribe than there is in modern Western society.

### The key question is whether you get more IQ if you add IQ-increasing mutations from different tribes together, I don't think that it being disadvantageous to have +30 IQ more than fellow tribe members would be a reason why IQ-increasing mutations that are additive should not exist.

### If you have a mutation that gives you +10 IQ that doesn't make it hard for you to relate with your fellow tribe of hunter-gatherers.

### There's a lot more inbreeding in hunter-gatherer tribes that results in mutations being distributed in the tribe than there is in modern Western society.

### The key question is whether you get more IQ if you add IQ-increasing mutations from different tribes together, I don't think that it being disadvantageous to have +30 IQ more than fellow tribe members would be a reason why IQ-increasing mutations that are additive should not exist.

### If you have a mutation that gives you +10 IQ that doesn't make it hard for you to relate with your fellow tribe of hunter-gatherers.

### There's a lot more inbreeding in hunter-gatherer tribes that results in mutations being distributed in the tribe than there is in modern Western society.

### The key question is whether you get more IQ if you add IQ-increasing mutations from different tribes together, I don't think that it being disadvantageous to have +30 IQ more than fellow tribe members would be a reason why IQ-increasing mutations that are additive should not exist.

### If you have a mutation that gives you +10 IQ that doesn't make it hard for you to relate with your fellow tribe of hunter-gatherers.

### There's a lot more inbreeding in hunter-gatherer tribes that results in mutations being distributed in the tribe than there is in modern Western society.

### The key question is whether you get more IQ if you add IQ-increasing mutations from different tribes together, I don't think that it being disadvantageous to have +30 IQ more than fellow tribe members would be a reason why IQ-increasing mutations that are additive should not exist.

### If you have a mutation that gives you +10 IQ that doesn't make it hard for you to relate with your fellow tribe of hunter-gatherers.

### There's a lot more inbreeding in hunter-gatherer tribes that results in mutations being distributed in the tribe than there is in modern Western society.

### The key question is whether you get more IQ if you add IQ-increasing mutations from different tribes together, I don't think that it being disadvantageous to have +30 IQ more than fellow tribe members would be a reason why IQ-increasing mutations that are additive should not exist.

### If you have a mutation that gives you +10 IQ that doesn't make it hard for you to relate with your fellow tribe of hunter-gatherers.

### There's a lot more inbreeding in hunter-gatherer tribes that results in mutations being distributed in the tribe than there is in modern Western society.

### The key question is whether you get more IQ if you add IQ-increasing mutations from different tribes together, I don't think that it being disadvantageous to have +30 IQ more than fellow tribe members would be a reason why IQ-increasing mutations that are additive should not exist.

### If you have a mutation that gives you +10 IQ that doesn't make it hard for you to relate with your fellow tribe of hunter-gatherers.

### There's a lot more inbreeding in hunter-gatherer tribes that results in mutations being distributed in the tribe than there is in modern Western society.

### The key question is whether you get more IQ if you add IQ-increasing mutations from different tribes together, I don't think that it being disadvantageous to have +30 IQ more than fellow tribe members would be a reason why IQ-increasing mutations that are additive should not exist.

### If you have a mutation that gives you +10 IQ that doesn't make it hard for you to relate with your fellow tribe of hunter-gatherers.

### There's a lot more inbreeding in hunter-gatherer tribes that results in mutations being distributed in the tribe than there is in modern Western society.

### The key question is whether you get more IQ if you add IQ-increasing mutations from different tribes together, I don't think that it being disadvantageous to have +30 IQ more than fellow tribe members would be a reason why IQ-increasing mutations that are additive should not exist.

### If you have a mutation that gives you +10 IQ that doesn't make it hard for you to relate with your fellow tribe of hunter-gatherers.

### There's a lot more inbreeding in hunter-gatherer tribes that results in mutations being distributed in the tribe than there is in modern Western society.

### The key question is whether you get more IQ if you add IQ-increasing mutations from different tribes together, I don't think that it being disadvantageous to have +30 IQ more than fellow tribe members would be a reason why IQ-increasing mutations that are additive should not exist.

### If you have a mutation that gives you +10 IQ that doesn't make it hard for you to relate with your fellow tribe of hunter-gatherers.

### There's a lot more inbreeding in hunter-gatherer tribes that results in mutations being distributed in the tribe than there is in modern Western society.

### The key question is whether you get more IQ if you add IQ-increasing mutations from different tribes together, I don't think that it being disadvantageous to have +30 IQ more than fellow tribe members would be a reason why IQ-increasing mutations that are additive should not exist.

### If you have a mutation that gives you +10 IQ that doesn't make it hard for you to relate with your fellow tribe of hunter-gatherers.

### There's a lot more inbreeding in hunter-gatherer tribes that results in mutations being distributed in the tribe than there is in modern Western society.

### The key question is whether you get more IQ if you add IQ-increasing mutations from different tribes together, I don't think that it being disadvantageous to have +30 IQ more than fellow tribe members would be a reason why IQ-increasing mutations that are additive should not exist.

### If you have a mutation that gives you +10 IQ that doesn't make it hard for you to relate with your fellow tribe of hunter-gatherers.

### There's a lot more inbreeding in hunter-gatherer tribes that results in mutations being distributed in the tribe than there is in modern Western society.

### The key question is whether you get more IQ if you add IQ-increasing mutations from different tribes together, I don't think that it being disadvantageous to have +30 IQ more than fellow tribe members would be a reason why IQ-increasing mutations that are additive should not exist.

### If you have a mutation that gives you +10 IQ that doesn't make it hard for you to relate with your fellow tribe of hunter-gatherers.

### There's a lot more inbreeding in hunter-gatherer tribes that results in mutations being distributed in the tribe than there is in modern Western society.

### The key question is whether you get more IQ if you add IQ-increasing mutations from different tribes together, I don't think that it being disadvantageous to have +30 IQ more than fellow tribe members would be a reason why IQ-increasing mutations that are additive should not exist.

### If you have a mutation that gives you +10 IQ that doesn't make it hard for you to relate with your fellow tribe of hunter-gatherers.

### There's a lot more inbreeding in hunter-gatherer tribes that results in mutations being distributed in the tribe than there is in modern Western society.

### The key question is whether you get more IQ if you add IQ-increasing mutations from different tribes together, I don't think that it being disadvantageous to have +30 IQ more than fellow tribe members would be a reason why IQ-increasing mutations that are additive should not exist.

### If you have a mutation that gives you +10 IQ that doesn't make it hard for you to relate with your fellow tribe of hunter-gatherers.

### There's a lot more inbreeding in hunter-gatherer tribes that results in mutations being distributed in the tribe than there is in modern Western society.

### The key question is whether you get more IQ if you add IQ-increasing mutations from different tribes together, I don't think that it being disadvantageous to have +30 IQ more than fellow tribe members would be a reason why IQ-increasing mutations that are additive should not exist.

### If you have a mutation that gives you +10 IQ that doesn't make it hard for you to relate with your fellow tribe of hunter-gatherers.

### There's a lot more inbreeding in hunter-gatherer tribes that results in mutations being distributed in the tribe than there is in modern Western society.

### The key question is whether you get more IQ if you add IQ-increasing mutations from different tribes together, I don't think that it being disadvantageous to have +30 IQ more than fellow tribe members would be a reason why IQ-increasing mutations that are additive should not exist.

### If you have a mutation that gives you +10 IQ that doesn't make it hard for you to relate with your fellow tribe of hunter-gatherers.

### There's a lot more inbreeding in hunter-gatherer tribes that results in mutations being distributed in the tribe than there is in modern Western society.

### The key question is whether you get more IQ if you add IQ-increasing mutations from different tribes together, I don't think that it being disadvantageous to have +30 IQ more than fellow tribe members would be a reason why IQ-increasing mutations that are additive should not exist.

### If you have a mutation that gives you +10 IQ that doesn't make it hard for you to relate with your fellow tribe of hunter-gatherers.

### There's a lot more inbreeding in hunter-gatherer tribes that results in mutations being distributed in the tribe than there is in modern Western society.

### The key question is whether you get more IQ if you add IQ-increasing mutations from different tribes together, I don't think that it being disadvantageous to have +30 IQ more than fellow tribe members would be a reason why IQ-increasing mutations that are additive should not exist.

### If you have a mutation that gives you +10 IQ that doesn't make it hard for you to relate with your fellow tribe of hunter-gatherers.

### There's a lot more inbreeding in hunter-gatherer tribes that results in mutations being distributed in the tribe than there is in modern Western society.

### The key question is whether you get more IQ if you add IQ-increasing mutations from different tribes together, I don't think that it being disadvantageous to have +30 IQ more than fellow tribe members would be a reason why IQ-increasing mutations that are additive should not exist.

### If you have a mutation that gives you +10 IQ that doesn't make it hard for you to relate with your fellow tribe of hunter-gatherers.

### There's a lot more inbreeding in hunter-gatherer tribes that results in mutations being distributed in the tribe than there is in modern Western society.

### The key question is whether you get more IQ if you add IQ-increasing mutations from different tribes together, I don't think that it being disadvantageous to have +30 IQ more than fellow tribe members would be a reason why IQ-increasing mutations that are additive should not exist.

### If you have a mutation that gives you +10 IQ that doesn't make it hard for you to relate with your fellow tribe of hunter-gatherers.

### There's a lot more inbreeding in hunter-gatherer tribes that results in mutations being distributed in the tribe than there is in modern Western society.

### The key question is whether you get more IQ if you add IQ-increasing mutations from different tribes together, I don't think that it being disadvantageous to have +30 IQ more than fellow tribe members would be a reason why IQ-increasing mutations that are additive should not exist.

### If you have a mutation that gives you +10 IQ that doesn't make it hard for you to relate with your fellow tribe of hunter-gatherers.

### There's a lot more inbreeding in hunter-gatherer tribes that results in mutations being distributed in the tribe than there is in modern Western society.

### The key question is whether you get more IQ if you add IQ-increasing mutations from different tribes together, I don't think that it being disadvantageous to have +30 IQ more than fellow tribe members would be a reason why IQ-increasing mutations that are additive should not exist.
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