In Robert Heinlein’s book Starship Troopers, he mentioned a planet called Sanctuary. It was retarded: given favorable conditions and similar amounts of time, life had not gotten very far. The most advanced animal was a proto-insect, the most advanced plant something like a primitive fern. The explanation given in the book was that the planet had a very low level of natural radiation: with very few mutations, evolution dawdled.
The planet had been settled by humans, who did well. For example, Terran wheat easily displaced the local plants. But a local biologist tells our hero that in the long run, Sanctuary is a trap. The settlers will hardly evolve at all, and eventually – we’re talking the long run – they’ll be obsolete, replaced by fast-changing outsiders.
Heinlein was right on some of this, wrong on more. In other words, he knew a lot more biology than the average science fiction writer. Mutations are indeed the seed corn of adaptive evolution: you have to have some. But we’re pretty sure that radiation is not the only way of producing them, not even the most common way. It takes a lot of radiation to double the mutation rate – something like a lethal dose, way more than you get from background radiation in a lifetime. I’m not sure how well that was understood in 1959.
But assume it anyway. what would happen if people moved somewhere where the mutation rate was far lower?
Their genetic load would decrease with time, assuming that they were still subject to much selection. Today, everybody has hundreds of nicked or broken genes: selection keeps eliminating them, while mutation keeps creating them. The suspicion is that their effect is quite large. This hypothetical population would have fewer and fewer. In a few thousand years, they would lose most of the variants that decrease fitness by 1% or more.
If the theory of mutational load is correct, it wouldn’t be the people of Sanctuary who would have to worry about becoming obsolete.
West Hunter 
It depends on time scale. Sure, the short term effect (first million years or so on a population < 1 million) is favorable for Sanctuary. But what about a billion years later? It only takes a few missed beneficial alleles to make a big difference in the long run. The disease causing variants were never going to fixation, so in the very long run it's the favorable mutations that matter.
He also missed the point that he was on the cusp of humans actively and intelligently controlling mutation.
Cochran, given that we’ll soon be able to sort embryos such that only favorable mutations are included in our own and other species of interest, might Heinlein not ultimately prove to be correct?
“”But we’re pretty sure that radiation is not the only way of producing them, not even the most common way.”
What’s the most common? Uncorrected replication errors?
In 1959 it was known that multi-generation exposure of rodents to very high levels of radiation caused no detectable increase in mutations. At the time, in the face of anti-nuclear fear, this was resolutely ignored by the talking classes: it was not quite a hate fact but something like that.
This family of posts by Greg is hilarious. He is usually fearless, wading into deep water and right back out again. But here he is tippy-toeing around the current idea that we are chewing on like a ballerina. Greg, spit it out! Of course you will be more reviled than Arthur Jensen and Charles Murray together.
Meanwhile I am certainly thinking very hard about how to establish plausible deniability.
Paul Jaminet in the post above is surely correct.
Is it built on the average temperature-mutation rate correlation?
I read it so and its implications blew my mind (in a good way).
Holy cow! That’s brilliant. Obvious possibility in retrospect, but I’ve never seen it proposed before as an explanation of the correlations between latitude and intelligence, longevity, etc.
And incredibly easily testable once whole-genome sequencing comes into wide use…you could just read it off HapMap-style datasets. I am looking forward eagerly to the day when I can genetically engineer my kids to be more clever and fearless than Cochran.
Okay okay wait! I’m still like halfway through Genetics for Dummies.
Their genetic load would decrease with time, assuming that they were still subject to much selection…. In a few thousand years, they would lose most of the variants that decrease fitness by 1% or more.
Are we talking about some untold number of tropically-concentrated mutations reducing local IQs? Have we identified any of these mutations? It’s plausible to me, even if we haven’t.
It is the sort of thing that makes me do the classic double-take. Hitherto I know little about actual mutations that distinguish sub-Saharans from everyone else. They’ve got their sickle-cell carriers protected from malaria; we’ve got our mutants protected from HIV. And, per this theory, our ancestors had countless cousins with harmful mutations whose bloodlines died out for the usual reasons. The sub-Saharans probably did as well, only down there in the bright sun they got recharged with new mutations, poor devils.
Is that about right?
to FredR:
Sure, and have a look at Steve Hsu’s recent post at http://infoproc.blogspot.com/2012/07/rare-variants-and-human-genetic.html . (Does anyone know how to put proper links in comment posts on this blog?) I presume folks here keep an eye on Steve’s blog: if not you should.
This is great fun for me since all the issues and models are precisely what was hot in human genetics in about 1965. Much of it was never resolved and most of it has been forgotten. What does genetic load really mean? What fraction of our ill health and aches and pains is due to mildly deleterious mutation? And so on.
It is like I am young again.
Finns, Yakuts and other Northern latitude people should have less mutations and be genetically healthier. IQ is a sign of genetic health, yet some peoples that live near the Equator (Cantonese, Southern Brahmins) have higher IQs. Maybe a comparative table of the rate of defective births between different peoples may give us an idea of their relative “mutational load”.
The issue has only a historic interest, since soon we all are going to have semi-synthetic genotypes.
PS Sanctuary population is necessarily Rushton’s r selected, that is, have few offspring and invest in them. The oursiders with high mutational rate must be K selected because they need to produce many children to have one or two good ones. Sanctuary people lives longer too. Somebody less lazy then me could try to establish the correlation between r/K and mutation frequency.
You have r and K flipped – r is having more offspring with less investment, K the reverse. — http://en.wikipedia.org/wiki/Ecology#r.2FK-Selection_theory
You are right. Thanks.
Greg — Given that people in advanced societies these days are deferring childbearing as long as possible (which would tend to increase genetic load), and given that advanced medicine means that the number of children people have is no longer strongly coupled to their fitness (which means that genetic load is not being cleared very quickly), how many generations would you expect it to take before the effects of increased genetic load becomes noticeable (in the sense that sample groups from before and after populations would be plainly distinguishable to someone who knew what he was looking for, even if all else were held equal)?
Genetic load seems to matter. First-borns are likely to have higher IQ than second-borns and so on. The older the child, the younger the parents at the time of conception and the smaller their genetic load. With ageing comes DNA degradation and increase in DNA errors. This would explain why oldest children, besides having higher IQ, are known to have better overall genetic fitness – first-born are also less likely to be gay, less likely to express autistic-like traits, and less likely to be schizophrenics.
I wonder if environmental temperature has the implied effect on mutational load. High mutational load would mean an increase in heterozygosity of populations towards the tropics, which is in fact is a testable assumption.
However, in their paper on the genetics of the Amerindians, Reich and Paabo published the numbers associated with the tribal heterozygosity; in fact Amazonian (which is, low-latitude) Amerindians have the lowest degree in heterozygosity and hence the lowest genetic load (similar to the Finish population in Europe, which are high-latitude dwellers) and the high latitudinal tribes (both north and south) have the highest, which somehow refutes the assumption that Hsu and Cochran made.
In this regard Sanctuarians should not count too much on the natural conditions on their planet; if delayed parenthood is a part of their culture, they are doomed to evolve – either to retardation or to a breed of late parents, whose DNA ages at a slower rate.
My recollection is that Judith Harris didn’t find any birth-order effects when she scrutinized the literature, but on the other hand she was focusing on personality differences.
Where is the evidence for mutation rates in mammals varying by temperature? It doesn’t seem to make sense to me, at least for female mammals: internal body temperature is controlled regardless of external temperature. I could see males with external genitalia getting their gametes baked though.
Also, if this were true wouldn’t new-mutation single-gene genetic diseases show strong geographical patterns? I’ve never seen that claimed by geneticists.
Latitude, elevation and the tempo of molecular evolution in mammals,
Len N. Gillman, D. Jeanette Keeling, Howard A. Ross and Shane D. Wright,
Proc. R. Soc. B 2009 276, 3353-3359
Most mutations are thought to occur in males.
I think we’re talking something like 25% higher. That should absolutely show up in de novo lethal mutations, if we had good records in the right places. In a quick look, I couldn’t find much, but probably someone can determine if there is indeed a higher frequency of such things in, say, the Congo. .
I liked that part of Starship Trooper but it still seemed implausible that Heinlein’s character (I suppose it was Johnny Rico doing the thinking?) would have speculated that the Sanctuarians might use dirty-bomb radiation to get a couple of mutations and keep up. Seems like it would make more sense to offer some lucrative jobs to people from other planets, and/or subsidize a few of their own to get jobs off-planet, presumably find spouses, and settle back on Sanctuary.
But then I’m no Heinlein.
Think of it as Evolution in Action or maybe Flynn is just trying to get more p….
That article must not be from the UK. There is a pretty prominent Scottish study in which female were a point ahead of males.
(Naw just kidding, I know it’s from the UK. I just think it’s funny that each time women best men it’s a first … and whenever men best women it never happened.)
I think Greg is mistaken, for two reasons:
1. The Native American Experiment. Native Americans were in a sanctuary of sorts prior to the arrival of Europeans. They had two enormous continents to themselves and there were not too many new diseases. Then the Europeans arrived with their disgusting diseases and their unfair technology and their firewater, and so forth.
2. The residents of Santuary may have lower genetic load, but surely, once they occupy the whole planet, they will unleash an awesome social selection pressure. Over time, they will stabilize on a particular set of social interactions and likely develop hardware support for those interactions. However, they will be susceptible to any humanoid parasite that has the ability to exploit any groups social wiring.
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