Q&A with Harpending and Cochran

You are even meaner than Shulman. We don't know how human intelligence evolved and we need to know it in order to answer your question I think. This is where evolutionary psychology and differential psychology (Am I using that term right?) must come together to work this out.

We think that we know a little bit about how to raise intelligence. Just turn down the suppression of early CNS growth. If you do that in one way the eyeball grows too big and you are nearsighted, which is highly correlated with intelligence. BRCA1 is another early CNS growth suppressor, and we speculate in the book that a mildly broken BRCA1 is an IQ booster even though it gives you cancer later. BTW Greg tells me that there a high correlation between IQ and the risk of brain cancer, perhaps because of the same mechanism.

But these ways of boosting IQ are Red Green engineering. (Red Green is a popular North American comedy on television. The hero is a do-it-yourselfer who does everything shoddily.)

On the other hand IQ seems to behave like a textbook quantitative trait and it ought to respond rapidly to selection. We suggest that it did among Ashkenazi Jews and probably Parsis. IQ does not seem to have a downside in the general population, e.g. it is positively correlated with physical attractiveness, health, lifespan, and so on. Do we get insight into the costs of high IQ by looking at Ashkenazi Jews? Do they have overall higher rates of mental quirks? Cancer? I don't know.

HCH

From The 2% Difference, an article by Robert Sapolsky:

Given the outward differences, it seems reasonable to expect to find fundamental differences in the portions of the genome that determine chimp and human brains—reasonable, at least, to a brainocentric neurobiologist like me. But as it turns out, the chimp brain and the human brain differ hardly at all in their genetic underpinnings. Indeed, a close look at the chimp genome reveals an important lesson in how genes and evolution work, and it suggests that chimps and humans are a lot more similar than even a neurobiologist might think.

...

... Still, chimps and humans have very different brains. So which are the brain-specific genes that have evolved in very different directions in the two species? It turns out that there are hardly any that fit that bill. This, too, makes a great deal of sense. Examine a neuron from a human brain under a microscope, then do the same with a neuron from the brain of a chimp, a rat, a frog, or a sea slug. The neurons all look the same: fibrous dendrites at one end, an axonal cable at the other. They all run on the same basic mechanism: channels and pumps that move sodium, potassium, and calcium around, triggering a wave of excitation called an action potential. They all have a similar complement of neurotransmitters: serotonin, dopamine, glutamate, and so on. They're all the same basic building blocks.

The main difference is in the sheer number of neurons. The human brain has 100 million times the number of neurons a sea slug's brain has. Where do those differences in quantity come from? At some point in their development, all embryos—whether human, chimp, rat, frog, or slug—must have a single first cell committed toward generating neurons. That cell divides and gives rise to 2 cells; those divide into 4, then 8, then 16. After a dozen rounds of cell division, you've got roughly enough neurons to run a slug. Go another 25 rounds or so and you've got a human brain. Stop a couple of rounds short of that and, at about one-third the size of a human brain, you've got one for a chimp. Vastly different outcomes, but relatively few genes regulate the number of rounds of cell division in the nervous system before calling a halt. And it's precisely some of those genes, the ones involved in neural development, that appear on the list of differences between the chimp and human genomes.

That's it; that's the 2 percent solution. What's shocking is the simplicity of it. Humans, to be human, don't need to have evolved unique genes that code for entirely novel types of neurons or neurotransmitters, or a more complex hippocampus (with resulting improvements in memory), or a more complex frontal cortex (from which we gain the ability to postpone gratification). Instead, our braininess as a species arises from having humongous numbers of just a few types of off-the-rack neurons and from the exponentially greater number of interactions between them. The difference is sheer quantity: Qualitative distinctions emerge from large numbers. Genes may have something to do with that quantity, and thus with the complexity of the quality that emerges. Yet no gene or genome can ever tell us what sorts of qualities those will be. Remember that when you and the chimp are eyeball to eyeball, trying to make sense of why the other seems vaguely familiar.

It must be simple in some way since it is so heritable. People with IQs of 90 and IQs of 140 both prosper and do fine. although there are lots of statistical differences between two such groups.

Other other hand if we take a trait like "propensity to learn language in childhood" this seems to me to be relatively invariable and fixed and so probably very complex.

Certainly one could breed for IQ and raise the population mean a lot. But what would we be doing to our children? People with 140 IQ seem to do all right but I would worry a lot about the kind of life a kid with an IQ of 220 would have.

Moved to the kibitzing thread.

 Better hunting techniques can significantly raise Malthusian limits. 

First, you have to remember that old-fashioned humans were one predator among many: improved hunting techniques could raise our share of the pot, as well as decreasing other predators' tendency to eat us. Also, modern humans seem to have used carcasses more efficiently than Neanderthals: they had permafrost storage pits and drying racks, so could have preserved meat for long periods. Neanderthals didn't, and I think they must have wasted a lot. Next, moderns used snares, traps, nets, bows etc to catch smaller game not much harvested by Neanderthals: they also made more use of fish and molluscs. And lastly, more plant foods. Altogether, their innovations gave them a larger share of the game, used that share more efficiently, tapped marine resources (lots of salmon in Europe), and harvested resources at a lower trophic level ( plants for example), which are always more abundant.

Hunting to extinction happened in some places, but not everywhere: it hardly happened in Africa at all. It happened most in places with no previous hominid occupation.

Implied population densities are, I think, extrapolations from known hunter gatherers, salted with some archeological info. Estimated densities range from 0.01/km sq to 1/km sq, strongly dependent upon resources. A lot like those of bears. Lower than chimps, probably: but then chimps manage with a lower-quality diet than humans. We're probably not as good at digesting leaves as they are.

Probably you have to consider Pleistocene climate as well: the world was generally nastier - colder, drier, lower plant productivity due to low CO2 levels.

Yikes! This is worse than my PhD orals.

There have been some (tentatively) identified like the 7-repeat version of the D4 dopamine receptor, the serotonin transporter, and others that Greg will be able to dredge up from his memory.

We may have found others but not identified them. Imagine that it would be highly beneficial to have a little bit less of substance s. If so then a mutation that broke the gene producing s would be favored a lot and would sweep until people with two copies of broken s started being born. How likely is it now that two broken copies of s will still work? A lot of the sweeps identified from SNP scans seem to have stalled out at intermediate frequencies (as opposed to going to fixation) suggesting that heterozygote advantage is widespread.

If so the genome wide association studies ought to find them, and they find a lot, many of the findings are not replicable. So after all the above I have no coherent answer to your question!

I would say that it is some sense obvious that higher intelligence is possible, because the process that led to whatever intelligence we have was haphazard (path-dependent, stochastic, and all that) and because what optimization did occur was under severe constraints - some of which no longer apply. Clearly, the best possible performance under severe constraints is inferior to the best possible with fewer constraints.

So, if C-sections allow baby heads to get bigger, or if calories are freely available today, changes in brain development that take advantage of those relaxed constraints ought to be feasible. In principle this does not have to result in people who are damaged or goofy, although they would not do well in ancestral environments. In practice, since we won't know what the hell we are doing... of course it will.

Still, that's too close to an existence proof: it doesn't really tell you how to do it.

You could probably get real improvements by mining existing genetic variation: look at individuals and groups with unusually high IQs, search for causal variants. Plomin and company haven't any real success ( in terms of QTLs that explain much of the variance) but for this purpose one doesn't care about variance explained, just effect size. A rare allele that does the job would be useful. I'd look at groups with high average IQ, but at others also.

There are other possible approaches. If you could error-correct the genome, fix all the mutational noise, you might see higher IQ. You could dig up Gauss and clone him. My favorite idea is finding two human ethnic groups that 'nick' - whose F1 offspring exhibit hybrid vigor.

As for the singularity: I could, I think, make a pretty good case that scientific and technological progress is slowing down.

I have heard discussion about the singularity on the web but I have never had any idea at all what it is, so I can't say much about that.

I do not think there is much prospect for dramatic IQ elevation without producing somewhat damaged people. We talk a lot in our book about the ever-present deleterious consequences of the strong selection that follows any environmental change. Have a look for example at the whippet homozygous for a dinged version of myostatin. Even a magic pill is likely to do the same thing. OTOH scientists don't have a very good track record at predicting the future. Now, I am going to hop into my flying car and go to the office -:)

HCH

Hi Carl:

No word on that yet. They identified regions of the genome where there are (1) deep gene trees in Europe and/or Asia, (2) we share variants with Neanderthals, and (3) these shared variants are absent in Africa, and they found a lot of them. But if some variants in Neanderthals were positively selected in humans very early on then they would have spread through all humanity, and no one has scanned for those yet.

Our favorite candidate is the famous FOXP2 region, without which one has no speech. Every human has it, and the diversity hear it on the chromosome suggests that it is 42,000 years old in humans. Neanderthals have the human version (so far), so a likely scenario is that we stole it from Neanderthals.

HCH

It is an interesting puzzle. This was a secular rise in cognitive test scores well documented in a number of countries during the 20th century. It has stopped and even reversed in the last few decades. There seem to be several pausible ideas out there

One is that social changes have had the effect of "training" people for cognitive tests: more magazines, radio, chatter everywhere, advertising, etc. Hard idea to test. I do fieldwork in Southern Africa. Forty years ago there were no radios in the backcountry, no books, no magazines. Today radio, newspapers, magazines are everywhere. I expect that this changes people a lot but I have no evidence.

Flynn himself thinks nutrition got better but the data are not clear about that. I would favor as an explanation vaccination and antibiotics. Infectious disease and the inflammation associated with it does seem to damage people (Caleb Finch, Eileen Crimmins, others). We have cut the intensity of childhood insults way down everywhere.

My two cents........

That is a big and interesting question. I do not think that evolutionary biology needed more math at all: they would have done better with less I think. The only math needed (so far) in thinking about acceleration is the result that the fixation probability of a new mutant is 1/2N if it is neutral and 2s if it has selective advantage s. The other important equation is that the change in a quantitative trait is the product of the heritability and the selective differential (the difference between the mean of the population and the mean of parents).

The history is that there was a ruckus in the 1960s between the selectionists and the new sect of neutralism, and neutralism more or less won. Selectionists persisted but that literature has a focus on bacteria in chemostats, plants, yeast, and such. Neutralism answered lots of questions and is associated with some lovely math, but as we took it up we (many of us) lost sight of real evolutionary issues.

Milford Wolpoff, in a review of our book in the American Journal of Physical Anthropology points out that his student Dave Frayer collected a lot of data on changes in European skull size and shape that implied very rapid evolution. In other words we "knew it all along" but never paid attention. In fact Cochran and I "knew" it but never put it together with the new findings from SNP chips. John Hawks did, right away.

So fashion rules and we it is difficult to get away from it I suppose.

 There are sub-patterns.   There are facts about natural selection that every plant geneticist knows that few human geneticists will accept without a fight.  I mean, really, Henry, when a prominent human geneticist says " You don't really believe that bit about lactase persistence being selected, do you?" , or when someone even more famous asks "So why would there be more mutations in a bigger population?"  -  their minds ain't right. 

I don't agree with you except a little bit. And there are foragers who do have some low time preference, like on the US Northwest Coast where they harvested lots of salmon that they smoked and stored. Interior Eskimo slaughtered migrating caribou herds and stored the meat by freezing.

But in general forager life has been almost literally hand to mouth. I have spent a lot of wasted time pulling my hair out about this. We have had lots of Bushman employees in the Kalahari, well compensated. We have spent hours pointing out that we would go back to America, they should invest in goats or cattle, build up a herd, so they will have something to live on after we left. Everyone agreed with us, but they minute Aunt Nellie got sick everything was slaughtered. Again and again and again. Aargghh......

Henry

My feeling is that the dichotomy between societies where males are threatening and violent and societies where males are submissive and not threats to each other is the most interesting social dichotomy we have. In some societies where males are threats there is a clear alternative niche like the Berdache on the Great Plains. In urban ghettos with drug dealers and street corner males there is a significant set of males who hold down jobs and, often, bring the proceeds to support their matrifocal families. How much such males reproduce is not clear. A wonderful description of this, with a zany analysis, is (Sharff, J. W. (1981). Free enterprise and the ghetto family. Psychology Today, 15, 41-8.)

There may well be stable distributions lurking in the social system but they are likely different everywhere: that for Bushmen would be quite different from that for Mundurucu.

Rulers do not always leave more descendants than proles. I highly recommend Gregory Clark's "Farewell to Alms", in which he shows that the medieval ruling class in Britain essentially all killed each other and have no descendants today. On the other end peasants and laborers did not reproduce themselves, so almost everyone in the UK today is descended from the medieval gentry, prosperous merchants, and so on.

I don't think it's correct to assume a pure strategy (ie each male is either dominant OR submissive). It might make more sense for males to be able to switch when the opportunity arises from submissive to dominant (a mixed strategy in game theory terms). I think outsider orang-utans can become alphas (adding the distinctive cheek-flaps etc) when they find a group that will let them join, for example.

We do see humans making the same transition (and in the other direction too) when they move between groups, and when opportunities arise.

I think your perception is correct, but I am no expert. I sense that evolutionary psychologists are really interested in human universals: the famous experiments of Tooby and Cosmides go right to that point. Why are we all afraid of snakes? Why are our babies do hard to toilet train? But they generally don't have a lot to say about variation among humans in these traits.

The other sort that you and I both perceive are interested in human diversity and aren't much concerned with the bigger questions of the ev psych people.

No, they don't "play nice" with each other mostly. It is an exaggeration to say that each regards the phenomena of the other as nuisances. They certainly should see different things: C&T see evolved cheater detection in a logic game while psychologists of the London school see G playing itself out in the diversity of correct answers.

The two areas will come together soon: they are already starting. As some of the comments here indicate, we can't really understand what "Neanderthal intelligence" might mean until we understand the evolution(s) of intelligence. We can examine data all day and still have not an iota of insight about that bigger issue.

I am trying to think about the genesis and maintenance of social class and about the dimensionality of class. We know from the biometricians at the end of the nineteenth century that cognitive ability is essentially a single dimension while athletic ability, for example, is multidimensional. I want to start with a pure inductive approach to class in North America and do the same thing with class. Fat chance, I have found, since every time I get started I get sucked back into genetics.

Henry

Too random to have much effect, I should think. And at the same time, not awful enough to reduce the population to the point where drift would become important. Unless we're talking asteroid impacts.

One can imagine exceptions. For example, if alleles that gave resistance to some deadly plague had negative side effects on intelligence, then you'd see an effect. Note that negative side effects are much more likely than positive side effects.

I know of some neat anecdotal exceptions. Von Neumann got out of Germany in 1930, while the getting was good. When a friend said that Germany was oh-so-cultured and that there was nothing to worry about, Von Neumann didn't believe it. He started quoting the Melian dialogue - pointed out that the Athenians had been pretty cultured. High intelligence helped save his life.

I'm also interested in Nanani's question below, with a specific emphasis on human-caused mass death selecting for specific characteristics. For example, the Cambodian purges of intellectuals or the Communist purges of successful businesspeople. Are these too tenuous a proxy for genes to cause long-term change in alleles, or did the Cambodians and Communists do long-term harm to their genetic legacy?

Seconded, but with a request for contrast, if possible, with human-caused mass-death such as invasion by conquering hordes. What effect do such phenomena have at the genetic level wrt cognition, as opposed to cultural or lingustic transmission?

And thank you all for the honor of your invitation.

HCH