“If you truly believe that the demographics of Hunter represent the distribution of intelligence in this city, then you must believe that the Upper West Side, Bayside and Flushing are intrinsically more intelligent than the South Bronx, Bedford-Stuyvesant and Washington Heights, and I refuse to accept that.”

In a related thread on the blog KitchTableMath, commenter Crimson Wife said:

Richard Nisbett has a long discussion about race & IQ in his book Intelligence and How to Get It. He makes a convincing argument that the differences are mostly environmental (which can be changed) rather than genetic (which obviously can’t). If it were genetic, then IQ in blacks would be positively correlated the degree of white ancestry- and it isn’t.

Well, it is, but never mind. The broader point is that Nisbett is a spirited defender of the politically correct view that racial disparities in IQ result primarily from differences in children’s environments. The implication is that these disparities will mostly vanish if environments become more similar.

That’s more wishful thinking than argument, and it’s “convincing” only to those who already agree with Nisbett’s thesis. But it’s too vast a subject to settle here, so let me just offer a couple of links.

In a May 2009 working paper, J. Philippe Rushton and Arthur Jensen critique Nisbett’s book point by point. If you agree with Nisbett, you won’t agree with them, and vice versa, but if you’re going to write about these things you ought to be familiar with arguments on both sides.

About five years ago, Jensen and Rushton published a paper, “Thirty years of research on race differences in cognitive ability,” Psychology, Public Policy, and Law, 11, 235-294. They do not claim that environment plays no role in cognitive ability — indeed, no one has ever claimed that, as far as they know. Their much more modest claim, that the effect of heredity is greater than zero, is radioactive enough. Remember that Nobel laureate James Watson was hounded from his position for much milder comments, and he didn’t even mention heredity.

That’s one reason so few researchers risk working in this area. But both Rushton and Jensen have already survived that gantlet — Jensen more than 40 years ago — so they have nothing further to fear.

I should add the disclosure that I am slightly acquainted with both men, and admire them, their work, and their determination.

The book’s website has a wealth of material, so I won’t belabor the point, but in brief their argument is that over the last 10,000 years, roughly since the beginning of agriculture — both the domestication of animals and the planting and harvesting of crops — human evolution has been happening faster than it ever did earlier in the history of the species. Faster, as in 100 times faster.

There are two principal, interacting, reasons. First, agriculture allowed people to live in larger and more densely settled groups, which altered the selective pressures influencing reproductive success. Different foods, different diseases, different social expectations — all changed which people were more likely to have children who themselves lived long enough to successfully raise children of their own. Not much more likely, usually, but a very small percentage advantage is powerful enough to sweep a whole population in a lot less than 10,000 years.

Second, agriculture supported a much larger total population, meaning more mutations, more bodies testing whether this version of a gene or that offered better odds in the lottery that pays off in more descendants. And there’s no rule that limits players in the lottery to buying just one ticket. Many different genetic changes may be happening simultaneously in a population.

There’s been plenty of discussion on blogs for you to explore, but you could start with 2blowhards, which did a weeklong series of interviews with Greg Cochran. Check the archives for the week of Jan. 25.

And Steve Sailer has a great review he wrote for VDare. Michael Blowhard calls it “rowdy.” I think I’d go for “rollicking” myself. Sailer writes, “Perhaps my gravestone will read, ‘He introduced Cochran to Harpending.’ ”

The question was prompted, she tells us, by her 3-year-old son, who objected that something he’d been watching on his laptop wasn’t a book, as the computer had described it. “It’s more like a movie or a video,” he said.

Well, yeah, though I think she may be making a bit too much of this. If the child masters the reading code, I’m not sure whether it makes much difference where or how he learns. Yes, college professors complain that their students no longer have the attention capacity to slog through long or difficult texts. But I suspect college professors were saying that long before their students grew up with TV or laptops.

I’d like to draw your attention, however, to a point she made in passing:

In their book “Freakonomics,” Stephen J. Dubner and Steven D. Levitt write that kids who grow up in houses packed with books fare better on school tests than those who grow up with fewer books. But they also contend that reading aloud to children and limiting their TV time has no correlation with success on tests. If both of these observations hold, it’s worth determining what books really are, the better to decisively decorate with them. The widespread digitization of text has complicated the matter. Will Ben benefit if I load my Kindle with hundreds of books that he can’t see? Or does he need the spectacle of hard- and softcover dust magnets eliminating floor space in our small apartment to get the full “Freakonomics” effect? I sadly suspect he needs the shelves and dust.

I haven’t read Freakonomics, though I do like the blog, so I can’t say whether Heffernan has correctly reported what the authors say. And I don’t doubt the first claim, that children who grow up surrounded by books do better on school tests than those who don’t (though I’m not so sure about the next part). What seems odd to me is that she seems to imply the books are the causal factor, to the extent of speculating whether having them in pixels rather than on paper will lessen their influence.

Doesn’t the chief causal argument run like this?

Oh, we all know exceptions to these correlations, but the significant point is that the causal relation doesn’t run backwards. Doing better on school tests won’t make you smarter than you would be if you never took them, though it has other benefits that can amplify the effects of being smarter, in line with Malcolm Gladwell’s example of children who are among the oldest in their cohort when they begin playing hockey. Filling your house with books won’t make you smarter, though reading voraciously may make you more successful than others who start with similar smarts. Having smart children doesn’t retroactively make you smarter, though it might cause people who know you to wonder whether they may have underestimated you.

When I read things like this, I always wonder whether the writer is truly oblivious to what’s in front of her eyes, or whether she just feels it is obligatory to pretend she doesn’t see.

Goldin and Katz make two largely correct diagnostic points in The Race Between Education and Technology; that the United States got a significant head start on economic development because it expanded access to secondary and post-secondary education sooner than other countries, and we are no longer ahead in that regard. Their prescription, however, is largely incorrect. We can’t get ahead of other countries by increasing the number of Americans graduating from college, because nearly all of the students who can do so are already trying.

Joanne Jacobs posted on this in the context of David Brooks’ NYTimes column and I left this comment there:

>>>>
If no European country in 1950 had more than 30 percent of its older teens in school, that was an inefficiency that the United States could exploit to its advantage. But if every young person who can benefit from staying in school long enough to graduate is already doing so, there’s nothing further to exploit.

We can argue about what the ideal high school graduation rate should be, that is, what the criterion for graduation should be, and what needs to be done to ensure every child who is capable of meeting the criterion has resources and opportunity to do so. But it is delusional to believe that we can have both a meaningful criterion for graduation and a 100 percent graduation rate.

I suspect the true graduation rate should be between 80 and 85 percent. Maybe we could push it to 90, subject to the law of diminishing returns, if we poured every possible dollar into the last few marginal students — though, as James Heckman has demonstrated, we’d get much higher returns if we invested the money in them when they were little.

Something similar operates all along the line of returns to increasing education. There are non-economic returns to more education, but they don’t depend on credentials. If everyone who is capable of benefiting economically from higher education is already able to earn a degree, there is no further inefficiency for the U.S. to exploit.

If other countries have larger percentages of their populations who are capable of benefiting from more years of education than the U.S. does, well, what are we supposed to do about that?
>>>>

Brooks cites economist James Heckman in support of early intervention, but Heckman’s point is not that early intervention is a panacea, but that whatever it can accomplish will be most effective if it’s done early rather than late.

I haven’t read the Heckman paper Brooks is citing, but Heckman has said — very circumspectly — that African Americans and Hispanics begin school with similar performance deficits, but that Hispanics are much more likely to make them up.

From a column I wrote:

. . .
“Our analysis of the Hispanic data illuminates the traditional study of black-white differences and casts doubt on many conventional explanations of these differences since they do not apply to Hispanics who also suffer from many of the same disadvantages.”

I know this is contrary to just about everything you’ve heard or read, so you’re asking, “Who are these people?” They’re Pedro Carneiro, University College London; James J. Heckman, University of Chicago, American Bar Foundation and University College London (and winner of the 2000 Nobel Prize in economics for developing the kind of technical statistical analysis that undergirds this paper) and Dimitriy V. Masterov. The paper was written for the Institute for Labor Market Policy Evaluation, a part of the Swedish Ministry of Industry, Employment and Communications, in Uppsala, Sweden.

The paper is “Labor market discrimination and racial differences in premarket factors” and it’s at www.ifau.se/swe/pdf2005/wp05-03.pdf on the Web.

Steve Sailer has written about the Brooks column. See also this post at the population genetics blog gnxp.

(For a bonus, the immediately preceding gnxp post dissects the media coverage of the math/gender study.)

Cowen asks a sample question: How many people are airborne over the United States at any given moment?

Leaving aside for the moment the obvious fact that it matters whether the moment is mid-morning or middle-of-the night, the first thing that occurred to me was that there were around 6,000 planes in the air when the FAA grounded them on 9/11, so — very roughly — 600,000.

One of the commenters at MR also started with the 9/11 figure, though he recalled it as 4,000. Others explained their estimates reasoning from different assumptions; how many runways active at the several NYC airports, how many daily flights out of Logan airport, how much time does the average American spend in the air in a year?

The thing is, that faced with a blank cocktail napkin, you have to start somewhere, and that means having a mind already well furnished with estimates of other numbers that can be combined to come up with a plausible answer for a novel question.

And it’s not just a parlor game. One of the commenters, giving no rationale, said merely, “10,000.” That isn’t plausible — not if you’ve ever been in a major airport on the day before Thanksgiving, or for that matter ever seen pictures of one on the evening news. People in a democracy are constantly being asked to estimate the plausibility of some policy proposal or other, or to judge the credibility of some politician’s estimates. If they have nowhere to start, their judgment isn’t worth much.

Co-author Weinstein dropped in to the MR comments with a couple of other questions:

How big a landfill would we need to store all our trash for the next century? (And what fraction of the US landmass is that?)

Compare the waste generated per kilometer of horse-drawn carriages and of automobiles.

Cowen says, “This book isn’t for everyone but if you think you might like it you probably will.” Sounds about right.

Perhaps, but it would also make sense for Harford to be a trifle more skeptical about biology. He says:

Reading biologist Edward O. Wilson, I discover that in a few dozen generations all human beings will be “the same,” in the sense that whether in London or Shanghai or Moscow or Lagos, the same racial mix would be found. Viewed differently, the variety of human beings would be unprecedented: as this process of racial mixing accelerates, “many more combinations of skin color, facial features, talents, and other traits influenced by genes are now arising than ever existed before.” (The footnote is to p. 304 of Wilson’s book Consilience.)

Why does Harford endorse the notion that the process of racial mixing is accelerating? It’s trivially true that someone can have children with a person of a different race rather more easily now than was possible when the only way to get from one continent to another was to walk or paddle. But does that mean a whole lot of people are going to do it (relative to the size of the population)? How likely is migration on a scale sufficient to homogenize the populations of Lagos and Shanghai? Or preferential intermarriage with the indigenous population rather than with one’s fellow migrants?

The offhand phrase, “a few dozen generations,” is a sign that the writer really couldn’t be bothered to sketch out a few numbers on the back of an envelope. How long is it? Depending on what the meaning of “a few” or “generation” is, around 1,000 years. That hasn’t been long enough to homogenize Paris and Berlin, let alone Iceland and Greece or Africa and China.

What is accelerating is the rate of human evolution that is driving the continental populations apart faster than migration is blending them back together. There will be many more combinations of traits influenced by genetics, as Wilson says, but the likely outcome will be populations that are more geographically distinctive rather than less so, as Harford assumes.

A blockbuster paper published online today by the Proceedings of the National Academy of Sciences turns that old story on its head.

Cultural evolution diversifies the physical environments where humans live, creating a multitude of places where useful mutations can thrive. And greatly increased population density means ever more bodies where mutations may be selected for usefulness.

The result, says Greg Cochran, one of the authors, is that human biological evolution has accelerated, to perhaps 100 times as fast as in prehistory. (And that’s before we had the genetic tools to modify it on purpose.)

I don’t intend to dismiss the other authors; it’s only that Cochran happens to be the one I talked with. The others are John Hawks, Eric T. Wang, Henry C. Harpending, and Robert K. Moyzis. I’ll add a link to the specific article at PNAS as soon as I have one.

UPDATE: Steve Sailer at http://isteve.blogspot.com/ links to the paper at

http://www.anthro.utah.edu/PDFs/accel.pnas.smallpdf.pdf

and also has links to early press coverage at the LA Times, Reuters and elsewhere

Also, lead author John Hawks has further comment about the study on his blog,

http://johnhawks.net/weblog/topics/evolution/selection/acceleration_embargo_ends_2007.html

The old story was that around the time agriculture started to replace hunting and gathering as a way of life for human beings, biological evolution faded into insignificance because it was so much slower. There’s hardly been enough time – only about 10,000 years or so – for human biology to have changed enough so’s you’d notice.

Not so, as studies of the human genome are demonstrating. When people began domesticating animals, planting crops, and living in settled communities, they created environments for themselves quite different from any environments the human species had occupied before, and natural selection proceeded, as it always does, to favor survival and reproductive success for individuals who were, by chance, better adapted to those environments.

The marquee example is retaining the ability to digest milk into adulthood, which is nearly universal among people of European descent, and quite rare elsewhere.

But the shift to agriculture was also important, Cochran said, because agriculture can support a larger population. Any individual might be the next one to draw a winning ticket in the genetic lottery, and the human species was suddenly buying a lot more lottery tickets.

Think of the genes as a crew of thousands of extras, swarming around the sets and the studio lots, auditioning for jobs. They play more than one role, in lots of different movies, for different directors, as circumstances permit.

One day on the set where they’re filming a swords-and-circuses epic, the director spots a spear-carrier who has given an especially elegant performance, impaling a charioteer.

“You there, with the spear? Could you do that again? Yeah?! I’m gonna make you a star!” And – for a quick glimpse into how biology and culture drive each other – if the spear-carrier proves to be bankable, he’ll get more roles, the director will get more movies, the studio will tilt toward making more epics and the extras with good spear-carrying traits will be more likely to succeed in that environment.

Success, in the gene world, is reproductive success – leaving descendants – but given the role of the casting couch in Hollywood, maybe that’s not pushing the metaphor too far.

On the next set over, the director is casting a chick flick. He says to his assistant, “see that looker over there, the one with the purple eyes? Ask her whether she can ride a horse.”

Now the aspiring starlets competing with Elizabeth Taylor for a role in “National Velvet” can take riding lessons. But they can’t do anything to give themselves violet eyes.

The hunter-gatherers competing with pastoralists for food resources could certainly have learned to keep domesticated animals. But if they and their children could not digest milk much past the average age of weaning, it wouldn’t do them any good. In hard times they’d starve while the meek drinkers of milk inherit the earth.

Or at least a broad swath of it from Iceland to South India.

Accelerated biological evolution in humans doesn’t mean that we’re turning into aliens, but there is evidence that hundreds of human genes are under selection pressure, having to do with such things as diet, vitamin metabolism, the functioning of the central nervous system, disease resistance, hair, skin and eye color, the shape of the skeleton and behavioral traits better suited to living in large groups. “We’re tamer,” Cochran said.

I asked him why we’re not developing floppy ears like the silver foxes bred for tameness.

So where is that evidence coming from? In part, from an ambitious international effort called The HapMap Project (www.hapmap.org).

The human genome has about 3 billion base pairs, strung out in long chains in 23 pairs of chromosomes. Between any two people, most of the base pairs will be the same, but researchers estimate there may be some 10 million locations along the chromosomes where variant spellings of the genetic code appear. If you should happen to hear geneticists talking about “snips,” that’s what they mean; it’s short for “single nucleotide polymorphism.”

The HapMap project is intended to make that vast amount of information more manageable so medical researchers can more efficiently go looking for genes that may influence health. “Genetic variants that are near each other tend to be inherited together,” the HapMap site explains. “These regions of linked variants are known as haplotypes” (hence the name).

A relatively small number of “tag” SNPs is enough to uniquely identify a haplotype, and if researchers know what those are, they don’t need to look at every base pair.

Because chromosomes are typically cut apart into several pieces and reassembled during reproduction, it is approximately correct that the longer a haplotype is, the younger it is. So the HapMap serves as a genetic clock for the species.

The ability to digest lactose goes back roughly 8,000 years. Hey, useful mutations don’t always come along just when you want them. Malaria resistance begins to appear about 5,000 years ago.

Most haplotypes are old, and found in almost every human population, though not necessarily with the same frequency. But the clocks in different places started at different times and they’re not all running at the same speed. The HapMap project is studying three groups of 90 people each, one from the Yoruba tribe in Nigeria, one from East Asia (Tokyo and Beijing) and one of Americans of northern European descent. All the groups have numerous genes under selection, but not all the same ones. If the evolutionary price of resistance to malaria is sickle-cell anemia, it is far too high a price to pay for populations living where it’s too cold for malarial mosquitoes anyway. If the evolutionary price of light skin is melanoma, the price is too high in equatorial Africa.

You understand there is no agency or designer deciding these things. There’s just a small statistical advantage in each generation for those with a more favorable version of a gene, “favorable” meaning only that children in that environment who inherit it are slightly more likely to grow up and have children themselves than those who don’t. Researchers might not even know which gene in a haplotype is being selected for, or what it does.

They do know, though, that it’s happening faster than we used to think. Cochran said, according to a press release from the University of Utah, “History looks more and more like a science fiction novel in which mutants repeatedly arose and displaced normal humans – sometimes quietly, by surviving starvation and disease better, sometimes as a conquering horde. And we are those mutants.”

The BBC reported that the Science Museum where he was to speak canceled the event. And today the BBC is reporting that he has been suspended from his job as chancellor of the Cold Spring Harbor Laboratory on Long Island, New York.

The message is unmistakable: “You can’t say that!” And never mind whether it might be true and what such an inconvenient truth might mean for wise policy decisions.

Watson has also written, “There is no firm reason to anticipate that the intellectual capacities of peoples geographically separated in their evolution should prove to have evolved identically. Our wanting to reserve equal powers of reason as some universal heritage of humanity will not be enough to make it so.”

“No firm reason” indeed, and substantial empirical evidence that it is false. And globally, the issue concerns not just Africans and “Westerners” — which means people largely of European descent, although nobody is allowed to say that, either — but Africa and Asia. The same kind of evidence suggests that East Asians on average are smarter than both the other groups (but it’s apparently all right to mention that).

The news stories, as is only to be expected, are not familiar with the science, and get it wrong. The BBC wrote, “When, some 40 years later, scientists were finally able to read all of the DNA in our cells they were able to show that there was no genetic basis for the concept of race.”

No, that’s not what they showed. On the contrary, genetic markers are very effective at identifying an individual’s geographic ancestry, and getting better all the time. That’s not identical to race, which does have social aspects in addition to biological ones, but the match is pretty close.

And the BBC continues, “People from different racial groups can be more genetically similar than individuals within the same group. Genetic studies show that there is more variability in the gene pool in Africa, than outside.”

That’s true, but it is entirely irrelevant. Men and women can be more genetically similar (differing only in the few genes on the Y-chromosome) than two males or two females, but that does not imply there is no distinction between males and females.

The evolution blog Gene Expression links to the original articles.

One resident confidently assured us that replacing ordinary salt with sea salt would not only prevent the ill effects of excessive salt in the diet, but actually reverse them.

I should have thought to ask, does that mean that drinking sea water instead of fresh would be good for one’s health? But never mind; she’ll say it again another day and I’ll ask her then.

Another resident offered her contribution to children’s health, a little jingle she taught her own children.

“The more white bread, the sooner dead,” she said. “They remembered that.”

I’ll bet they did.

An article in the Sept. 16 New York Times Magazine offers a whisper of explanation for why different people hold conflicting views about what’s good for your health; at different times, the medical establishment does too.

In “Do We Really Know What Makes Us Healthy?” Gary Taubes explains why the answer is often “No.”

His marquee example is hormone replacement therapy, prescribed not merely to alleviate the symptoms of menopause, but for long-term use as a way to decrease the risks of heart disease and osteoporosis. A report released in 1985 by the long-running and eminently respectable Nurses’ Health Study said that women in the study who were taking estrogen had only a third as many heart attacks as those who had never taken it.

That was good enough reason for many doctors, including mine, to prescribe it even for women who didn’t have symptoms associated with menopause.

But the nurses’ health study was an observational study, that is, one that enrolls thousands of people and surveys and measures them regularly for information about anything anyone can think of that might be relevant to their health. If something possibly significant pops out of the data, such as a two-thirds reduction in heart attacks, then other researchers go and set up clinical trials, with two groups of people, one of which gets the treatment being tested and the other does not, and neither the patients nor their doctors know which group a patient is in.

Clinical trials take a long time to do, and though there were indications along the way that something was wrong, in 2002 a study by the Women’s Health Initiative concluded that hormone replacement therapy “constituted a potential health risk for all postmenopausal women. While it might protect them against osteoporosis and perhaps colorectal cancer, these benefits would be outweighed by increased risks of heart disease, stroke, blood clots, breast cancer and perhaps even dementia,” Taubes says.

Hormone replacement therapy is not the only medical practice whose supposed benefits, as suggested by the nurses’ study, were not confirmed in clinical trials. Others are antioxidants, vitamins, low-dose aspirin and folic acid (see the article for more specific detail).

It’s not only the residents of Millstream Commons who believe things about their health that aren’t so. Sometimes their doctors do too.

Linda Seebach is an online columnist who blogs at www.lindaseebach.net