On a good day, I’m 5′ 7″. (I prefer to think of myself as compact but made of premium materials.) That makes me about the same height as economist John Komlos of the University of Munich, who is at the heart of Nancy Shute’s recent NPR report about how Americans’ stable stature may reflect reflect shortcomings of its healthcare:
Through most of American history, we’ve been the tallest population on the planet. Americans were two inches taller than the Englishmen they fought in the Revolutionary War, thanks to abundant food and a healthy rural life, far from the disease-ridden cities of Europe.
But we’re no longer at the top. Northern Europeans are now the world’s tallest people, led by the Dutch. The average Dutch man is 6 feet tall, while the average American man maxes out at 5-foot-9.
Good health care and good nutrition during pregnancy and early childhood are two reasons why the Dutch have grown so tall, Komlos says. In addition, the Dutch guarantee equal access to critical resources like prenatal care. That’s not the case in the United States, where 17 percent of the population has no health insurance.
When I first heard the suggestion that economic inequality and inadequacies of health care in the U.S., my skepticism antennae went up. Surely it couldn’t be that simple, I thought. After all, the past few decades have seen a big influx of immigration to the U.S. from Latin America and Asia; perhaps incoming shorter populations were masking growth in U.S. stature that would otherwise be apparent.
But that is not the case. Shute’s article was anticipated in 2004 by Burkhard Bilger’s fantastic article in The New Yorker, which is vastly more thorough (natch!) and anticipated exactly this objection—as, one would hope, Komlos himself would and did:
The obvious answer would seem to be immigration. The more Mexicans and Chinese there are in the United States, the shorter the American population becomes. But the height statistics that Komlos cites include only native-born Americans who speak English at home, and he is careful to screen out people of Asian and Hispanic descent. In any case, according to Richard Steckel [of Ohio State], who has also analyzed American heights, the United States takes in too few immigrants to account for the disparity with Northern Europe.
By all means, read Bilger’s New Yorker piece in its entirety, which makes the case for simple height measurements as an indicator of populations’ average health and explains some of the fascinating insights it offers into the roller-coaster history of Northern European size (which plummeted from the time of Charlemagne until the 17th century, then started upward again), the treatment of slaves on American plantations, and the effects of industrialization worldwide. Even if you’re still leery (as I am) about using height this way—and about the meaning of the U.S.-Dutch comparison in particular—you’ll find the story provocative and rewarding.
Let me break out one particular point in Bilger’s article because of how it illuminates another, even more contentious issue: intelligence. Bilger writes:
In the nineteenth century, when Americans were the tallest people in the world, the country took in floods of immigrants. And those Europeans, too, were small compared with native-born Americans. Malnourishment in a mother can cause a child not to grow as tall as it would otherwise. But after three generations or so the immigrants catch up. Around the world, well-fed children differ in height by less than half an inch. In a few, rare cases, an entire people may share the same growth disorder. African Pygmies, for instance, produce too few growth hormones and the proteins that bind them to tissues, so they can’t break five feet even on the best of diets. By and large, though, any population can grow as tall as any other.
What’s noteworthy about this observation that the varying heights of populations are not limited primarily by their genetic differences is that the best estimates peg the heritability of height at around 80 percent. That is, within a population in a consistent environment, 80 percent of the variation in height owes to genetic factors. (Or if you prefer, your parents’ height was 80 percent predictive of your own because their height suggested how much your height might vary from the mean.) In the case of height, those genetic factors are still rather obscure—a Nature Genetics paper published last summer suggested that tiny nudges might be scattered throughout the genome rather than concentrating within a few clearly identifiable “tallness” or “shortness” alleles. But whatever the case, two facts are undeniable: (1) a genetic signal in height is undeniable, and (2) environmental influences can swamp—not erase, but overwhelm—the variation otherwise attributable to genetics, which is why the traditionally short Japanese are nearly the height of Americans now and we are nine inches taller than the Frenchmen who stormed the Bastille.
Remember this the next time you read about the genetics of I.Q. and the arguments that are framed around differences in intelligence between races or other population groups. The heritability of I.Q. can be hard even to define (read this lengthy but worthwhile post by Cosma Shalizi to understand why) but good estimates often place it at around 50 percent—well below that of height. Environmental influences on I.Q. should therefore be huge, and one should be very skeptical of arguments that imply (or state outright) that any alleged differences between those groups are innate or unchangeable. Indeed, if Komlos and his colleagues are right that differences in health care explain the plateau in U.S. height, one might expect that those same health care differences—which certainly correlate with economic status and race in this country—could have a very marked effect on I.Q., too.