In a special section of Nature on personal genomics, Brendan Maher writes:
This year, three groups of researchers scoured the genomes of huge populations (the largest study looked at more than 30,000 people) for genetic variants associated with the height differences. More than 40 turned up.
But there was a problem: the variants had tiny effects. Altogether, they accounted for little more than 5% of height’s heritability — just 6 centimetres by the calculations above. Even though these genome-wide association studies (GWAS) turned up dozens of variants, they did “very little of the prediction that you [can] do just by asking people how tall their parents are”, says Joel Hirschhorn at the Broad Institute in Cambridge, Massachusetts, who led one of the studies. . . .
There could be scarier and more intractable reasons for unaccounted-for heritability that are not even being discussed. “It’s a possibility that there’s something we just don’t fundamentally understand,” Kruglyak says. “That it’s so different from what we’re thinking about that we’re not thinking about it yet.”
Still the mystery continues to draw its sleuths, for Kruglyak as for many other basic-research scientists. “You have this clear, tangible phenomenon in which children resemble their parents,” he says. “Despite what students get told in elementary-school science, we just don’t know how that works.”
I don’t think it’s so mysterious. My self-experimentation led me again and again to find unsuspected environmental causes for various problems. I believe the answer is this: The heritability estimates were overestimates. As one researcher put it, “Heritability estimates are basically what clusters in families, and environment clusters in families.” Variations in environment make far more difference than variation in genes.
What the researchers “don’t fundamentally understand,” I believe, is their own tendency toward religious thinking — the tendency, shared by all of us, to believe what we’re told regardless of the (lack of) evidence for it. The notion that genes make a big difference in practice is one of those beliefs, repeated endlessly by genetics researchers (James Watson is fond of repeating it), that are supported by poor evidence at best. Obesity, it should be obvious, is an environmental disease if there ever was one. Yet Jeffrey Friedman, a researcher at Rockefeller University, is studying the genetic basis of obesity.
Thanks to Dave Lull.
This suddenly made me interested in how environmental factors affect height. Any links to further reading/studies on this topic?
I’m a lot shorter than my two younger brothers, and I guess I’m curious as to why it turned out this way.
this is a great article about how environment determines height:
https://www.newyorker.com/archive/2004/04/05/040405fa_fact
Thanks!
Oliver,
I’ve wondered the SAME thing since I’m the shortest among 4 siblings… It’s the nutrition and Weston A Price (as well as the New Yorker article) distinguishes why. My parents were poor as my father was a surgery fellow and new to the U.S. when he arrived from Taiwan, shortly before my conception. I’m Asian but the 3rd and 4th siblings are 5’8′ (and I’m only 5’4.5″ and half-inches are emphasized *hee*).
Grains diminish height — read some WAPF info. Something about the pro-inflammatory and pro-cortisol effects of grains and esp wheat create a metabolic dysregulation which degrades growth and height gains. We went wheat-free in our household in the last 6mos and our children have sprouted in height.
-G
Sorry– I’m the oldest, first born of 4.
Obesity, it should be obvious, is an environmental disease if there ever was one. Yet Jeffrey Friedman, a researcher at Rockefeller University, is studying the genetic basis of obesity.
Bu-bu-but if obesity were an environmental disease, we couldn’t absolve ourselves from personal responsibility. And I for one, won’t stand for that!
Good post.