Height Puzzle

Among adults of industrial nations, growth stunting … is associated with worse indicators of adult well-being (e.g., income). … Here we … [consider] the Tsimane’, a foraging-farming society of native Amazonians in Bolivia. Subjects included 248 women and 255 men measured annually during five consecutive years (2002-2006). Nine outcomes (wealth, monetary income, illness, access to credit, mirth, schooling, math skills, plant knowledge, forest clearance) were regressed separately against a stunting dummy variable and a wide range of control variables. We found no significant association between any of the indicators of own well-being and adult stunting. …

In South Africa, a comparison of short-for-age “Cape Coloured” children showed that those growing up under poorer socioeconomic conditions had lower body weight, height, and physical performance than the more advantaged children … Among adults of industrial nations, standing physical stature is positively associated with many indicators of own adult well-being, such as occupation, monetary income, wages, IQ, longevity, and good health.

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  • http://wintershaven.net Jacob Wintersmith

    Strange. Even if the Tsimane live in an evolutionary equilibrium where the benefits of greater than average height are offset by its greater energy requirements, you would still expect to see effects in some of those outcomes.

  • stanfo

    This result helps clear our thinking.

    A theory of why height is positively correlated with IQ, income, etc…, should take into account why this is not true in a rural agrarian culture.

    My guess would be it has something to do with entrepreneurialism, as there is less room for that in the “foraging-farming society”.

  • http://williambswift.blogspot.com/ billswift

    Actually, this isn’t that surprising. There is no reason for size or strength to be strongly selected for in a hunter-gatherer culture; greater size and strength became an advantage only with the grueling labor of agricultural societies; in the respect of labor, farming-foraging societies are closer to hunter-gatherer economics than fully agricultural ones.

    • Michael Turner

      Actually, the amount of physical labor and size required for agriculture is roughly proportional to … the amount of physical labor and size required for agriculture! Most farming/foraging societies put their kids to work at a fairly young age, when they are still small, and kids might even be a win, in terms of the ratio of calories produced to those consumed. Their caloric requirements at that age are also small, even when they are working hard.

      So I would say there might be genetics at work here, but perhaps operating in almost the opposite way — a population that’s been subsisting on foraging/farming for a long time might have effectively bred itself to respond to famine better (in long-term cognitive performance terms) than long-term herding/hunting societies, where the typical reaction to food shortage might have been for the tribes of bigger people to kill off or starve out the smaller ones. Size might be of no intrinsic advantage or disadvantage in food-getting generally, but it certainly is an advantage in fighting.

      It might be interesting to compare with Japan. Kiichi Miyazawa was by far the most the most intelligent Prime Minister Japan has had in the last few decades, but he was also its shortest. I live in Japan, and kids these days are starting to get pretty tall, but without getting noticeably brighter. Looks like it’s kind of going the other way, if anything.

      • http://williambswift.blogspot.com/ billswift

        I don’t know about the tribe discussed here specifically, but the New Guinean farming-foraging cultures I read about 15 years ago, was more like suburban gardening in its physical requirements than historical agriculture as practiced in the Middle East and Medieval Europe, which was sheer backbreaking labor on the part of those actually practicing it. And only someone ignorant of agriculture would claim agriculture = agriculture; agriculture subsumes a huge variety of practices.

      • gwern

        > Most farming/foraging societies put their kids to work at a fairly young age, when they are still small, and kids might even be a win, in terms of the ratio of calories produced to those consumed. Their caloric requirements at that age are also small, even when they are working hard.

        I dunno; how would that work, exactly? I would expect kid labor to be less efficient than adult labor simply because kids need extra calories for growing, while adults aren’t growing.

    • http://robertwiblin.wordpress.com Robert Wiblin

      Regardless, wouldn’t size be a signal of genetic quality – if you can survive well despite the handicap of being huge, that shows just how fit you are otherwise!

  • jay

    I know it’s common sense that women most heavily have a bias against coupling with men who are short, much less shorter than themselves. This bias is evident across cultures. It’s as biologically ingrained as caring about whether or not your future husband has a job (reverse the sexes and think about the fact that men don’t care about these things, in general)

    In cultures where women have less opportunity for economic mobility, one factor in declining height of the population is perhaps that height becomes less important vs. ability to acquire resources once the economy contracts.

    These male birds have evolved do to crazy dances to attract mates since they have a lot of time on their hands living in an area where acquiring food is pretty easy.

    http://www.youtube.com/watch?v=P85LoHftEKs

    But… what if it wasn’t so easy. Priorities shift. Don’t get me wrong, I’m sure the issue is more complex than this because height is also affected by nutritional issues.

  • http://www.nancybuttons.com Nancy Lebovitz

    The Status Syndrome: maybe low status is debilitating in itself.