john hawks weblog

paleoanthropology, genetics and evolution

nutrition

  • Mailbag: Thick skulls and diet

    Tue, 2011-04-12 23:15 -- John Hawks

    Re: "Hard headed science":

    Although genetics undoubtedly play a part in the thickness of the skull bone, there is another parameter that more often than not is overlooked by anthropologists. That parameter is nutrition. Modern man is overfed on calories but malnourished on micronutrients. Soft tissues always evolve to their fullest, but the hard tissues, i.e. bone, are much more dependent on nutrition and physical work-load. Compared to the skulls of its ancestors, the skull of modern man is thinner, smaller, narrower, the eye sockets tend to be rounder and there tends to be insufficient space for the teeth in the mouth. It seems reasonable to me that in so far as the shape of the skull, it is the phenotype that’s changed, not the genotype.

    Nutrition can make a difference, but the variation in skull thickness during the last 2 centuries is very minor compared to the amount of difference between Homo erectus, Neandertals and us. The thinning also preceded any significant shift from hunting and gathering to agriculture. There has been further thinning after agriculture, so that we can't attribute the shift to a straightforward diet change.

    Tags: 
    Homo erectus
    paleopathology
    nutrition
    diet

  • Lasting supper

    Sat, 2010-09-11 10:09 -- John Hawks

    This is a great story about "portion sizes" increasing over the centuries in "Last Supper" paintings, but I haven't been able to get the paper yet.

    The Cornell University team studied 52 of the most famous paintings of the Biblical scene over the millennium and scrutinised the size of the feast.

    They found the main courses, bread and plates put before Jesus and his disciples have progressively grown by up to two-thirds.

    This, they say, is art imitating life.

    I wonder, though, how much of the "bread size grew by 23%" and "plate size increased by 66%" might be technological rather than merely food preference-caused. They introduced different plate production and bread production methods over time (not sure if all the breads are unleavened, either).

    Tags: 
    diet
    art
    nutrition
    art in science

  • Mailbag: Milk drinking

    Fri, 2010-07-02 09:53 -- John Hawks

    I read some older posts on your blog about dispersal of lactase persistance world wide. Is it not so that everyone can digest lactose at birth and that the production of the enzyme lactase persists as long as milk consumption persists, whether it is human, goat or cows milk? There is also the matter of pasteurization which kills beneficial bacteria that help digest the lactose. Raw milk is better tolerated than pasteurized milk by all populations wordwide, and as far as I can tell; lactose intolerance is actually an intolerance to pasteurized milk.

    Even those who drink pasteurized milk have plenty of beneficial bacteria, but bacterial digestion of lactase in the gut is problematic. The bacteria generate lactic acid and CO2, which in large quantities lead to malabsorption of other nutrients and discomfort.

    Malabsorption apparently was not a barrier to early dairying peoples; today pastoralists who rely on milk but do not have lactase persistence tend to ferment or culture the milk in ways that cut lactose content.

    The target of selection on lactase persistence was likely energy recovery. Lactose accounts for roughly 30 percent of the calories in milk, and increasing the fraction absorbed was probably highly beneficial, particularly for pregnant and lactating women. But some scientists think that the target of selection was the intestinal effect of lactose-absorbing bacteria, as diarrheal diseases exerted a high mortality risk in preindustrial peoples.

    Small amounts of milk will not hurt anyone unless they have a milk allergy, which is a separate issue. Lactase production is universal in infants, children's lactase production declines at an age that varies but is usually late childhood or adolescence.

    Tags: 
    nutrition
    recent selection
    diet

  • Papyrus and A. boisei

    Fri, 2010-06-11 17:20 -- John Hawks

    I've had on my stack for quite a long time, a short paper by Nicholas van der Merwe and colleagues, assessing the stable carbon isotope ratios in several specimens from Tanzania. These include the Homo habilis specimens OH7, OH62 and OH65, and the A. boisei specimens OH5 and the Peninj mandible.

    The ratio of stable carbon-13 and carbon-12 enable an assessment of the amount of C4 versus C3 plants in the diet. I discussed the basic ideas in a longer post from 2005.

    The results on the Homo specimens are not too surprising. All three specimens overlap with South African A. africanus. OH7 and OH62 in particular have values around 20% C4, which is right near the mean observed for South African Homo and A. robustus from Swartkrans. OH65 has a higher C4 percentage than the other two, but within the range observed for Sterkfontein Member 4 A. africanus, which was significantly higher than Makapansgat or the other South African samples. So it would appear that the diet of Homo habilis did not differ from earlier hominins in terms of the ultimate origin of carbon in grasses versus non-grass plants.

    What is more surprising is the extremely high amount of C4-derived carbon in OH5 and Peninj. They score 77% and 81% C4, respectively. These are the only two specimens of A. boisei for which these stable isotopes are known, and they are very far from the observed range in the South African A. robustus.

    The authors suggest an interesting source for this high C4 proportion -- papyrus. They described a tasting tour of the wild plants of the Okavango:

    Bamford and van der Merwe investigated (and ate) the edible plants of the Okavango Delta in Botswana during the dry season (July 2003), assisted by Ezaya Karesaza, a tourist guide who grew up in this extensive wetland. Among the C3 plants that are traditionally eaten raw in this region are a variety of fruits and seeds, as well as plants of which the leaves and rhizomes are eaten. The latter include Aeschynomene fluitans, a floating legumi- nous plant, of which the leaves taste like lettuce; Typha capensis, which grows in thick stands along the water’s edge, of which the rhizomes have a pleasant taste; and Schoenoplectus corymbosus, a big water sedge, of which the stem is succulent at the bottom end. Among C4 plants, the rhizomes and culms of three other species of sedges are edible. These include Cyperus denudatus and C. dives, which grow in the grasslands of the floodplains. Unlike the grasses, they are green year-round, although not particularly prolific. The most common C4 sedge, by far, is Cyperus papyrus, which grows in dense thickets along the water edge. This species has culms as high as 4 m, of which the lowermost 0.5 m is frequently chewed by local people. It has a soft, white rind about 0.5 cm thick; the interior, about 2 to 3 cm in diameter, is more fibrous. It is chewy and pleasant tasting. The thick rhizome of papyrus is more fibrous and starchy than the culm, somewhat astringent, and requires considerable chewing effort. It produces a bolus in the mouth that has to be spat out at intervals.

    They then reported the results of a nutritional analysis of the papyrus culm and rhizome, which have roughly the nutritional and caloric value of domestic potatos, although would require a significant gut flora to deal with the cellulosic content.

    All in all, it's very curious that A. boisei is so different in these isotopic values compared to other early hominins. The theme was picked up last year in a paper by Richard Wrangham and colleagues, who focused on the idea of "fallback foods" -- the kinds of foods that an animal does not prefer, but eats when other more highly preferred foods are not available. Considering the very high C4 proportion indicated by the OH5 and Natron isotope values, it doesn't seem likely that this reflects a fallback strategy, but possibly an initial exploitation of such resources as fallbacks facilitated a later, more developed adaptation to them.

    Related posts:

    "Chemistry and early hominid diets"

    "Robust australopithecine diet ablated"

    "Average diet versus extreme diet in robust australopithecines"

    References:

    van der Merwe NJ, Masao FT, Bamford MK. 2008. Isotopic evidence for contrasting diets of early hominins Homo habilis and Australopithecus boisei of Tanzania. S Afr J Sci 104:153-155.

    Wrangham R, Cheney D, Seyfarth R, Sarmiento E. 2009. Shallow-water habitats as sources of fallback foods for hominins. Am J Phys Anthropol 140:630-642. doi:10.1002/ajpa.21122

    Tags: 
    A. boisei
    diet
    Olduvai Gorge
    Australopithecus
    nutrition
    Tanzania

  • UC-Berkeley genetic tests for freshmen

    Wed, 2010-05-19 15:15 -- John Hawks

    I'm not sure which tags to apply to this story. I'm torn between "colossally-bad-ideas" and "university-auditions-for-big-brother".

    Berkeley asks freshmen for DNA samples

    Instead of the usual required summer-reading book, this year’s incoming freshmen at the University of California, Berkeley, will get something quite different: a cotton swab on which they can, if they choose, send in a DNA sample.

    This is so unbelievable that I looked all over the web for news stories to confirm it isn't just a late April Fools. What conceivable educational value do they think is going to come out of this?

    The university said it would analyze the samples, from inside students’ cheeks, for three genes that help regulate the ability to metabolize alcohol, lactose and folates.

    Those genes were chosen not because they indicate serious health risks but because students with certain genetic markers may be able to lead healthier lives by drinking less, avoiding dairy products or eating more leafy green vegetables.

    WTF?!

    Hey, Berkeley! Great plan! I'm sure that your lactose intolerant students will shocked to discover that they're lactose intolerant! OMG! That explains the milkshakes! Likewise, I'm sure that the health impacts of alcohol consumption will get your 18-year-old freshmen to booze less on the weekends! And that folate metabolism test, well, that will get them used to supplements, won't it?

    I mean, seriously. Nutrigenomics is a legitimate field of investigation, but testing individuals for genes that relate to nutritional requirements has become the smelly armpit of "personalized genomics". Companies selling "personalized diet plans" or "nutritional supplements" based on supposed genetic testing have become a problem and subject of recurrent FTC investigations. There is no credible science that supports such supplements or plans, outside known nutritional deficiencies.

    In fact, there is no credible science that supports the idea that knowing your lactase persistence genotype, alcohol metabolic genotypes, or "folate" metabolic genotypes will improve health.

    This information is useless. It's a total waste of money. It gives a highly misleading picture of genetics.

    The most probable outcome is to condition 18-year-olds to accept government-sponsored genotyping. So to make it complete, the program comes with a lack of adequate privacy safeguards. The proposal has students using "bar codes" to access their data on a public website.

    Yeah, great! That's about as "anonymous" as your drink order at a coffee shop.

    Tags: 
    politics
    biotech
    education
    nutrition
    testing
    diet
    genomics

  • Food guidelines

    Fri, 2010-01-15 07:30 -- John Hawks

    As long as I'm linking to the Daily Mail for their "Neanderthal metrosexuals" quip, I thought I'd pass along a story I liked -- "Unlikely but brilliantly simple rules to transform the way we eat" from dilemmistic omnivore Michael Pollan.

    The whiter the bread, the sooner you'll be dead

    There are maybe twenty of these little guidelines, mostly clever but not generally rhyming. My favorite:

    It's not food if it has the same name in all languages.

    Explanation: "Think Big Mac or Pringles."

    Tags: 
    health
    diet
    nutrition

  • You are what your ancestors ate, part 1

    Fri, 2009-12-11 13:20 -- John Hawks

    Ann Gibbons has a long news article in the current Science reporting on an interdisciplinary conference on recent human diet evolution ("What's for Dinner? Researchers Seek Our Ancestors' Answers"). The article covers a lot of ground, from Michael Richards' work on the isotopic signature of diet in early Upper Paleolithic people, to Bill Leonard's work on diet adaptations in Siberian reindeer herders, to Jonathan Wells' work on maternal nutritional status and epigenetics.

    It's a good "why evolution matters to today's nutritional choices" article.

    A section of interest to me:

    The agricultural revolution favored people lucky enough to have gene variants that helped them digest milk, alcohol, and starch. Those mutations therefore spread among farmers. But other populations remained more carnivorous, such as the Saami of frigid northern Norway, whose ancestors herded reindeer. Among Saami ancestors, genes to digest meat and fat efficiently were apparently favored. One gene variant, for example, makes living Saami less likely to get uric acid kidney stones—common in people who eat high-protein diets—than are people whose ancestors were vegetarian Hindus and lack this gene variant, says geneticist Mark Thomas of University College London (UCL).

    I'll have more on a similar topic later -- recent shifts in genes due to agricultural subsistence has become a favorite subject of local interest. One would think I might get some funding from the Wisconsin dairy industry for this, but nothing so far...

    There is an unresolved tension in the article: Is there a better diet for everyone? Clearly some populations have undergone large recent diet changes with bad consequences; the same bad outcomes occur in some people despite possibly adapting to new diets for thousands of years. And yet, every metabolic or diet-related syndrome is variable, and we know that some genes related to digestion and metabolism have rapidly changed. "Westernization" is not as simple as it seems, nor is agriculture (or, for that matter, pastoralism) -- and the responses to each vary for stochastic reasons in different populations.

    It's a good interesting complexity, in a field where simple categorical statements can get a lot of attention.

    Tags: 
    nutrition
    recent selection
    diet
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Neandertals

For years, I've worked on their bones. Now I'm working on their genes. Read more about the science studying these ancient people.

Denisova

From a finger bone of an ancient human came the record of a completely unexpected population. My lab is working on the science of the Denisova genome.

Acceleration

The advent of agriculture caused natural selection to speed up greatly in humans. We're uncovering some of the ways that populations have rapidly changed during the last 10,000 years.

Malapa

Just outside Johannesburg, the Malapa site is producing some of the most exciting finds in human evolution. This site is the headquarters of the Malapa Soft Tissue Project.