BBC, NYTimes: We’re evolving. Just check our spit. It handles starch.
In Nature Genetics a 13-person team of US anthropologists, genticists, nutritionists etc. report that an evolutionary tale is told in our salivary glands. Specifically, by comparing how many genes for the starch-digesting enzyme amylase exist in people v. other primates and, more intriguing, between different human populations. Peoples that eat plenty of starch, which means most of us, have many more copies of the gene than do isolated and traditional populations, such as sub-Arctic and African hunter-herders who consume mainly meat or blood.
The gene is expressed into saliva, meaning that starch to a significant degree can be converted to sugar and absorbed in the mouth.
The lead authors are at UC Santa Cruz and Arizona State U. One surmise they offer is that the change to favor the gene in early humans permitted a shift from fruit and meat diets to include starchy tubers and grains, a major new source of nourishment for evolving bigger, energy-hungry brains. Human teeth, the paper says, are more fit for chewing up tough, starchy food than for eating meat — another candidate as the source of extra energy needed to have large brains. The pre-digestion of starch, it also says, helps evade nutritional hazards of diarrhea.
In the NYTimes, Nicholas Wade starts off with a puckish musing whether we can evolve, eventually, to stuff ourselves and stay skinny. He gets a bit into the details, too, including that it’s not clear whether low-amylase people today are descended from groups that never had much of it, or that lost some copies as they drifted into lifestyles or terrains with scant starch.
-CP
Other stories:
BBC runs it with a pic of potatoes and notes that average Brit eats more than a spud per day; Nature.com Ewen Callaway;
Grist for the Mill: UC Santa Cruz Press Release;
Further press agentry note: The UCSC release, lightly rewritten by ScienceDaily, gets run verbatim at several specialty sites, such as DentalPlans.com;
Pic: From UCSC – big Tanzanian tubers cooking.
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