Wednesday, June 12, 2013

Starch Tolerance: From Ancient Genes?

Anthropology professor Brian Fagan on diets of human ancestors:

The Neanderthals were expert hunters, but when did hunting begin? Once again, the answer lies in Africa. Homo ergaster [a human ancestor from two million years ago] was an omnivore, completely accustomed to quite drastic environmental changes in the distribution of open grassland, forest, and semiarid terrain and the dietary shifts that went with them. Unlike their predecessors, these people were serious hunters and meat eaters--because they dwelled for the most part in open country, where meat was the dominant, though not, of course, only food source. We know this because the bones of numerous large mammals appear alongside stone butchering tools in some of the archeological sites that document their wanderings, whereas none appear in sites that predate them.
Brain size is largest among species that hunt large mammals opportunistically while cooperating with and depending on one another. Brain size also correlates with time spent as a juvenile, which in turn relates to exploration, learning and play. Complex social organization such as that possessed by Homo ergaster required intelligence gathering, analysis of that information, and creative uses of it.

These hunting skills, and the weaponry that went with them, developed in Africa after two million years ago and survived virtually unchanged among premoderns everywhere for almost all of that time, until the late Ice Age, some fifty-five thousand years ago.(1)

Yet why do some people tolerate high-carb diets so well? My thinking is that over two million years, some humans lost their ability to thrive on a high-carb diet, while others retained it from their very ancient ancestors, who were largely herbivores. (Or people severely intolerant of high-carb diets were winnowed out through natural selection. Or both.) Diabetes, for instance, has a genetic component; you won't get it without the genes. There's a wide variation in how many copies of the salivary amylase gene people carry. (The article mentions "intense positive selection" in populations eating a starchy diet.) (2) Dr. William Davis notes that people who carry the gene for lipoprotein (a) tend to be "the perfect carnivore": intelligent, athletic, tolerant to dehydration, tolerant to starvation, and resistant to tropical infections. But they're prone to heart disease and diabetes--even the marathoners. Davis says carbohydrate consumption and vegetable oils worsen their tendencies toward heart disease and diabetes.(3) Native Americans and First Peoples of Canada, some of whom have had only a few hundred years to adapt to a high-carb diet, have some of the highest rates of diabetes in the world. Even going to an agricultural diet of "real food," not flour and sugar, created problems for some of them, including more infections, iron deficiency anemia, infant mortality and cavities.(4) 

Our ancestors' diet shifted greatly two to three million years ago from plant-based to meat being a substantial part of the diet, as Richard Leakey put it. We definitely adapted to meat eating--our teeth and short digestive tract show this. But we all know people who can eat quite a bit of starch and stay healthy and trim. Perhaps they retained some very ancient genes, while others are children of Homo ergaster.  

1. Cro-Magnon: How the Ice Age Gave Birth to the First Modern Humans by Brian Fagan. 2010, Bloomsbury Press, New York. pp. 24-26.
2. "Copy number polymorphism of the salivary amylase gene: implications in human nutrition research." by
Santos JL, Saus E, Smalley SV, Cataldo LR, Alberti G, Parada J, Gratacòs M, Estivill X. J. Nutrigenet Nutrigenomics, September 3, 2012.
3. "The Perfect Carnivore." Track your Plaque blog by Dr. William Davis. October 2, 2012.
4. "Nutrition and Health in Agriculturalists and Hunter-Gatherers" by Dr. Michael Eades. Protein Power blog, April 22, 2009.


tess said...

That makes a lot of sense to me - looks like I'm one of those modern mutants.... ;-)

Lori Miller said...

Hey, that's a good thing to tell vegetarians who say that we evolved as herbivores. Yeah, we did, if you go back three or four million years to when we were more chimp-like than human.