You Are What They Ate

Fad diets abound in our society, sometimes they are backed by folklore, bad-science, pseudo-science, your mother or just wishful eat-thinking. Ugly hard-cover diet books pepper the sale shelves at bookstores. Everybody seems to have an answer, and nobody is persistently right.

But, diet is serious scientific business especially in the context of human evolution and adaptation. Can we reconcile our understanding of dietary adaptations over deep time with what you should make for dinner tonight? Well, perhaps with caution and a little nostalgia, it’s possible.

One hallmark of our genus, Homo, is a brain larger than that of our hominin forebearers. An explanation posited for the evolutionary burgeoning of the hominin brain is a dietary shift. The idea is that our brain, energetically, is an expensive tissue to develop and maintain and more dense high-calorie foods would have been required to support its needs. Maybe it was meat, they say. It has also been suggested that tubers may have provided crucial calories to hominins in times where other foods may have been scarce.

The above hypotheses have been tested in extant taxa and are continually being explored via environmental reconstruction, hunter/gatherer analogy and extensive mechanistic and isotopic studies of dentition. Fast forward to a more modern time, the onset of agriculture and animal domestication, approximately 10,000 years ago. Genetic adaptations to digest lactose and starch have been discovered in living human populations and temporally traced to major shifts in cultural food practices. Also, some populations have better tolerance for metabolizing alcohol. A recent paper just came out that Japanese people borrow bacteria from sushi, it then integrates into their stomach flora and enables better digestion of sushi. And there may be some evidence that this borrowed marine bacteria is heritable from parent to child!

The foods are diverse, but idea is the same. If we assert that diet is an environmental element that has driven selection and adaptation, then what we are saying is that certain individuals have some genetic or metabolic mechanism that allows them to better handle the foods that are in abundance. They are then healthier, have more offspring, the trait is honed and handed down to future generations. Its the classic gene-culture interaction.

This brings me to my main point. I think that the foods that we are best equipped to digest and glean the most nutrients from are foods that our very recent ancestors ate. I think there must be some more nuanced, as yet undiscovered, physiological adaptations to what people were eating just a few generations ago in your lineage.

So, eat mainly what your grandmother made, or what her grandmother did, but dont necessarily eat what mine did. Its a reason to hand recipes down with mitochondria. Oh and maybe its all just an excuse for me to go to Motorino’s and to drink Chianti, you say? well so what if it is.