We are not well adapted to many things found in the modern diet. Some adaptation has occurred, and more eventually will.

Most of us do not handle excess sugar and startch well. These lead directly to heart disease and adult onset diabetes. They also promote cancer and are likely implicated in Alzheimer’s. Paradoxically, the body has several methods to get rid of excess sugar but it doesn’t use them. It seems we never adapted a means to deal with excess sugar and starch. They just get stored as fat. On the other hand, the body is quite adept at dealing with excess fat. It’s no problem. It will store some, and burn any excess.

Why aren’t we adapted to sugar? Ten thousand years may actually be enough to develop something. However, the agricultural revolution, though a shift from protein and fat to starch, was not a shift to excess starch. In fact, starvation was widespread worldwide until a hundred year ago. Only the top 2% got enough to eat. So there was no evolutionary advantage to throw away any source of energy. Thus as far as adaptation to excess sugar and starch goes, we are really just now starting out.

How could the body dump sugar?

There are a couple of mechanisms possible. The intestines absorb sugar through a glucose transporter, which is a gadget stuck in the cell wall that does just what the name implies. Cells can turn their transporters on and off. But they don’t.

Likewise, the kidneys dump toxins by indiscriminately dumping everything and then picking out what they want to retain; rather like cleaning off a desk by shoving everything into the trash and then picking through it for what should be saved. The kidneys could quite easily “decide” to let that sugar go. In fact, the SGLT2 Inhibitors work exactly that way.

Interestingly it seems that people may have had to adapt to any sugar at all in the first place. People that historically had virtually no access to starch and sugar, the arctic Inuit for instance, lacked the enzyme necessary to break down sucrose (table sugar) into glucose and fructose (sugar’s digestible forms).

What have we adapted to?

Besides possibly evolving the ability to consume sugar, we probably have adapted somewhat to excess starch and sugar. When modern non-arctic hunter-gatherers (there are still 200 tribes) stop eating their traditional diet and start eating ours, they typically have a lot higher incidence of adult onset diabetes. This could be due to poor diet, or we, the Royal ‘we’ of everyone else, might be better adapted to such nutrients as potato chips and soda pop. ‘Better’ not great.

Babies can drink milk. In hunter-gatherers societies  and in many other cultures, this stops at an early age.  In Western cultures, we typically switch to cow milk. This seems to cause little problem. However, cultures that didn’t have this practice have a tough time. Apparently there is a gene induction that keeps the milk digestion capability going if so challenged. Most westerners have it, most Chinese do not simply due to dietary behavior. The adaptation to keep the milk flowing, as it were, is interesting. It seems to have happened in different ways in different places. Culture contributes to biology.

Disease Adaptation

Infectious disease isn’t unknown in the hunter-gatherer world, but it isn’t rampant either. However, until 100 years ago, it was the primary cause of death in our world. This was due to multiple factors: unsanitary conditions, cohabiting with animals, crowding and so on. While specific disease immunity isn’t passed on – possibly not true but this still reflects current conventional wisdom –  any genetic resistance would not only pass on, it would be strongly selected. Smallpox is a perfect example. Before vaccination, the mortality rate in Europe was around 30%. This is certainly high, but when these Europeans arrived in the New World, the natives there experienced a mortality rate often exceeding 95%. The lack of disease resistance was by far the major cause of the demise of the North and South American aboriginal populations.

Alcohol and alcoholism

When a previously “dry” culture gets access to alcohol all hell tends to break loose. Alcoholism tends to be high, along with its myriad problems. However cultures that have had access to alcohol for a long time tend to have relatively low rates of alcoholism. Genetic selection likely is at work here too.

A very curious adaptation

It seems that our ancestors from10,000 years ago had slightly larger brains than we do to day. This could be an adaptation. For most of the agricultural revolution, hard and menial labor was the lot of most, day after day, century after century. A brain might be of little use, and the brain is a major energy guzzler.

A hunter-gatherer, though, lives by continually out witting his prey. We certainly didn’t become the top predator by brawn.

Brains count now. Perhaps we are again evolving larger ones. But sometimes we wonder.