(Please read Part I, Part II, and Part III first.)
7. Insulin and Low-Carbohydrate Diets
The revival of Brand's doctrine of CoEvolution in recent years was sparked by increasing popularity of low-carbohydrate diets (Atkins etc.) These diets have a principled, scientific basis derived from the study of the role of insulin in the human body.
Insulin is secreted into the blood stream in response to high levels of glucose in the blood. Insulin promotes the conversion of excess glucose into triglycerides, and eventually body fat: this is how energy is stored in times of abundance for use in times of famine.
The first function of insulin is to protect the body from excess levels of glucose. Diabetes, a group of diseases marked by the lack of normal release of insulin in response to an excess of glucose, leaves the body exposed to severe damage from excess glucose.
The second function of insulin is to convert the overly abundant glucose into triglycerides, and eventually into body fat for energy storage. The absence of insulin causes the reverse: conversion of stored fat to usable energy.
The third is to increase hunger. Until the last half-century, most human populations were plagued by famines, often exacerbated by tyranny and war. A human who had stored enough fat in times of plenty could survive a famine more often; insulin hunger encouraged more eating, and the formation of more stored fat, in those rare times when there was more than enough to eat. More fat also meant more cardiovascular disease and a shorter lifespan, but in most cultures, what happened to the individual after the age of reproduction and child-rearing had little evolutionary impact. In most local environments human evolution favored fat for surviving a famine, and a lifespan of 30-40 years.
In recent decades modern agricultural technology changed this picture. With the threat of famine removed, first in the West and then elsewhere, humans started to aim for a longer individual lifespan. In the context of changed goals, such as achieving lifespans of eight decades or longer, fat became an obstacle instead of an advantage. The logical solution, in view of the scientific identification of the three roles of insulin, was to fight fat and its consequences by limiting the intake of carbohydrates, and thus limiting blood glucose levels to below the threshold for the release of insulin. Hence the advice, from Atkins 1972 onward, to limit one's intake of bulk carbohydrates to less than one gram per two kilograms of body weight per day.
This advice was not unopposed. Before the three roles of insulin had been identified, diets were based on a well-understood principle: the law of conservation of energy. Every calorie of energy eaten must be either excreted, expended, or stored. To store less energy in the form of body fat, one must eat fewer calories. The advice to stop counting calories, even if only to count grams of carbohydrates instead, seemed unprincipled. The advocates of low-carb diets were telling patients to stop acting on principle and to act on a gimmick instead. The trouble was that for many, albeit not for everyone, the gimmick worked.
Of course the low-carb diets did not repeal the law of conservation of energy. They worked because, in the absence of insulin, the low-carb dieter was not hungry and ate fewer calories. (The Atkins diet also encouraged the consumption of high-fiber greens, facilitating the elimination of excess food from the digestive tract.) In contrast, the traditional calorie-counting dieter often consumed most of her closely watched calories in the form of bulk carbohydrates - and her insulin spiked, causing hunger. And so the calorie-counter was discouraged, stressed, tempted to cheat. The difference was, and is, a fascinating illustration of the importance of tracking the context when one is following a principle.
8. CoEvolution Becomes "Paleo."
Stewart Brand renounced the doctrine of CoEvolution when phyletic gradualism, on which the doctrine was based, had been disconfirmed and replaced by punctuated equilibrium. But, just like dietitians attached to the principle of calories, the now disconfirmed principle of CoEvolution had adherents who evaded, ignored, or simply did not understand the principle of punctuated equilibrium.
One anthropological observation sometimes cited in favor of low-carbohydrate diets was that pre-European-contact Eskimos lived on what was practically the highest-fat, lowest-carbohydrate diet on the planet, yet were physically fit enough to thrive in the world's most adverse environment. To the remaining believers in CoEvolution this made sense: the Eskimos lived without agriculture or industry, much as Paleolithic men had lived ten thousand years ago. Similarly, pre-agricultural tribes inhabiting tropical islands where there had never been famines, did not exhibit the cardiovascular pathologies observed in environments where fat accumulation had evolved as an adaptation to periodic famine. In the context of punctuated equilibrium, these would be viewed as examples of rapid (and possibly recent) evolutionary adaptation to local conditions. Believers in CoEvolution, however, saw in those selected anthropological observations a validation of their belief that a return to a Paleolithic lifestyle was a recipe for the achievement of optimal health - optimal health that humans had been designed for by slow (Co)Evolution over hundreds of thousands of years. Thus was CoEvolution re-born as "Modern Paleo." Unlike punctuated equilibrium, it was a principle that one did not need measure theory to understand. Thus one could do a low-carbohydrate diet not as a "gimmick" using the peculiar relation of hunger to insulin, but as part of the application of "The Principle of Evolution." It was no longer the principle of how evolution was understood to work, by those who cared to understand how it worked. But it did correspond to how evolution had been formerly thought to work, and how it was still thought to work by nearly everyone else. And for the popular self-help culture that was good enough.
Unfortunately for adherents, the Modern Paleo Principle leads to something quite different from optimal health - unless modified by altogether non-paleolithic, industrial-strength food supplements. The most telling example is iodine. No one really knows why, but a low-carbohydrate diet, when it does not include plenty of seafood and kelp, sometimes causes an iodine deficiency severe enough to end in hypothyroidism. And so "Modern Paleo" adherents are the world's best consumers of un-paleolithic, industrially purified, high-potency Iodine/Potassium Iodide tablets.
It happens that all "contemporary Paleo" cultures that have been found by anthropologists to enjoy relatively good health, live on islands or on seashores, where they get plenty of iodine in their diet from seafood and from kelp and other marine vegetation. Somehow even the most non-Paleolithic islanders, such as the modern Japanese, are also very healthy, as long as they get enough iodine from seafood and kelp. Even if, as in the case of the Japanese, the bulk of their diet is rice and other modern grains.
One explanation of the iodine link is that iodine is needed to live without bulk carbohydrates. So how did inland primitives live and reproduce without industrial iodine? It turns out that they ate bulk carbohydrates. Wild sugar cane is a favorite of inland primitives in New Guinea. Wild rice (Zizania) was a staple in the diet of pre-Columbian inland North Americans. Low-carb might not be, for at least some of us, a return to the diet of our stone-age ancestors.
Another potential explanation is that some of us may have had more recent ancestors who lived on islands or by the shore. The very rapid evolution to local optima - an aspect of punctuated equilibrium - would have moved the relevant ancestral genomes in the direction of dependence on abundant iodine in the diet. Some people today may need industrial iodine supplements, because some of their specific ancestors had evolved to depend on high levels of this specific nutrient.
Evolution does not do design. We are not "designed by evolution" to eat the food or live the lives of our Paleolithic ancestors. What evolution is known to have done, is to quickly if imperfectly adapt one's specific ancestors, who lived in hundreds of different environments, to be fit to survive and reproduce in those specific environments - and not in the ancestral environments of other humans. The daily food of one may be pain or death to another. The real universal principle is to use one's mind to create for oneself, by systematic self-knowledge and by the artifice of one's mind, a diet and an environment that will compensate for evolution's lack of design.