61
" If farming was “the biggest mistake in human history,” which triggered lots of evolutionary mismatch diseases, then why did it spread so rapidly and thoroughly? The biggest reason is that farmers pump out babies much faster than hunter-gatherers. In today’s economy, a higher reproductive rate often entails ominous connotations of expense: more mouths to feed, more college tuition bills to pay. Too many children can be a source of poverty. But to farmers, more offspring yield more wealth because children are a useful, fantastic labor force. After a few years of care, a farmer’s children can work in the fields and in the home, helping to take care of crops, herd animals, mind younger children, and process food. In fact, a large part of the success of farming is that farmers breed their own labor force more effectively than hunter-gatherers, which pumps energy back into the system, driving up fertility rates.20 Farming therefore leads to exponential population growth, causing farming to spread. Another factor that encouraged the spread of agriculture is the way farmers alter the ecology around their farms in ways that hinder if not prevent any more hunting and gathering. Occasionally "
― Daniel E. Lieberman , The Story of the Human Body: Evolution, Health, and Disease
65
" To be sure, the early days of the Industrial Revolution were rough going, but within a few generations, innovations in technology, medicine, government, and public health led to effective solutions for many of the mismatch diseases caused by the Agricultural Revolution, especially the burden of infectious disease from living at higher population densities with animals and in unsanitary conditions. Not all of these advances, however, are available to people unfortunate enough to live in poverty, especially in less developed nations. In addition, the progress made over the last 150 years has also come with some consequential drawbacks for people’s health. Most essentially, there has been an epidemiological transition. As fewer people succumb to diseases from malnutrition and infections, especially when they are young, more people are developing other kinds of noncommunicable diseases as they age. This transition is still ongoing: in the forty years between 1970 and 2010, the percentage of deaths worldwide from infectious disease and malnutrition fell by 17 percent and life expectancy increased by eleven years, while the percentage of deaths from noncommunicable diseases rose by 30 percent.61 As more people live longer, more of them are suffering from disability. In technical terms, lower rates of mortality have been accompanied by higher rates of morbidity (defined as a state of ill health from any form of disease). "
― Daniel E. Lieberman , The Story of the Human Body: Evolution, Health, and Disease
67
" Another set of mismatch diseases that can be caused by farming diets are nutrient deficiencies. Many of the molecules that make grains like rice and wheat nutritious, healthful, and sustaining are the oils, vitamins, and minerals present in the outer bran and germ layers that surround the mostly starchy central part of the seed. Unfortunately, these nutrient-rich parts of the plant also spoil rapidly. Since farmers must store staple foods for months or years, they eventually figured out how to refine cereals by removing the outer layers, transforming rice or wheat from “brown” into “white.” These technologies were not available to the earliest farmers, but once refining became common the process removed a large percentage of the plant’s nutritional value. For instance, a cup of brown and white rice have nearly the same caloric content, but the brown rice has three to six times as much B vitamins, plus other minerals and nutrients such as vitamin E, magnesium, potassium, and phosphorus. Refined "
― Daniel E. Lieberman , The Story of the Human Body: Evolution, Health, and Disease
68
" One way to quantify the extension of morbidity currently occurring is a metric known as disability-adjusted life years (DALYs), which measures a disease’s overall burden as the number of years lost to ill health plus death.65 According to an impressive recent analysis of medical data worldwide from between 1990 and 2010, the burden of disability caused by communicable and nutrition-related diseases has plunged by more than 40 percent, while the burden of disability caused by noncommunicable diseases has risen, especially in developed nations. As examples, DALYs have risen by 30 percent for type 2 diabetes, by 17 percent for neurological disorders, such as Alzheimer’s, by 17 percent for chronic kidney disease, by 12 percent for musculoskeletal disorders, such as arthritis and back pain, by 5 percent for breast cancer, and by 12 percent for liver cancer.66 Even after factoring in population growth, more people are experiencing more chronic disability that results from noncommunicable diseases. For the diseases just mentioned, the number of years a person can expect to live with cancer has increased by 36 percent, with heart and circulatory diseases by 18 percent, with neurological diseases by 12 percent, with diabetes by 13 percent, and with musculoskeletal diseases by 11 percent.67 To many, old age is now equated with various disabilities (and "
― Daniel E. Lieberman , The Story of the Human Body: Evolution, Health, and Disease
69
" Another risk of long-term food storage is contamination. Aflatoxins, for example, are harmful compounds produced by funguses that thrive on cereals, nuts, and oilseeds and that can cause liver damage, cancer, and neurological problems.32 Since hunter-gatherers don’t store foods for more than a day or two, they rarely if ever encounter these toxins. An additional and very significant health problem caused by farmers’ diets is due to lots of starch. Hunter-gatherers "
― Daniel E. Lieberman , The Story of the Human Body: Evolution, Health, and Disease
70
" Further, although it makes sense for doctors and public health officials to categorize diseases based on whether they are caused by infections, malnutrition, tumors, and so on, an evolutionary perspective suggests that we should also look at the extent to which diseases are caused by evolutionary mismatches between the environmental conditions (including diet, physical activity, sleep, and other factors) for which we evolved and the environmental conditions that we now experience. "
― Daniel E. Lieberman , The Story of the Human Body: Evolution, Health, and Disease
71
" How did farming change how much physical activity we do and how we use our bodies to do the work? Although hunting and gathering is not easy, nonfarming populations like the Bushmen or the Hadza generally work only five to six hours a day.36 Contrast this with a typical subsistence farmer’s life. For any given crop, a farmer has to clear a field (perhaps by burning vegetation, clearing brush, removing rocks), prepare the soil by digging or plowing and perhaps fertilizing, sow the seeds, and then weed and protect the growing plants from animals such as birds and rodents. If all goes well and nature provides enough rain, then comes harvesting, threshing, winnowing, drying, and finally storing the seeds. As if that were not enough, farmers also have to tend animals, process and cook large batches of foods (for example by curing meat and making cheese), make clothing, build and repair homes and barns, and defend their land and stored harvests. Farming involves endless physical toil, sometimes from dawn to dusk. As "
― Daniel E. Lieberman , The Story of the Human Body: Evolution, Health, and Disease
72
" One very simple way to compare the workloads of farmers, hunter-gatherers, and modern postindustrial people is to measure physical activity levels (PALs). A PAL score measures the number of calories spent per day (total energy expenditure) divided by the minimum number of calories necessary for the body to function (the basal metabolic rate, BMR). In practical terms, a PAL is the ratio of how much energy one spends relative to how much one would need to sleep all day at a comfortable temperature of about 25 degrees Celsius (78 degrees Fahrenheit). Your PAL is probably about 1.6 if you are a sedentary office worker, but it could be as a low as 1.2 if you spent the day in a hospital on bed rest, and it could be 2.5 or higher if you were training for a marathon or the Tour de France. Various studies have found that PAL scores for subsistence farmers from Africa, Asia, and South America average 2.1 for males and 1.9 for females (range: 1.6 to 2.4), which is just slightly higher than PAL scores for most hunter-gatherers, which average 1.9 for males and 1.8 for females (range: 1.6 to 2.2).38 These averages don’t reflect the considerable variation—daily, seasonal, and annual—within and between groups, but they underscore that most subsistence farmers work as hard if not a little harder than hunter-gatherers and that both ways of life require what people today would consider a moderate workload. "
― Daniel E. Lieberman , The Story of the Human Body: Evolution, Health, and Disease
73
" Hunter-gatherers who survive childhood typically live to be old: their most common age of death is between sixty-eight and seventy-two, and most become grandparents or even great-grandparents.70 They most likely die from gastrointestinal or respiratory infections, diseases such as malaria or tuberculosis, or from violence and accidents.71 Health surveys also indicate that most of the noninfectious diseases that kill or disable older people in developed nations are rare or unknown among middle-aged and elderly hunter-gatherers.72 These admittedly limited studies have found that hunter-gatherers rarely if ever get type 2 diabetes, coronary heart disease, hypertension, osteoporosis, breast cancer, asthma, and liver disease. They also don’t appear to suffer much from gout, myopia, cavities, hearing loss, collapsed arches, and other common ailments. To be sure, hunter-gatherers don’t live in perpetually perfect health, especially since tobacco and alcohol have become increasingly available to them, but the evidence suggests that they are healthy compared to many older Americans today despite never having received any medical care. In short, if you were to compare contemporary health data from people around the world with equivalent data from hunter-gatherers, you would not conclude that rising rates of common mismatch diseases such as heart disease and type 2 diabetes are straightforward, inevitable by-products of economic progress and increased longevity. Moreover, "
― Daniel E. Lieberman , The Story of the Human Body: Evolution, Health, and Disease
74
" the biggest workload difference between these economic systems is not in terms of adult labor, but child labor. According to the anthropologist Karen Kramer, children in most hunter-gatherer societies work just an hour or two per day, mostly foraging, hunting, fishing, collecting firewood, and helping with domestic tasks such as food processing.39 In contrast, a subsistence farmer’s children work on average between four to six hours a day (the range is from two to nine hours) doing gardening, tending animals, hauling water, collecting firewood, processing food, and doing other domestic tasks. In other words, child labor has an ancient agricultural history because children are needed for their substantial contributions to a family’s economic success, especially on a farm. Child labor also helps teach youngsters the skills they will need as adults. Today "
― Daniel E. Lieberman , The Story of the Human Body: Evolution, Health, and Disease
77
" typical adult’s resting metabolism requires about 1,300 to 1,600 calories a day, but this cost varies widely, largely because of variations in fat-free body mass (bigger bodies consume more energy).2 The remainder of your energy budget is spent doing things, primarily being physically active, but also digesting and keeping a stable body temperature. If you lounge about in bed all day you can stay in energy balance by ingesting just a fraction more than your resting metabolic demands. If, however, you decide to run a marathon, you’ll need an additional 2,000 to 3,000 calories. "
― Daniel E. Lieberman , The Story of the Human Body: Evolution, Health, and Disease
