Daily Archives: May 7, 2008

The consequences of agriculture on the human body.

An absolutely fascinating paper, not written by me!

The Consequences of Domestication and Sedentism

Emily A. Schultz & Robert H. Lavenda

(This interesting piece on the effects of agriculture is from the college textbook Anthropology: A Perspective on the Human Condition Second Edition. pp 196-200)

Sedentism and domestication, separately and together, transformed human life in ways that still affect us today.

“Our Land”

Sedentism and domestication represent not just a technological change but also a change in worldview. Land was no longer a free good, available to anyone, with resources scattered randomly across the landscape; it was transformed into particular territories, collectively or individually owned, on which people raised crops and flocks.  Thus, sedentism and a high level of resource extraction (whether by complex foraging or farming) led to concepts of property tat were rare in previous foraging societies. Graves, grave goods, permanent housing, grain-processing equipment, as well as the fields and herds, connected people to places.  The human mark on the environment was larger and more obvious following sedentization and the rise of farming; people transformed the landscape in more dramatic ways–building terraces or walls to hold back floods.

Fertility, Sedentism, and Diet

One of the more dramatic effects of settling down was the change in female fertility and the rise in population.  A number of different effects together caused the population to grow.

Child Spacing Intervals   Among modern foragers, a woman’s pregnancies tend to be spaced three to four years apart because of the extended period of breastfeeding characteristic of these societies.  Extended means not just that children are weaned at three to four years of age but that they still nurse whenever they feel like it, as frequently as several times an hour (Shostak 1981, 67).  This nursing stimulus triggers the secretion of a hormone that suppresses ovulation (Henry 1989, 41). Henry points out that, “the adaptive significance of such a mechanism is obvious in the context of mobile foraging. A single child, who must be carried for some 3 to 4 years, creates a heavy burden for the mother; a second or third child within this interval would create an unmanageable problem for her and also jeopardize her health.

There are many reasons that nursing continues for three to four years in foraging societies. The foraging diet is high in protein, low in carbohydrates, and lacks soft foods easily digestible by very young infants. In fact, Marjorie Shostak observes that among Ju/’hoansi (!Kung), a contemporary foraging people of the Kalahari Desert, bush foods are rough and difficult to digest:  “To survive on such foods a child would have to be older than two years–preferably substantially older.” (1981, 66).  (See EthnoProfile 19.1: Ju/’hoansi [!Kung]).  By having her child nurse exclusively for six months, a mother does not have to find and prepare food for the infant in addition to her ordinary routine. Among the Ju/’hoansi, infants over the age of six months are given solid foods in the form of prechewed or pounded foods, a supplement that begins the transition to solid food (67).

The length of time between children in foraging societies serves to maintain a long-term energy balance in women during their reproductive years.  In many foraging societies, adding the caloric requirements of nursing to the physical demands of mobility, and the burden of food-gathering in the context of a high-protein, low-carbohydrate diet can keep the mother’s energy balance low. Where nutritional circumstances are marginal, the period of pregnancy and nursing can even constitute a net energy drain, resulting in a sharp drop in fertility. Under such circumstances, it will take the woman longer for her to regain her fertile condition. Thus, the period when she is neither pregnant nor nursing frequently becomes essential to building up her energy balance for future reproduction.

Fertility Rate Changes   In addition to the effects of breastfeeding, Ellison notes, age, nutritional status, energy balance, diet, and exercise all affect female fertility in a graduated way (1990).  That is, intense aerobic exercise may lead to the loss of the monthly period (amenorrhea), but less intense aerobic exercise may disrupt fertility in less obvious but still significant ways.

Recent studies of North American women who engage in high levels of endurance exercise (long-distance runners and young ballet dancers, for example) demonstrate several effects on childbearing.  These data are relevant to the transition to sedentism, because the levels of activity of the women studied approach the levels of activity of women in modern foraging societies.

Researchers found two different kinds of effects on fertility. Young, highly active ballet dancers studied by Warren (cited in Henry 1989) experienced their first menstruation at about 15.5 years, much later than a nondancing control group, whose members first menstruation was at about 12.5 years. High levels of exercise also seem to affect the endocrine system, reducing the time during which a woman is fertile by about one-third.

Summarizing the effects of foraging on female fertility, Henry observes:

It would appear then that a number of interrelated factors associated with a mobile foraging strategy are likely to have provided natural controls on fertility and perhaps explain the low population density of the Paleolithic. In mobile foraging societies, women are likely to have experienced both long intervals of breastfeeding by carried children as well as the high energy drain associated with subsistence activities and periodic camp moves.  Additionally, their diets, being relatively rich in proteins, would have contributed to maintaining low fat levels, thus further dampening fecundity. (1989, 43)

With complex foraging and increasing sedentism, these brakes on female fecundity would have been eased.  The duration of the breastfeeding period would have declined, as would the energy drain on women (Ju/’hoansi women, for example walk about 1,500 miles per year, carrying about 25 pounds of equipment, gathered food, and young children). This is not to say that a sedentary life is physically undemanding. Farming requires its own heavy labor, both from men and women. The difference seems to be in the kind of physical activity involved. Walking long distances carrying heavy loads and children was replaced by sowing, hoeing, harvesting, storing, and processing grain.  A diet increasingly rich in cereals would have significantly changed the ratio of protein to carbohydrate in the diet.  This would have changed the levels of prolactin, increased the positive energy balance, and led to more rapid growth in the young and an earlier age of first menstruation.

The ready availability of ground cereals would have enabled mothers to feed their infants soft, high-carbohydrate porridges and gruels. The analysis of infant fecal material recovered from the Wadi Kubbaniya site in Egypt seems to demonstrate that a similar practice was in use with root crops along the Nile at what may have been a year-round site by 19,000 years before the present (Hillman 1989, 230). The influence of cereals on fertility has been observed by Richard Lee among settled by Ju/’hoansi, who recently began to eat cereals and experienced a marked rise in fertility.  Renee Pennington (1992) notes that the increase in Ju/’hoansi reproductive success seems to be related to a reduction in infant and child mortality rates.

The Decline in the Quality of Diet

Westerners have long seen agriculture as an evolutionary advance over foraging, a sign of human progress. Put simply, however, early farmers did not eat as well as foragers. Jared Diamond (1987) writes:

While farmers concentrate on high carbohydrate crops like rice and potatoes, the mix of wild plants and animals in the diets of surviving hunter-gatherers provides more protein and a better balance of other nutrients. In one study, the San [Ju/’hoansi] average daily food intake (during a month when food was plentiful) was 2,140 calories and 93 grams of protein, considerably greater than the recommended daily allowance for people of their size.  It’s almost inconceivable that San [Ju/’hoansi] who eat 75 or so wild plants, could die of starvation the way hundreds of thousands of Irish farmers and their families did during the potato famine of the 1840s.

Skeletal evidence makes the same point. Skeletons from Greece and Turkey in late Paleolithic times indicate an average height of 5 feet 9 inches for men and 5 feet 5 inches for women. With the adoption of agriculture, the average height declined sharply; by about 5,000 years ago, the average male was about 5 feet 3 inches tall, the average woman, about 5 feet. Even modern Greeks and Turks are not, on average, as tall as the late Paleolithic people of the same region.

Increase in Precariousness

In the short term, agriculture was probably developed in ancient southwestern Asia, and perhaps elsewhere, to increase food supplies to support an increasing population at a time of serious resource stress. Over time, however, as dependence on domesticated crops increased, so did the overall insecurity of the food supply system. Why?

Proportion of Domesticated Plants in the Diet  There are several reasons why early farmers depended more and more on cultivated plants. Because the agroecology created an environment favorable to the plants, farmers were able to cultivate previously unusable land.  When such vital necessities as water could be brought to the land between the Tigris and Euphrates Rivers in Mesopotamia, land on which wheat and barley was not native could support dense stands of the domesticated grains.  Domestic plants also provided more and larger edible parts and were easier to harvest, process, and digest.  There is good evidence that they also tasted better. Rindos lists a number of modern food plants that derive from bitter wild varieties. Finally, the greater yield of domesticated plants per unit of ground also led to a greater proportion of cultivated plants in the diet, even when wild plants were still being eaten and were as plentiful as before.

Reliance on a Smaller Number of Plants   Unfortunately, reliance on an increasingly smaller number of plants is very risky should those plants fail.  According to Richard Lee, the Ju/’hoansi, who live in the Kalahari Desert, use over 100 plants (14 fruits and nuts, 15 berries, 18 species of edible gum, 41 edible roots and bulbs, and 17 leafy greens, beans, melons, and other foods; 1992b, 48).  By contrast, modern farmers rely on no more than 20 plants, and of those, three–wheat, maize, and rice–feed most of the world’s people.  Historically, it was only one or two grain crops that were the staple for a specific group of people.  A decrease in this crop has devastating effects on the population.

Selective Breeding, Monocropping, and the Gene Pool  Selective breeding of any given plant species decreases the variability of its gene pool, eliminating varieties with natural resistance to infrequently occurring pests and diseases and lowering its long-term survival chances by increasing the risk of severe losses at harvest time.  Again, the more people depend on a particular plant species, the riskier their future. Monocropping is the practice of growing only one kind of plant in a field. Although it increases efficiency and short-term yield, it exposes the entire field to destruction by diseases or pest damage. The outcome could be starvation.

Increasing Dependence on Plants  As cultivated plants took on an increasingly large role in their diet, people became dependent on plants and the plants in turn became completely dependent on the people–or rather on the environment created by the people. But the people could not completely control that environment. Hail, floods, droughts, infestations, frost, heat, weeds, erosion, and other factors could destroy or significantly affect the crop, yet all were largely outside human control.  The risk of failure and starvation increased.

Increase in Disease  Connected to the evolution of domesticated plants was an increase in disease, especially of the epidemic variety, for which there were several reasons.  First, prior to sedentism, human waste was disposed outside the living area. As increasing numbers of people began to live near each other in relatively permanent settlements, the disposal of human waste became increasingly problematic:  Large quantities of fecal material had the potential to transmit disease, and animal and plant wastes nourished pests, some of which served as disease vectors.

Second, a larger number of people living very near each other served as a disease reservoir.  Once a population is large enough, the likelihood of disease transmission increases.  By the time one person recovers from the disease, someone else reaches the infectious stage and can reinfect the first.  Consequently, the disease never leaves the population. The speed with which school children catch and spread colds, influenza, or chicken pox illustrates how a closely packed population and germs interact.

Third, settled people cannot just walk away from diseases; by contrast, if someone in a foraging band falls ill, the others can walk away, reducing the likelihood that the disease will spread.  Fourth, the agricultural diet may have reduced people’s resistance to disease. Finally, the rise in human population provided a greater opportunity for germs to evolve in human hosts. In fact, as we discussed in Chapter 3, there is good evidence that the clearing of land for farming in sub-Saharan Africa created an excellent environment for malaria-carrying mosquitos, leading both to a dramatic rise in human malaria and the selection for the HbAHbS genotype.

Environmental Degradation

With the development of agriculture, human beings began to intervene more actively in the environment.  Deforestation, soil loss, silted streams, and the loss of many native species followed domestication.  In the lower Tigris-Euphrates valley, irrigation waters used by early farmers carried high levels of soluble salts, poisoning the soil and making it unusable to this day.

Increase In Labor

Raising domesticated plants and animals requires much more labor than foraging.  People must clear the land, plant the seeds, tend the young plants, protect them from predators, harvest them, process the seeds, store them, and select the seeds for planting the next year; similarly, people must tend and protect domesticated animals, cull the herds, shear the sheep, milk the goats, and so on.


Diamond, Jared. 1987.  “The Worst Mistake in the History of the Human Race” Discover, May

Ellison, Peter. 1990.  “Human Ovarian Function and Reproductive Ecology: New Hypotheses” American Anthropologist 92 (4): 933-52

Henry, Donald. 1989.  From Foraging to Agriculture: The Levant and the End of the Ice Age  Philadelphia: University of Pennsylvania Press

Hillman, Gordon. 1989. “Late Paleolithic Plant Foods from Wadi Kubbaniya in Upper Egypt: Dietary Diversity, Infant Weaning, and Seasonality in a Riverine Environment.”  In Foraging and Farming: The Evolution of Plant Exploitation, edited by David Harris and Gordon Hillman, 207-39. Vol 13 of One World Archaeology.  London: Unwin Hyman.

Lee, Richard. 1992. The Dobe Ju/’hoansi  2d ed. New York: Holt, Rinehart and Winston.

Pennington, Renee. 1992.  “Did Food Increase Fertility: Evaluation of !Kung and Herero History” Human Biology  64: 497-501.

Shostak, Marjorie. 1981.  Nisa: The Life and Words of !Kung Woman  New York: Vintage Books

I feel I should add, that close contact with domesticated animals also brings us into contact with more nasty pathogens and parasites than a hunter gatherer would be exposed to.