Agriculture Reference
In-Depth Information
diseases were not caused by eating domesticated plants, they did become preva-
lent when the conditions were established that would promote the maintenance and
spread of the pathogens that caused them, namely, close, crowded, unsanitary living
conditions associated with permanent or semipermanent communities that focused
their food production on crops. It is these circumstances that set in motion the later
evolution of pathogens and spread of contagious diseases caused by them, such
as smallpox, measles, whooping cough, black death, leprosy, and other diseases,
some of which are quite recent (e.g., HIV/AIDS, severe acute respiratory syndrome
[SARS], Ebola).
In addition to pathogens causing infectious disease, in many settings involving
sedentary living in settlements, water sources are also easily contaminated by para-
sites. Humans who drink water containing parasites, such as hookworm, become
infected. These parasites can result in severe anemia, resulting in a range of health
problems, including decreased cognitive abilities and work capacity (various authors
mentioned in Beard and Stoltzfus 2001). In a range of settings, prehistoric agri-
cultural populations show pathology associated with iron deficiency anemia called
porotic hyperostosis
. Iron deficiency anemia causes the expansion of the region of
the skeleton involving red blood cell production. As a result, the flat bones of the
skull (and sometimes eye orbits) become more porous. The iron deficiency is caused
by parasitic infection, consumption of iron-poor foods, or consumption of foods con-
taining phytate (e.g., corn), which inhibits iron metabolism (Larsen 1997).
There are other skeletal indicators that show a decline in health in early agricul-
turalists. Dental caries (tooth decay) is a progressive disease process involving the
demineralization of the tooth enamel and underlying structures (see Larsen 1997,
Hillson 2008, for discussion of archaeological, historical, and ethnographic settings).
It is caused by acids produced as a by-product of the metabolism of dietary carbo-
hydrates (sugars especially) by naturally occurring oral bacteria (e.g.,
Streptococcus
mutans
). Most profound in this regard, sugars and other carbohydrates (e.g., starches)
generally are cariogenic, resulting in an increase in tooth decay and various other
oral problems that give way to infections and tooth loss. A trend of increasing fre-
quency of dental decay with agriculture has been documented worldwide (vari-
ous authors as mentioned in Cohen and Armelagos 1984, Steckel and Rose 2002,
Cohen and Crane-Kramer 2007). These increases have been associated with various
grains, but corn appears to be exceptionally cariogenic (e.g., Larsen et al. 1991). In
contrast, early rice producers in East Asia show very little or no increase in caries
relative to foragers (e.g., Domett 2001, Pietrusewsky and Douglas 2002, Oxenham
2006, Oxenham et al. 2005, Temple and Larsen 2007; although see Pechenkina et al.
2002). Rice-based diets appear to be less cariogenic than those involving other staple
cereals (Sreebny 1983).
Perhaps the most dramatic impact of agriculture is seen in the negative effects that
the transition to farming had on growth and development. The presence of enamel
defects caused by growth disruption—a pathology called
enamel hypoplasia
—shows
a general pattern of increase in frequency in comparison of prehistoric foragers and
farmers. Enamel hypoplasia, areas of enamel deficiency usually appearing as hori-
zontal lines or grooves, is a nonspecific stress indicator, arising from either disease
or poor nutrition or a combination of both during the years of enamel development
