Agriculture Reference
In-Depth Information
heAlth And the AgRIcultuRAl RevolutIon
Two key things stand out in the shift from foraging to farming that have implica-
tions for health. First, human population size increased wherever the event occurred.
Moreover, these populations shifted from seasonal (and sometimes year-round)
mobility to living in semipermanent or permanent communities. In other words,
preagricultural populations were small and dispersed, whereas agricultural popula-
tions were larger, more sedentary, and living in closer, more crowded conditions.
Second, the quality of diet changed. Prehistoric foragers generally ate a more varied
diet, and farmers ate an increasingly narrow diet. As these plants became more and
more central to diet, the nutritional quality of diet declined. Thus, there are both
indirect (change in pattern of settlement) and direct (change in nutritional quality)
consequences of the foraging-to-farming transition.
In terms of the impact of declining mobility and population concentration, a range
of skeletal indicators reveals that in many areas of the world there was an elevation in
the prevalence of pathology associated with infection and infectious disease (Cohen
and Armelagos 1984, Steckel and Rose 2002, Walimbe and Tavares 2002, Oxenham
et al. 2005, Cohen and Crane-Kramer 2007, and others; see reviews in Cohen 1989,
Larsen 1995, 2003). In addition, while evidence of chronic infectious disease was
certainly present in early foragers, perhaps even with great antiquity (Kappelman
et al. 2008), it is virtually nonexistent. Skeletal evidence of chronic infectious dis-
ease—such as syphilis, tuberculosis, and leprosy—are primarily associated with
agricultural-based populations living in close, densely crowded communities. This
appears to be the case in large part because it creates the conditions conducive to the
spread of infectious disease. Most pathogens—bacteria and viruses—causing infec-
tious disease require ready transport from host to host to survive. Close proximity
to humans and marginal sanitation are perfect for these kinds of circumstances. In a
wide range of archaeological settings, limb bones of skeletons display characteristic
lesions called
periosteal reactions
. These lesions give the surface of the bone a rough
texture and sometimes lead to noticeable elevation and expansion of the bone. The
lesions are caused by local infections, such as that resulting from an infected cut or
abrasion. In crowded, reduced-sanitation conditions, there is a much greater chance
for bacteria (e.g.,
Staphylococcus aureus
) to spread to the wound, infecting the limb,
including the bone. On the other hand, any injury to the outer surface of bone can
lead to periosteal reactions. However, there is a clear pattern of general increase
in early agriculturalists compared to their hunter-gatherer forebears. Most of these
lesions documented by anthropologists are nonspecific. We really do not know the
specific cause and can only conclude that their increase signals a decline in health.
Some lesions, however, are specific insofar as the pattern of infection is character-
istic of a specific infectious disease. For example, in eastern North America, tibia
(lower leg) bones are swollen and bowed, and skulls have distinctive cavitations
that are symptomatic of a group of diseases called
treponematosis
, which includes
venereal syphilis, nonvenereal (endemic) syphilis, and yaws. Various late prehistoric
agricultural societies pre-dating the arrival of Columbus have lesions characteristic
of a nonvenereal form of treponematosis. It is only during the early contact era soon
following the arrival of Columbus that the disease became venereal. While these
