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traits arising from southwestern Yunnan’s disease environment that
conferred a greater resistance, ifby no means total immunity, on indi-
genous peoples.^76 Hemoglobin genetic disorders are a human response
to southwestern Yunnan’s disease environment.
Swidden agriculture may have helped to produce this environment by
making malaria endemic. Frank B. Livingstone’s classic anthropological
study of this connection in West Africa indicated that the employment of
iron tools for swiddening effectively increased the breeding ground
forAnopheles gambiae, the regional falciparummalariavector.Swid-
dening increased the density of human populations and reduced shaded
areas avoided by the insects to expand the blood supply and space
available for A. gambiae’s reproduction. Incidence of the defensive
human genetic adaptation of sickle-cell anemia increased in response.
Livingstone also showed a lower incidence of malaria and genetic
adaptations among foragers who do not practice swiddening and who,
therefore, had not accidentally built a disease environment in response
to local ecology. One 1932 study foundA. gambiaenumbers actually
increased when a forest was cut down and dropped during subsequent
reforestation. Similar environmental dynamics may also have been
operative in southwestern Yunnan. The affinity of certainAnopheles
species for environments transformed by humans would help explain
the persistence of regional malarial ties despite the radical terraforming
by Han cultivation.^77
In sum, observations by Qing subjects and Nationalist citizens
regarding the superior resistance of southwestern provincials to the most
lethal form of malaria endemic to the region has a basis in current
scientific understanding. A 1943 study of the disease in Mangshi
confirmed a much higher incidence of chronic malaria among Chinese
than among indigenous residents. Of course, it is necessary to qualify
observations that tend to overgeneralize in racial terms and so can easily
give the false impression that Han residence in southwestern Yunnan’s
malarial disease environment was impossible in all circumstances. Some
accounts note the particular susceptibility of“migrants”(liuyu). Yet, in at
least one instance, Ortai demonstrated his own understanding that resist-
ance to malaria was not so determined and thus did not constitute an
immutable distinction between Han and local peoples. In 1726 , respond-
ing to fears that a proposed site of walled construction in Yuanjiang
prefecture might be malarial, he pointed out that Yuanjiang had been
underjunxian, and, so, Han, control since 1660. Over time,“both gentry
and commoners”had become“acclimated”(xiguan) to the disease.^78
196 Across Forest, Steppe, and Mountain
