312 CHAPTER 13 | Human Adaptation to a Changing WorldMcKenna conducted a series of experiments document-
ing differences between the brainwave patterns of mother–
infant pairs who co-sleep compared to mother–infant pairs
who sleep in separate rooms. These data fit McKenna’s
theory, challenging North America’s predominant cultural
practice of solitary sleeping. Further, McKenna shows how
the cultural pattern of sleeping directly impacts infant feed-
ing practices, demonstrating that co-sleeping and breast-
feeding are mutually reinforcing behaviors.
Evolutionary medicine suggests that cultural practices
in industrial and postindustrial societies are responsible
for a variety of other biomedically defined diseases, rang-
ing from psychological disorders to hepatitis (inflamma-
tion of the liver).Symptoms as Defense Mechanisms
Scientists have documented that when faced with infec-
tion from a bacterium or virus, the human body mounts a
series of physiological responses. For example, as a young
individual learns his or her culture’s medical system, the
person might learn to recognize an illness as a cold or flu
by responses of the body, such as fever, aches, runny nose,
sore throat, vomiting, or diarrhea.
Think of how you may have learned about sickness as
a young child. A caregiver or parent might have touched
your forehead or neck with the back of the hand or lips to
gauge your temperature. Maybe you had a thermometer
placed under your arm or in your mouth to see if you had
an elevated temperature or fever. (In the past, young chil-
dren’s temperatures were usually taken rectally in North
America.) If any of these methods revealed a temperature
above the value defined as normal, a medicine might have
been given to lower the fever.
Evolutionary medicine proposes that many of the
symptoms that biomedicine treats are themselves nature’s
treatments developed over millennia. Some of these symp-
toms, such as fever, perhaps should be tolerated rather
than suppressed, so the body can heal itself. An elevated
temperature is part of the human body’s response to in-
fectious particles, whereas eliminating the fever provides
favorable temperatures for bacteria or viruses. Similarly
within some physiological limits, vomiting, coughing, and
diarrhea may be adaptive as they remove harmful sub-
stances and organisms from the body. In other words, the
cultural prescription to lower a fever or suppress a cough
might actually prolong the disease.
Evolutionary biologist Margie Profet proposes a par-
ticular benefit for the symptoms of nausea and vomiting
during early pregnancy.^12 She suggests that many plants,While diseases are generally described in biological terms
as understood through scientific investigation, the medical
anthropological framework admits that notions of disease
are not universal. Each culture’s medical system provides
individuals with a “map” of how to think about themselves
in sickness and health. All cultures define specific terms and
mechanisms for thinking about, preventing, and managing
illness. In this way, Western medical systems define whether
a particular bio logical state such as malnutrition, Down syn-
drome, or schistosomiasis is recognized as an illness. Each
cultural system delineates the choices and constraints avail-
able to individuals afflicted by particular disease states.Evolutionary Medicine
Evolutionary medicine—an approach to human sickness
and health combining principles of evolutionary theory
and human evolutionary history—draws from both sci-
entific medicine and anthropology. While it may seem
at first to concentrate on human biological mechanisms,
evolutionary medicine’s emphasis is true to the biocultural
integration that figures so prominently in anthropologi-
cal approaches. In this approach, biological processes are
given cultural meanings, and cultural practices are under-
stood to affect human biology.
As with evolutionary theory in general, it is difficult
to prove conclusively that specific ideas and theories
from evolutionary medicine are indeed beneficial to hu-
man health. Instead, scientists work to amass a sufficient
body of knowledge that supports their theories. Where
appropriate, the theories can lead to hypotheses that can be
tested experimentally. Frequently treatments derived from
evolutionary medicine lead to alterations in cultural prac-
tices and to a return to a more natural state in terms of hu-
man biology. As described in the Biocultural Connection
in Chapter 9, evolutionary medicine has contributed to
current attitudes about the diseases of civilization.
The work of biological anthropologist James Mc-
Kenna is an excellent example of evolutionary medicine.
McKenna has suggested that the human infant, immature
compared to some other mammals, has evolved to co-
sleep with adults who provide breathing cues to the sleep-
ing infant, protecting the child from sudden infant death
syndrome (SIDS).^11 He uses cross-cultural data of sleeping
patterns and rates of SIDS to support his claim.(^11) McKenna, J. (1999). Co-sleeping and SIDS. In W. Trevathan, E. O. Smith, &
J. J. McKenna (Eds.), Evolutionary medicine. London: Oxford University Press.
(^12) Profet, M. (1991). The function of allergy: Immunological defense against
toxins. Quarterly Review of Biology 66 (1), 23–62; Profet, M. (1995). Protect-
ing your baby to be. New York: Addison Wesley.
evolutionary medicine An approach to human sickness and
health combining principles of evolutionary theory and human
evolutionary history.
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