318 CHAPTER 13 | Human Adaptation to a Changing Worlda variety of ailments ranging from acne to prostate cancer.
Moreover, DES was routinely added to animal feed. It was
not until 1971, however, that researchers realized that DES
causes vaginal cancer in young women. Subsequent studies
have shown that DES causes problems with the male repro-
ductive system and can produce deformities of the female
reproductive tract of individuals exposed to DES in utero.
DES mimics the natural hormone, binding with appropri-
ate receptors in and on cells, and thereby turns on biological
activity associated with the hormone.^21
DES is not alone in its effects: At least fifty-one
chemicals—many of them in common use—are now
known to disrupt hormones, and even this could be the tip
of the iceberg. Some of these chemicals mimic hormones
in the manner of DES, whereas others interfere with other
parts of the endocrine system, such as thyroid and testos-
terone metabolism. Included are such supposedly benign
and inert substances as plastics widely used in laboratories
and chemicals added to polystyrene and polyvinyl chlo-
ride (PVCs) to make them more stable and less breakable.
These plastics are widely used in plumbing, food process-
ing, and food packaging.
Hormone-disrupting chemicals are also found in many
detergents and personal care products, contraceptive
creams, the giant jugs used to bottle drinking water, and
plastic linings in cans. About 85 percent of food cans in the
United States are so lined. Similarly, the harmful health con-
sequences of the release of compounds from plastic wrap
and plastic containers during microwaving are now known,
though for many years using plastic in the microwave was
an acceptable cultural practice. Similarly, bisphenol-A
(BPA)—a chemical widely used in water bottles and baby
bottles (hard plastics)—has recently been associated with
higher rates of chronic diseases such as heart disease and
diabetes, and it has been shown to disrupt a variety of other
reproductive and metabolic processes. Infants and fetuses
are at the greatest risk from exposure to BPA.
While there is consensus in the scientific community
and governments are starting to take action (the Canadian
government declared BPA a toxic compound), removing this
compound from the food industry may be easier that ridding
the environment of this contaminant. For decades billions of
pounds of BPA have been produced each year, and in turn it
has been dumped into landfills and bodies of water. As with
the Neolithic revolution and the development of civilization,
each invention creates new challenges for humans.
The implications of all these developments are sober-
ing. We know that pathologies result from extremely low
levels of exposure to harmful chemicals. Yet, besides those
used domestically, the United States exports millions
of pounds of these chemicals to the rest of the world.^22warming, our species needs to evolve new cultural tools
in order to anticipate environmental consequences that
eventuate over decades. Regulating human population
size globally and using the earth’s resources more conser-
vatively are necessary to ensure our survival.
Global warming is merely one of a host of problems
today that will ultimately have an impact on human gene
pools. In view of the consequences for human biology of
such seemingly benign innovations as dairying or farming
(as discussed in Chapter 10), we may wonder about many
recent practices—for example, the effects of increased ex-
posure to radiation from use of x-rays, nuclear accidents,
production of radioactive waste, ozone depletion (which
increases human exposure to solar radiation), and the like.
Again the impact is often most severe for those who
have not generated the pollutants in the first place. Take, for
example, the flow of industrial and agricultural chemicals
via air and water currents to Arctic regions. Icy tempera-
tures allow these toxins to enter the food chain. As a result
toxins generated in temperate climates end up in the bodies
(and breast milk) of Arctic peoples who do not produce the
toxins but who eat primarily foods that they hunt and fish.
In addition to exposure to radiation, humans also face
increased exposure to other known mutagenic agents,
including a wide variety of chemicals, such as pesticides.
Despite repeated assurances about their safety, there have
been tens of thousands of cases of poisonings in the United
States alone and thousands of cases of cancer related to the
manufacture and use of pesticides. The impact may be
greater in so-called underdeveloped countries, where sub-
stances banned in the United States are routinely used.
Pesticides are responsible for millions of birds being
killed each year (many of which would otherwise be hap-
pily gobbling down bugs and other pests), serious fish
kills, and decimation of honey bees (bees are needed for
the efficient pollination of many crops). In all, pesticides
alone (not including other agricultural chemicals) are
responsible for billions of dollars of environmental and
public health damage in the United States each year.^20 An-
thropologists are documenting the effects on individuals,
as described in the Biocultural Connection feature.
The shipping of pollutant waste between countries
represents an example of structural violence. Individuals
in the government or business sector of either nation may
profit from these arrangements, creating another obstacle
to addressing the problem. Similar issues may arise within
countries, when authorities attempt to coerce ethnic mi-
norities to accept disposal of toxic waste on their lands.
Hormone-disrupting chemicals are of particular concern
because they interfere with the reproductive process. For ex-
ample, in 1938 a synthetic estrogen known as DES (diethyl-
stilbestrol) was developed and subsequently prescribed for(^21) Colburn, T., Dumanoski, D., & Myers, J. P. (1996). Hormonal sabotage.
Natural History 3, 45–46.
(^20) Pimentel, D. (1991). Response. Science 252, 358.^22 Ibid., 45–46.
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