302 CHAPTER 13 | Human Adaptation to a Changing Worldparents genetically; therefore, size differences between im-
migrant children and their parents could be attributed to
the environment alone. This kind of difference, known as
a secular trend, allows anthropologists to make inferences
about environmental effects on growth and development.
For example, across the globe tremendous variation is
seen in the age at menarche (first menstruation). Some
of this variation can be attributed to genetically based
population differences, while the remainder is due to en-
vironmental effects. The Bundi of New Guinea have the
oldest average age (18) at menarche. An important theory
accounting for the timing of sexual maturation ties age
at menarche to the percentage of body fat possessed by
growing individuals as a regulator of hormonal produc-
tion. Hormones impact fertility into adulthood, but teas-
ing apart the role of biology and culture with respect to
hormones has proven to be complex. Take, for example,
the case of androgen hormone levels, waist-to-hip ratio,When challenged by malnutrition, physical growth slows
to permit immediate survival at the expense of height in
adulthood. This adaptive mechanism may have negative
consequences for subsequent generations as individuals
who were malnourished as children have been shown to
experience reduced reproductive success as adults.^3
Boas also demonstrated differences in the growth of
immigrant children in the United States compared to their
parents. This work was the earliest documentation of the
variable effects of different environments on the growth
process. Presumably, immigrant children resemble theirAnthropologist of NotePeter Ellison
Reproductive biology and human health
across cultures have been the focus of
the work of biological anthropologist
Peter Ellison. In the 1970s, Ellison first
read Darwin’s Origin of Species as a
college student at St. John’s College in
Annapolis, Maryland. He found Darwin’s
text transformative and went to theUniversity of Vermont to study biology;
later he earned a doctorate in biological
anthropology from Harvard, where he
now runs a comprehensive program in
reproductive ecology.
Ellison has pioneered techniques
for hormonal analysis from saliva, and
he uses this technique to monitorindividuals’ hormonal response to a vari-
ety of environmental stressors. This non-
invasive technique has allowed Ellison
to conduct hormonal studies throughout
the world and to correlate hormonal lev-
els with social events. People from long-
term field sites in Congo, Po land, Japan,
Nepal, and Paraguay have participated
in this research, allowing
Ellison to document the
hormonal variation around
biological events, such as
egg implantation and breast-
feeding, as well as cultural
factors such as farm work or
foraging.
He is especially in-
terested in how behavior
and social stimuli affect
reproductive physiology. In
Western societies, he has
explored hormonal levels
of males and females in
response to stimuli, such as
winning a championship or
taking a stressful exam. He
has also studied the relation-
ship cancer development
has to exercise and stress.
In his recent book On Fertile
Ground, Ellison illustrates
how evolutionary forces have
shaped human reproductive
physiology into a system ca-
pable of precise responses to
environmental stimuli.Peter Ellison (left) and Peter Gray discuss how male testosterone levels differ between married and
single men and among men of different cultures.© Kris Snibbe/Staff Photo Harvard News Office(^3) Martorell, R. (1988). Body size, adaptation, and function. GDP, 335–347.
secular trend A physical difference among related people from
distinct generations that allows anthropologists to make infer-
ences about environmental effects on growth and development.
10843_13_p298-321.indd 30210843_13_p298-321.indd 302 1/20/10 1:21:30 AM1/20/10 1:21:30 AM