The Discovery of Sex j 1515 15
was compensated by high caloric intake, high energy expenditure alone might interfere
with the body’s ability to allocate food energy to reproduction. According to the authors,
this is because “a woman’s ability to meet the metabolic cost of pregnancy and lactation
depends on her ability to down- regulate her own metabolic requirements.” When this abil-
ity is affected by high workload, a temporary suppression of ovulation may be an adaptive
mechanism, preventing pregnancy when the body is under physical stress.
Because wild food resources are seldom uniformly available at all times and places,
hunter- gatherer societies tend to develop regular patterns of group movement, aggrega-
tion, and dispersal that are synchronized with the annual fluctuations of food abundance,
variety, and availability. Inevitably, this results in periods of abundance interspersed with
periods of hunger. From the standpoint of women’s fertility, the combination of prolonged
nursing and high energy expenditure (during harvesting or migration) may have combined
to suppress ovulation, thus lowering the birthrate at these times. The birthrate would thus
increase during periods of plenty when the group settled in one place for a time and decrease
in lean times when the group migrated in search of resources. Instead of being associated
with sexual intercourse, cycles in the birth rate would have correlated with periods of abun-
dance and leisure, especially for women.
Another factor that may have obscured the causal relationship between copulation and
childbirth is prepuberty sexual activity. In studies of the Dobe Ju of Botswana (1963– 76),
Richard Lee found that sex education of children began at a young age.^12 Children slept
under the same blanket with their parents and were thus exposed to their parents having
sexual intercourse. Sexual play was considered a normal part of childhood, and nearly all
boys and girls had some sexual experience, including intercourse, by age 15. Of course, preg-
nancy only resulted if both partners had passed through puberty.
A similar attitude toward children’s sexual activity by the Trobriand Islanders was
observed in the early twentieth century by Bronislaw Malinowski.^13 Not surprisingly, given
the cultural attitudes of the period, many of his interpretations have had to be revised.
Nevertheless, Malinowski’s accounts are still the best record we have of Trobriand Islander
beliefs and customs at something close to the pre- contact state.
In a paper published in 1916 entitled Baloma; the Spirits of the Dead in the Trobriand
Islands, Malinowski reported that sexual activity among the Trobriand Islanders began
well before puberty and that both sexes were expected to have many lovers before marriage:The sexual freedom of unmarried girls is complete. They begin intercourse with the
other sex very early, at the age of six to eight years. They change their lovers as often as
they please, until they feel inclined to marry. Then a girl settles down to a protracted
and, more or less, exclusive intrigue with one man, who, after a time, usually becomes
her husband.^14Under such an arrangement, instances are bound to occur when an unmarried girl
becomes pregnant, but when Malinowski inquired of his informants “who was the father of
an illegitimate child,” he received the circular answer that there was no father because the
girl was not married. When he pursued the point and asked who was the biological father,
his question drew a blank. In Malinowski’s day, at least, Trobriand Islanders had no concept