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Hemoglobin Genotype and Fertility in a Malarial Environment: Limon, Costa Rica
Madrigal-Diaz, Lorena
Madrigal-Diaz, Lorena
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Abstract
This dissertation tests the hypothesis of differential
fertility of Hb AS females in a malarial environment. The
biocultural factors that affect achieved reproduction in this
sample are examined. The aim of the research is to document the
action of natural selection through differential fertility, and
the interaction of culture and biology to produce achieved
fertility.
Epidemiological, clinical and in vitro studies indicate that
Hb AS individuals experience low malarial morbidity and mortality.
Thus, natural selection increases the frequency of hemoglobin S
through differential mortality when the selective agent is
malaria. However, it has also been proposed (Livingston, 1957)
that the high frequency of hemoglobin S in malarial environments
may be the result of differential mortality and reproduction.
Pirscheinfs work (1961, 1984) suggests that Hb AS women have higher
fertility in a malarial environment because Hb AA mothers suffer
more frequent abortions as a result of placental malaria.
Fertility data and blood sample were collected from 159 black
women from the coastal town of Limon, Costa Rica. This
investigation indicates that there are no significant differences
between Hb AS and Hb AA mothers in terms of live births (t=-0.69,
ns, df=98), completed family size (t=0.79, ns, df=98) or abortions
(t=0.61, ns, df=93).
The analysis of the reproductive data identifies the main
biocultural factors that affect achieved fertility in the Limon
population. In this sample, age at menarche is significantly
correlated with the number of abortions (r=-0.28, p< 0.005)
indicating that early menarche increases the risk of fetal
wastage. Women with completed family size above average are
different from their peers only in the number of pregnancies and
livebirths. A path analyses of the fertility data allows the
examination of the causal structure of achieved fertility in the
sample. The path analyses indicates that the number of multiple
births and abortions influence the completed family size mainly
through their correlation with the number of pregnancies.
In conclusion, this dissertation does not support the
hypothesis of differential reproduction of Hb AS and Hb AA females
in a malarial environment. This study confirms prior indications
that the Hb S polymorphism has been maintained solely through
differential mortality. In contrast with previous research, this
dissertation incorporates biological and cultural components of
completed fertility. Achieved fertility in Limon is influenced by
the age at menarche, the number of pregnancies, and the number of
abortions. The age at marriage does not influence the reproductive
outcome.
Description
The University of Kansas has long historical connections with Central America and the many Central
Americans who have earned graduate degrees at KU. This work is part of the Central American Theses
and Dissertations collection in KU ScholarWorks and is being made freely available with permission of the
author through the efforts of Professor Emeritus Charles Stansifer of the History department and the staff of
the Scholarly Communications program at the University of Kansas Libraries’ Center for Digital Scholarship.
Date
1988-06-09
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University of Kansas
Archive Status
This item contains archived web content.
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Madrigal-Diaz_1988.pdf
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