EFFECTS OF STRESS ON ONSET OF MIDDLE CHILDHOOD AMONG SIDAMA ...

182 Pages·2015·1.95 MB·English

EFFECTS OF STRESS ON ONSET OF MIDDLE CHILDHOOD

AMONG SIDAMA AGROPASTORALISTS

By

COURTNEY ELIZABETH HELFRECHT

A dissertation submitted in partial fulfillment of
the requirements for the degree of

DOCTOR OF PHILOSOPHY

WASHINGTON STATE UNIVERSITY
Department of Anthropology

MAY 2016

© Copyright by COURTNEY ELIZABETH HELFRECHT, 2016
All Rights Reserved
© Copyright by COURTNEY ELIZABETH HELFRECHT, 2016
All Rights Reserved
To the Faculty of Washington State University:
The members of the Committee appointed to examine the dissertation of
COURTNEY ELIZABETH HELFRECHT find it satisfactory and recommend
that it be accepted.

Courtney L. Meehan, Ph.D., Chair

Edward H. Hagen, Ph.D.

Barry S. Hewlett, Ph.D.

Robin M. Bernstein, Ph.D.

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ACKNOWLEDGEMENTS

I have worked with hundreds of people over the years it has taken to see this degree to
completion and I am grateful to so many. First and foremost, I must thank the Sidama, Aka, and
Ngandu families who welcomed me into their lives and answered my numerous questions. This
research would not be possible without their contributions. Along those lines, I am also
extremely grateful to Filate Fissa, Sisay Belete, Samuel Dira, Mulye Girma, Rhobot Tamiru,
Marije Raedts, and the many other friends I made in Ethiopia for their kindnesses and essential
assistance in the field. I am also indebted to Aubain Mongosso, Edouard Mboula, Matthieu
Banzengola, Alain Kolet, Marius Mouguia, and my many other friends in the Central African
Republic. I am additionally grateful to the National Science Foundation (BCS #1260428) for
funding my research.
To my committee - Courtney Meehan, Ed Hagen, Barry Hewlett, and Robin Bernstein –
thank you. Barry, your knowledge and experience have contributed so much more than you
likely realize to my research and goals. Thank you for your willingness to provide substantive
and thoughtful feedback over these many years. Ed, I could not have completed this project
without your assistance. I aspire to be an educator who is as supportive and available as you.
Robin, your enduring optimism, kindness, and intelligence have been a guiding light. Courtney,
you have been a mentor, a teacher, and a friend. Working with you has been a privilege and I
cannot even begin to fully express my gratitude for the many opportunities you have provided
me. Thank you so very much. I am also deeply indebted to David DeAvila and the WSU/UI
Center for Reproductive Biology for their generous assistance with my hormone analyses.
Although not the goal of pursuing this degree, I have made so many wonderful friends
whose support, encouragement, and humor have made this experience so much more fulfilling
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than I could possibly have ever expected. Thank you to Jennifer Wilcox Roulette, Sarah Council,
Angela Sulfaro, Jen Ferris, Ryan Szymanski, Faith Njeri, Alissa Miller, Kelly Derr, Annette
Ruzicka, Kristin Safi, Ethan McGaffey, Mark Remiker, and so many others - your friendship has
made this journey a whole lot lighter.
To my family – John, Oriana, Natascha, Mom, Dad, Jessica, and Kristen - I am so
grateful to have had you by my side. This experience has not been without its challenges, but
your support, your understanding and flexibility, and your faith in me have helped see it to
completion. Thank you for being the most wonderful partner, children, parents, and sisters in all
the world. There are no words that can express my thankfulness for you.

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EFFECTS OF STRESS ON ONSET OF MIDDLE CHILDHOOD

AMONG SIDAMA AGROPASTORALISTS

Abstract

by Courtney Elizabeth Helfrecht, Ph.D.
Washington State University
May 2016

Chair: Courtney L. Meehan

Current research suggests that human childhood evolved as a phase of assessment, where
children use experience with their social and physical environments to determine future
development and reproductive strategies. Yet, few studies have empirically tested this hypothesis
and much of the research examining the evolution of childhood focuses on infancy or
adolescence, leaving a significant gap in our understanding of middle childhood, a period
comprising one-third of our development. To address this gap, this dissertation examines the
relationship between stress and middle childhood among Sidama agropastoralists of
southwestern Ethiopia. Data on age categories, social and cognitive development, and
cultural/physical stressors were collected from both adults and children. In addition, hair samples
from 160 children (aged 3-18 years old) were collected to assess two biomarkers (cortisol and
dehydroepiandrosterone sulfate [DHEAS]), along with anthropometrics and demographic data.
As in most cultures, onset of Sidama middle childhood (shiima beto) coincides with onset
of reason. The primary stressor believed to affect children is a shortage of economic resources,
and the impact of this is reflected in hair cortisol concentrations (HCC). Average age of onset for
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adrenarche is slightly delayed in comparison to Western populations, but examination of the
associated biomarker (DHEAS) revealed an unexpected pattern—involution of the adrenal fetal
zone is significantly delayed, indicating important variation from known life history patterns.
Additionally, analyses examining differences in DHEAS concentrations based on HCC and
nutritional status found that girls with lower HCC, but not boys, deviated from the sample-level
pattern, expressing a relatively flattened line for DHEAS following the early childhood decline.
This study contributes novel data both on two biomarkers, extending our understanding
of the range for “normal” child development, and on adrenarche in an environment where
nutritional stress and extrinsic mortality are high. It additionally provides ethnographic data on
age categories, stressors, and socio-cognitive development during middle childhood among
Sidama agropastoralists. The results demonstrate not only that stress impacts patterns of
ontogeny during middle childhood, but also the importance of integrating biology, culture, and
ecology if we are to fully understand the role of stress in shaping the evolution of human life
history.

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TABLE OF CONTENTS

ACKNOWLEDGEMENTS ....................................................................................................... iii-iv
ABSTRACT ................................................................................................................................ v-vi
LIST OF TABLES ...................................................................................................................... x-xi
LIST OF FIGURES ...................................................................................................................... xii
CHAPTER
1. INTRODUCTION ............................................................................................................... 1
Objectives ............................................................................................................... 3
Organization ............................................................................................................ 5
2.LIFE HISTORY THEORY .................................................................................................. 7
Life History Theory ................................................................................................ 7
Human Juvenility .................................................................................................... 8
Life History Stages across Development .............................................................. 10
Stress and Life History.......................................................................................... 16
3. MIDDLE CHILDHOOD AND ADRENARCHE ............................................................. 20
Middle Childhood ................................................................................................. 20
Adrenarche ............................................................................................................ 23
4. BIOMARKERS AND HAIR HORMONE ANALYSIS .................................................. 28
Anthropology and hormone analysis .................................................................... 29
Hair hormone analysis .......................................................................................... 30
Hair sampling as a field-friendly alternative ........................................................ 33
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5. SIDAMA AGROPASTORALISTS OF LOKE ................................................................ 36
6. RESEARCH GOALS AND HYPOTHESES .................................................................... 50
Goal 1 .................................................................................................................... 51
Goal 2 .................................................................................................................... 52
Goal 3 .................................................................................................................... 52
Goal 4 .................................................................................................................... 53
Goal 5 .................................................................................................................... 54
Goal 6 .................................................................................................................... 54
7. METHODS ........................................................................................................................ 55
Cultural Age Categories across the Lifespan ........................................................ 56
Cognitive Transition and Social Development during Middle Childhood ........... 57
Cultural and Environmental Stressors .................................................................. 58
Biomarker (Cortisol and DHEAS) Collection and Analysis ................................ 59
Analysis Strategies ................................................................................................ 64
8. RESULTS – CULTURAL AGE CATEGORIES ............................................................. 66
9. RESULTS – COGNITIVE AND SOCIOCULTURAL DEVELOPMENT ..................... 74
Cognitive Transition at Middle Childhood ........................................................... 74
Cognitive and Social Development across Middle Childhood ............................. 76
10. RESULTS – STRESS ...................................................................................................... 82
11. REUSLTS – ADRENARCHE AND MIDDLE CHILDHOOD...................................... 92
Summary Statistics................................................................................................ 92
Hair Cortisol Concentrations ................................................................................ 97
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Stressors and Hair Cortisol Concentrations ........................................................ 101
Hair DHEAS Concentrations .............................................................................. 104
Onset of Adrenarche ........................................................................................... 106
Onset of Middle Childhood ................................................................................ 107
Adrenarche and Middle Childhood ..................................................................... 108
Puberty Scores and Hair DHEAS Concentrations .............................................. 109
12. RESULTS – EFFECTS OF STRESS ON ONSET OF MIDDLE CHILDHOOD AND
ADRENARCHE .................................................................................................................. 111
13. DISCUSSION AND CONCLUSIONS ......................................................................... 116
Discussion ........................................................................................................... 116
Limitations and future research .......................................................................... 129
Conclusions ......................................................................................................... 131
REFERENCES ........................................................................................................................... 133
APPENDIX
A. CORTISOL, DHEAS, AND ANTHROPOMETRIC DATA .................................................165

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