R G Bribiescas
Biographic Data
| ID | 9250 |
|---|---|
| NAME | R G Bribiescas |
| GIVEN NAMES | R G |
| FAMILY NAME | Bribiescas |
| SIGNATURE | BRIBIESCAS R G |
| AFFILIATIONS | Yale University |
| ORCID | 0000-0002-8228-307X |
| VERIFIED | Yes |
| TOTAL WORKS | 40 |
| TOTAL CITATIONS | 114 |
| AUTHOR COUNT | 40 |
| EDITOR COUNT | 0 |
| FIRST PUBLICATION YEAR | 1996 |
| LATEST PUBLICATION YEAR | 2026 |
| H-INDEX | 6 |
Market Integration and Reproductive Transitions Among Indigenous Shuar and Neighboring Nonindigenous Ecuadorians in Amazonian Ecuador
OBJECTIVE: Global reproductive transitions are well documented, yet less is known about how neighboring populations with divergent histories and exposure to market integration (MI) experience them. This study examines how sociocultural and economic proxies of MI predict variation in reproductive outcomes among indigenous Shuar and nonindigenous Ecuadorian mestizos (Colonos) from Amazonian Ecuador, focusing on menarcheal age, age at first birth, p…
Navigating Practical, Political, and Ethical Challenges of Long‐Term Human Biology Field Research
Major advances in understanding human biology and health have been made possible by long‐term field research projects with Indigenous peoples, whose ecological settings and lifeways are distinct from majority populations in high‐income settings. Long‐term fieldwork is central to human biology, yet much about this research approach remains opaque. This paper considers a single long‐term study—the Shuar Health and Life History Project in Amazonian …
Reproductive Ecology and Evolutionary Anthropology
The research field of reproductive ecology continues to be a major contributor to the scientific advancement of evolutionary anthropology and human biology in general. Primary contributions to human evolutionary biology include a greater understanding of the physiological mechanisms that manage lifetime reproductive effort, resource allocation, life history trade-offs, demographic variation in fertility, the adaptive traits that define humans (Ho…
Nurturing Bonds
The information gained from the interviews and focus groups can be used to develop evidence-based messaging that strives to educate parents and caregivers to successfully identify hunger and satiety signals in infants and encourage the introduction of healthy and age-appropriate foods that complement current Samoan breastfeeding practices and childhood dietary patterns
Soil‐Transmitted Helminths and the Intricacies of Immunoregulation
OBJECTIVES: The old friends hypothesis (OFH) examines connections between the global increase in immunoregulatory diseases (e.g., allergy and autoimmunity) and reduced exposure to immune-priming symbionts like soil-transmitted helminths. Helminth species, however, vary in their effects on hosts and should be considered separately. We examined relationships between species-specific helminth infection and circulating biomarkers of adaptive immune a…
Testosterone, 8‐Oxo‐2′‐Deoxyguanosine (8‐OHdG) and Cu/Zn Superoxide Dismutase (SOD) in Adult Shuar Males of Amazonian Ecuador
Objectives Reproductive effort incurs the cost of biological aging and morbidity by compromising somatic maintenance when key resources are limited. Oxidative stress is positively correlated with reproductive effort in adult human females and non‐human male animal models, but human males are understudied. We hypothesized that due to its anabolic and metabolic promotion of reproductive effort in human males, testosterone would be positively associ…
Salivary Testosterone, Age, and Adiposity Associations Among Shuar Males in Amazonian Ecuador Challenge Assumptions of “Normal” Testosterone Patterns
Objectives Adult male testosterone concentrations in high income countries often decrease with age and adiposity, a pattern typically viewed as “normal.” However, testosterone is expected to be adaptively regulated within the range of resource constrained, high pathogen, natural fertility conditions across which it evolved to function. We therefore examine associations among testosterone diurnal variation, age, and adiposity among Indigenous Shua…
Associations between maternal and infant body composition, feeding practices, and perceived infant eating behaviour in Samoan mother–infant dyads aged 1–4 months
Maternal perception of infant appetite appears to be influenced partially by maternal and infant body composition and breastfeeding patterns in our sample, highlighting potential points of intervention to promote recommended breastfeeding practices
The impact of thawing duration on leptin and adiponectin levels in frozen human milk samples
BACKGROUND: Measurements of hormone concentrations in human milk from understudied populations across the world is of growing scientific interest. Due to limited access to suitable laboratory facilities at many research sites, human milk samples are often shipped frozen to distant laboratories for analysis. Shipping and handling exposes samples to the risk of thawing and degradation as the results of delays, mishandling, or other unforeseen circu…
Variation in diurnal cortisol patterns among the Indigenous Shuar of Amazonian Ecuador
This study expands the documented range of global variation in HPA axis activity and diurnal cortisol production and provides important insights into the plasticity of human stress physiology across diverse developmental and socioecological settings
Hierarchies in the energy budget
The evolution of human life history characteristics required dramatic shifts in energy allocation mechanisms compared with our primate ancestors. Thyroid hormones, such as thyroxine (T4) and triiodothyronine (T3), are sensitive to energy balance, and are significant determinants for both tissue‐specific and whole‐body metabolic rate. Thus, thyroid hormones are in part responsible for setting the body's overall energy budget and likely played an i…
Low prevalence of anemia among Shuar communities of Amazonian Ecuador
OBJECTIVE: Anemia is an important global health challenge. We investigate anemia prevalence among Indigenous Shuar of Ecuador to expand our understanding of population-level variation, and to test hypotheses about how anemia variation is related to age, sex, and market integration. METHODS: Hemoglobin levels were measured in a total sample of 1650 Shuar participants (ages 6 months to 86 years) from 46 communities between 2008 and 2017 to compare …
Replicability of leptin associations with testosterone, estradiol, follicle‐stimulating hormone, and luteinizing hormone in healthy Ache men of Paraguay
Objective Associations between leptin and male reproductive hormone levels have been reported in men. However, few of these investigations have focused on associations in healthy men without obesity or overweight or nonindustrial societies. Methods We test hypotheses that leptin is associated with testosterone, estradiol, luteinizing hormone (LH), and follicle‐stimulating hormone (FSH) within healthy Ache men, an indigenous nonindustrialized Sout…
Accelerated senescence as a cost of reproduction
Objectives Oxidative stress is hypothesized to contribute to age‐related somatic deterioration. Both reproductive and ecological context may necessitate tradeoffs that influence this outcome. We examined whether measures of lifetime reproductive effort were related to levels of oxidative stress biomarkers in peri‐ and post‐menopausal women and whether associations were moderated by rural or urban residence. Methods We surveyed 263 healthy women (…
C‐reactive protein in adult Samoans
These data are among the first to demonstrate CRP correlates in a sample of adult Samoans. CRP differed by sex and was associated with BMI, adiposity, and some cardiometabolic risk markers. These data align with findings in other populations
Evolutionary and Life History Insights into Masculinity and Warfare
Previous articleNext article FreeEvolutionary and Life History Insights into Masculinity and Warfare Opportunities and LimitationsRichard G. BribiescasRichard G. BribiescasPDFPDF PLUSAbstractFull Text Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinked InRedditEmailQR Code SectionsMoreAbstractIn this paper I present, evaluate, and discuss evidence that evolutionary and life history theory can inform o…
Aging, Life History, and Human Evolution
Aging occurs in all sexually reproducing organisms. That is, physical degradation over time occurs from conception until death. While the life span of a species is often viewed as a benchmark of aging, the pace and intensity of physical degradation over time varies owing to environmental influences, genetics, allocation of energetic investment, and phylogenetic history. Significant variation in aging within mammals, primates, and great apes, incl…
High energy requirements and water throughput of adult Shuar forager‐horticulturalists of Amazonian Ecuador
OBJECTIVES: We measured total energy expenditure (TEE; kcal/d) and water throughput (L/d) among Shuar forager-horticulturalists from Amazonian Ecuador to compare their daily energy and water demands to adults in other small-scale and industrialized populations. METHODS: TEE and water throughput were measured using the doubly labeled water method among 15 Shuar adults (eight women, seven men; age range 18-60 years) living in a relatively remote vi…
Soil‐transmitted helminth infection and intestinal inflammation among the Shuar of Amazonian Ecuador
OBJECTIVES: Little research exists documenting levels of intestinal inflammation among indigenous populations where exposure to macroparasites, like soil-transmitted helminths (STHs), is common. Reduced STH exposure is hypothesized to contribute to increased prevalence of elevated intestinal inflammation in wealthy nations, likely due to coevolutionary histories between STHs and human immune systems that favored anti-inflammatory pathways. Here, …
The cost of reproduction in women
OBJECTIVES: Life history theory predicts a trade-off between female investment in reproduction and somatic maintenance, which can result in accelerated senescence. Oxidative stress has been shown to be a causal physiological mechanism for accelerated aging and a possible contributor to this trade-off. We aimed to test the hypothesis for the existence of significant associations between measures of reproductive effort and the level of oxidative st…
Oxytocin and Epstein‐Barr virus
OBJECTIVES: The purpose of the study was to examine the relationship between self-reported stress levels among new mothers in São Paulo, Brazil and two biomarkers of stressful experience, oxytocin (OT) and Epstein-Barr Virus antibody level (EBV-ab), with planned pregnancy hypothesized as a moderator of biological response to stressful conditions. METHODS: Sixty-three first-time mothers between the ages of 15 and 45 were recruited from neighborhoo…
Diurnal variation in salivary cortisol across age classes in A che A merindian males of P araguay
Ache Amerindian men exhibit a flattening of the diurnal rhythm across age classes. Our results were able to capture both within- and between-individual variations in cortisol levels, and reflected age-related contrasts in daily cortisol fluctuations. The flattening of the diurnal rhythm with age among the Ache may reflect a common and shared aspect of male senescence across ecological contexts and lifestyles. Am. J. Hum. Biol. 27:344-348, 2015. ©…
Relationships between biomarkers of inflammation, ovarian steroids, and age at menarche in a rural polish sample
Inflammation itself may suppress ovarian function, or indicate immune challenges that lead to ovarian suppression. The timing of menarche may also influence adult inflammatory sensitivity and ovarian hormone concentrations. This lends support to existing models of trade-offs between maintenance and reproduction in women
Male Life History, Reproductive Effort, and the Evolution of the GenusHomo
The evolution of male life history traits was central to the emergence of the genus Homo. Compared with earlier hominins, changes in the behavioral and physiological mechanics of growth, survivorship, reproductive effort, and senescence all likely contributed to shifts in how males contributed to the evolution of our genus. For example, the range of paternal investment in modern Homo sapiens is unusual compared with most mammals and primates, all…
An evolutionary and life history perspective on the role of males on human futures
Testosterone levels among Aché hunter-gatherer men
Male Life History, Reproductive Effort, and the Evolution of the GenusHomo
The evolution of male life history traits was central to the emergence of the genus Homo. Compared with earlier hominins, changes in the behavioral and physiological mechanics of growth, survivorship, reproductive effort, and senescence all likely contributed to shifts in how males contributed to the evolution of our genus. For example, the range of paternal investment in modern Homo sapiens is unusual compared with most mammals and primates, all…
Serum leptin levels and anthropometric correlates in Ache Amerindians of eastern Paraguay
Leptin is a recently discovered peptide hormone secreted primarily from adipocytes in humans and other mammals; it is a reflection of fat stores, and has been associated with reproductive function. However, few leptin measurements are available from nonindustrialized populations, including contemporary hunter/gatherer communities undergoing the transition to sedentary agriculture. This investigation reports single‐sample serum leptin measurements…
Age-related differences in serum gonadotropin (FSH and LH), salivary testosterone, and 17-? estradiol levels among Ache Amerindian males of Paraguay
Age-related differences in serum luteinizing hormone (LH), follicle-stimulating hormone (FSH), salivary testosterone, and 17-beta estradiol levels are reported for Ache Amerindian males (n = 17; mean age, 37.1 +/- 14.2 SD) of Paraguay in order to explore population variation in patterns of male reproductive senescence in a foraging/agricultural community. Hormone associations were examined to test various hypotheses for age-related differences in…
Endometrial thickness is not independent of luteal phase day in a rural Polish population
The endometrium is important for luteal phase function, implantation, placentation, and gestation. Endometrial morphology has been shown to impact early pregnancy success in in vitro fertilization and egg donor cycles and has been implicated in conception success in spontaneous cycles. However, few studies have monitored endometrial morphology in normo-ovulatory women or examined possible population variation in its physiology or thickness. Furth…
Evolutionary and Life History Insights into Masculinity and Warfare
Previous articleNext article FreeEvolutionary and Life History Insights into Masculinity and Warfare Opportunities and LimitationsRichard G. BribiescasRichard G. BribiescasPDFPDF PLUSAbstractFull Text Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinked InRedditEmailQR Code SectionsMoreAbstractIn this paper I present, evaluate, and discuss evidence that evolutionary and life history theory can inform o…
Soil‐transmitted helminth infection and intestinal inflammation among the Shuar of Amazonian Ecuador
OBJECTIVES: Little research exists documenting levels of intestinal inflammation among indigenous populations where exposure to macroparasites, like soil-transmitted helminths (STHs), is common. Reduced STH exposure is hypothesized to contribute to increased prevalence of elevated intestinal inflammation in wealthy nations, likely due to coevolutionary histories between STHs and human immune systems that favored anti-inflammatory pathways. Here, …
Aging, Life History, and Human Evolution
Aging occurs in all sexually reproducing organisms. That is, physical degradation over time occurs from conception until death. While the life span of a species is often viewed as a benchmark of aging, the pace and intensity of physical degradation over time varies owing to environmental influences, genetics, allocation of energetic investment, and phylogenetic history. Significant variation in aging within mammals, primates, and great apes, incl…
Associations between maternal and infant body composition, feeding practices, and perceived infant eating behaviour in Samoan mother–infant dyads aged 1–4 months
Maternal perception of infant appetite appears to be influenced partially by maternal and infant body composition and breastfeeding patterns in our sample, highlighting potential points of intervention to promote recommended breastfeeding practices
Hierarchies in the energy budget
The evolution of human life history characteristics required dramatic shifts in energy allocation mechanisms compared with our primate ancestors. Thyroid hormones, such as thyroxine (T4) and triiodothyronine (T3), are sensitive to energy balance, and are significant determinants for both tissue‐specific and whole‐body metabolic rate. Thus, thyroid hormones are in part responsible for setting the body's overall energy budget and likely played an i…
Testosterone levels among Aché hunter-gatherer men
Reproductive ecology and life history of the human male
Until recently, the reproductive ecology of human males has not been extensively investigated, primarily as a result of the need for a theoretical framework based on the reproductive constraints and energetics of mammalian males. More specifically, male reproductive ecology has necessitated an integrative interpretation of clinical and anthropological data based on the premise that the evolution of human male life histories has involved selection…
Reproductive ecology and life history of the human male
Until recently, the reproductive ecology of human males has not been extensively investigated, primarily as a result of the need for a theoretical framework based on the reproductive constraints and energetics of mammalian males. More specifically, male reproductive ecology has necessitated an integrative interpretation of clinical and anthropological data based on the premise that the evolution of human male life histories has involved selection…
Serum leptin levels and anthropometric correlates in Ache Amerindians of eastern Paraguay
Leptin is a recently discovered peptide hormone secreted primarily from adipocytes in humans and other mammals; it is a reflection of fat stores, and has been associated with reproductive function. However, few leptin measurements are available from nonindustrialized populations, including contemporary hunter/gatherer communities undergoing the transition to sedentary agriculture. This investigation reports single‐sample serum leptin measurements…
Effects of oral zinc supplementation on serum leptin levels in Ache males of eastern Paraguay
Significant population variation has been demonstrated in serum leptin levels, independent of adiposity. Included within these populations, Ache males have significantly lower leptin levels compared to American subjects with comparable adiposity. The underlying causes of these differences are not understood but zinc has been shown to be an important regulator of leptin in humans and rodents. Zinc deficiency is associated with somatic wasting and …
Serum leptin levels in Ache Amerindian females with normal adiposity are not significantly different from American anorexia nervosa patients
Serum leptin, a polypeptide hormone secreted primarily by adipocytes, is a reflection of somatic fat availability in humans and other vertebrates. Among Ache Amerindians, leptin levels are very low in contrast to other populations, despite comparable adiposity with individuals exhibiting much higher leptin levels. In order to gain a greater understanding of these differences, leptin levels were compared between Ache Amerindian females (n = 12, me…
Testosterone-mediated immune functions and male life histories
Recent advances in human life history theory have provided new insights into the potential selection pressures that were instrumental in the evolution of human and non-human primate males. However, gaps remain in our understanding of how primate males regulate and allocate energetic resources between survivorship and reproductive effort. Defense against parasitic infection is an important force shaping life history evolution. Proper performance o…
Age-related differences in serum gonadotropin (FSH and LH), salivary testosterone, and 17-? estradiol levels among Ache Amerindian males of Paraguay
Age-related differences in serum luteinizing hormone (LH), follicle-stimulating hormone (FSH), salivary testosterone, and 17-beta estradiol levels are reported for Ache Amerindian males (n = 17; mean age, 37.1 +/- 14.2 SD) of Paraguay in order to explore population variation in patterns of male reproductive senescence in a foraging/agricultural community. Hormone associations were examined to test various hypotheses for age-related differences in…
On the evolution, life history, and proximate mechanisms of human male reproductive senescence
Reproductive senescence is a central and defining life-history characteristic of every known mammal. Within the scope of human senescence research, attention has been mainly focused on females, particularly in reference to the uniqueness of menopause. However, consideration of the evolution of human male reproductive senescence has been minimal, primarily due to the assumption that male fertility, as compared to that of females, is relatively inv…
Men
Active ghrelin levels across time and associations with leptin and anthropometrics in healthy ache Amerindian women of Paraguay
Active (acylated) ghrelin is a peptide hormone secreted primarily by the stomach, positively associated with fasting, orexigenic, and promotes growth hormone secretion. It is therefore important to energy intake management. The objective of this pilot research was to (1) compare active ghrelin with previous measurements of leptin and anthropometrics; (2) assess the consistency of active ghrelin across time in this population; (3) extend our under…
Men
Specific gravity as an alternative to creatinine for estimating urine concentration in captive and wild chimpanzee ( Pan troglodytes ) Samples
The measurement of hormones in urine has become a widely used technique in primatology. Because urine concentration varies according to fluid intake, concentration must be measured in each sample collected, and hormone values are always expressed per unit of concentration. Traditionally, creatinine has been used as a concentration index, but some studies in humans have shown that creatinine varies among populations and even within and between ind…
Circadian variation in salivary testosterone across age classes in Ache Amerindian males of Paraguay
Testosterone levels exhibit a circadian rhythm in healthy men, with morning levels tending to be higher compared to evening titers. However, circadian rhythms wane with age. Although this has been described in males living within industrialized settings, age-related changes have not received similar attention in populations outside these contexts. Because many nonindustrialized populations, such as Ache Amerindians of Paraguay, exhibit testostero…
Endometrial thickness is not independent of luteal phase day in a rural Polish population
The endometrium is important for luteal phase function, implantation, placentation, and gestation. Endometrial morphology has been shown to impact early pregnancy success in in vitro fertilization and egg donor cycles and has been implicated in conception success in spontaneous cycles. However, few studies have monitored endometrial morphology in normo-ovulatory women or examined possible population variation in its physiology or thickness. Furth…
An evolutionary and life history perspective on the role of males on human futures
Male Life History, Reproductive Effort, and the Evolution of the GenusHomo
The evolution of male life history traits was central to the emergence of the genus Homo. Compared with earlier hominins, changes in the behavioral and physiological mechanics of growth, survivorship, reproductive effort, and senescence all likely contributed to shifts in how males contributed to the evolution of our genus. For example, the range of paternal investment in modern Homo sapiens is unusual compared with most mammals and primates, all…
Relationships between biomarkers of inflammation, ovarian steroids, and age at menarche in a rural polish sample
Inflammation itself may suppress ovarian function, or indicate immune challenges that lead to ovarian suppression. The timing of menarche may also influence adult inflammatory sensitivity and ovarian hormone concentrations. This lends support to existing models of trade-offs between maintenance and reproduction in women
Oxytocin and Epstein‐Barr virus
OBJECTIVES: The purpose of the study was to examine the relationship between self-reported stress levels among new mothers in São Paulo, Brazil and two biomarkers of stressful experience, oxytocin (OT) and Epstein-Barr Virus antibody level (EBV-ab), with planned pregnancy hypothesized as a moderator of biological response to stressful conditions. METHODS: Sixty-three first-time mothers between the ages of 15 and 45 were recruited from neighborhoo…
Diurnal variation in salivary cortisol across age classes in A che A merindian males of P araguay
Ache Amerindian men exhibit a flattening of the diurnal rhythm across age classes. Our results were able to capture both within- and between-individual variations in cortisol levels, and reflected age-related contrasts in daily cortisol fluctuations. The flattening of the diurnal rhythm with age among the Ache may reflect a common and shared aspect of male senescence across ecological contexts and lifestyles. Am. J. Hum. Biol. 27:344-348, 2015. ©…
The cost of reproduction in women
OBJECTIVES: Life history theory predicts a trade-off between female investment in reproduction and somatic maintenance, which can result in accelerated senescence. Oxidative stress has been shown to be a causal physiological mechanism for accelerated aging and a possible contributor to this trade-off. We aimed to test the hypothesis for the existence of significant associations between measures of reproductive effort and the level of oxidative st…
High energy requirements and water throughput of adult Shuar forager‐horticulturalists of Amazonian Ecuador
OBJECTIVES: We measured total energy expenditure (TEE; kcal/d) and water throughput (L/d) among Shuar forager-horticulturalists from Amazonian Ecuador to compare their daily energy and water demands to adults in other small-scale and industrialized populations. METHODS: TEE and water throughput were measured using the doubly labeled water method among 15 Shuar adults (eight women, seven men; age range 18-60 years) living in a relatively remote vi…
Soil‐transmitted helminth infection and intestinal inflammation among the Shuar of Amazonian Ecuador
OBJECTIVES: Little research exists documenting levels of intestinal inflammation among indigenous populations where exposure to macroparasites, like soil-transmitted helminths (STHs), is common. Reduced STH exposure is hypothesized to contribute to increased prevalence of elevated intestinal inflammation in wealthy nations, likely due to coevolutionary histories between STHs and human immune systems that favored anti-inflammatory pathways. Here, …
Aging, Life History, and Human Evolution
Aging occurs in all sexually reproducing organisms. That is, physical degradation over time occurs from conception until death. While the life span of a species is often viewed as a benchmark of aging, the pace and intensity of physical degradation over time varies owing to environmental influences, genetics, allocation of energetic investment, and phylogenetic history. Significant variation in aging within mammals, primates, and great apes, incl…
Accelerated senescence as a cost of reproduction
Objectives Oxidative stress is hypothesized to contribute to age‐related somatic deterioration. Both reproductive and ecological context may necessitate tradeoffs that influence this outcome. We examined whether measures of lifetime reproductive effort were related to levels of oxidative stress biomarkers in peri‐ and post‐menopausal women and whether associations were moderated by rural or urban residence. Methods We surveyed 263 healthy women (…
Biology (29 works) · Medicine (22 works) · Endocrinology (17 works) · Population (17 works) · Evolutionary Psychology and Human Behavior (14 works) · Internal Medicine (13 works) · Demography (12 works) · Hormone (11 works) · Ecology (9 works) · Life history theory (9 works)