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Differential investment in offspring by parental and progeny gender has been discussed and periodically analyzed for the past 80 years as an evolutionary adaptive strategy. Parental investment theory suggests that parents in poor condition have offspring in poor condition. Conversely, parents in good condition give rise to offspring in good condition. As formalized in the Trivers-Willard hypothesis (TWH), investment in daughters will be greater under poor conditions while sons receive greater parental investment under good conditions. Condition is ultimately equated to offspring reproductive fitness, with parents apparently using a strategy to maximize their genetic contribution to future generations. Analyses of sex ratio have been used to support parental investment theory and in many instances, though not all, results provide support for TWH. In the present investigation, economic strategies were analyzed in the context of offspring sex ratio and survival to reproductive age in a Zapotec-speaking community in the Valley of Oaxaca, southern Mexico. Growth status of children, adult stature, and agricultural resources were analyzed as proxies for parental and progeny condition in present and prior generations. Traditional marriage practice in Mesoamerican peasant communities is patrilocal postnuptial residence with investments largely favoring sons. The alternative, practiced by ~25% of parents, is matrilocal postnuptial residence which is an investment favoring daughters. Results indicated that sex ratio of offspring survival to reproductive age was related to economic strategy and differed significantly between the patrilocal and matrilocal strategies. Variance in sex ratio was affected by condition of parents and significant differences in survival to reproductive age were strongly associated with economic strategy. While the results strongly support TWH, further studies in traditional anthropological populations are needed. Am J Phys Anthropol 143:501-511, 2010. [c] 2010 Wiley-Liss, Inc. KEY WORDS sex ratio; offspring survival; Trivers-Willard hypothesis; Oaxaca DOI 10.1002/ajpa.21333

Secular change in adult height of residents in a rural indigenous community in the Valley of Oaxaca was evaluated. Subjects were measured in 1971 (49 males, 26 females 19-70 years), 1978 (128 males, 124 females 19-82 years) and 2000 (155 males, 255 females 19-89 years). Heights were adjusted for estimated loss with age using two protocols; height at 21 years of age was also estimated. The effects of age and secular factors on measured and adjusted heights were evaluated through segmented linear regressions for three birth periods, KEY WORDS stature; indigenous populations; auxological epidemiology; health; living conditions; nutritional status DOI 10.1002/ajpa.21167

The objective of the present study is to analyze age-specific mortality in a rural indigenous community in the throes of a secular increase in size in the Valley of Oaxaca, southern Mexico, over 30 years, 1970-1999. Variation in mortality by age group was analyzed over time for evidence of an epidemiological transition. The seasonal rain pattern in the Valley of Oaxaca (83% from May through September) was evaluated for its relationship with mortality in wet and dry months. Mortality and causes of death changed markedly over the 30-year interval. Infant and preschool mortality, overall mortality, and causes of death changed from the 1970s through the 1990s. Prereproductive deaths ( KEY WORDS prereproductive mortality; demographic transition; secular trends; gastrointestinal disease; nutritional status; seasonal variation

The objective of this investigation was to analyze the underlying cause(s) of secular changes in craniofacial dimensions among indigenous children in an isolated community in Oaxaca, southern Mexico, between 1968-2000. Subjects were schoolchildren resident in a rural, agrarian, Zapotec-speaking community in the Valley of Oaxaca, previously characterized as mildly-to-moderately undernourished with growth-stunting in 1968 and 1978. In 2000, children had experienced a secular increase in height compared with two prior growth surveys. Four craniofacial dimensions (head length, head breadth, and bizygomatic and bigonial breadths) were measured during anthropometric surveys of schoolchildren aged 6-13 years in 1968, 1978, and 2000. Cephalic and zygomandibular indices were calculated. Samples by survey were: 1968, 151 males and 157 females; 1978, 179 males and 184 females; and 2000, 180 males and 186 females. The analysis was based on a total of 1,037 children. Multivariate analysis of covariance was used to assess secular trend effects, with height, age, and [age.sup.2] as covariates by sex. Over the interval of 32 years, significant secular changes occurred in craniofacial dimensions and one index: 1) head length was shorter in boys and girls; 2) bizygomatic breadth was narrower in boys and girls; 3) head breadth increased over time only among girls; 4) brachycephalization increased significantly in a linear manner among both sexes; and 5) the zygomandibular index decreased significantly only in boys. Thus, the cranial complex remodeled to a shorter head length, both relatively (brachycephalization) and absolutely. Remodeling over time also resulted in a narrower face, with the midface changing at about the same rate as the lower face (i.e., mandible). Secular changes are generally recognized as multifactorial. Changes in the cephalic index and cranium over time in schoolchildren in an isolated rural agrarian Zapotec-speaking community in the Valley of Oaxaca suggest that the underlying forces for the secular change are associated: 1) decreased food (maize) coarseness or grit content (masticatory stress), and 2) relaxed natural selection, resulting in 3) a greater role for developmental plasticity. KEY WORDS head length; head breadth; bigonial breadth; bizygomatic breadth; cephalic index; brachycephalization; secular increase; Zapotec Indians

Objective To test the hypothesis that secular changes in body size and age at menarche are related to the demographic and epidemiologic transitions in an indigenous community in Oaxaca, southern Mexico. Methods Data were derived from surveys of a Zapotec-speaking community conducted between 1968 and 2000. Segmented linear regressions of height, weight, BMI and recalled age at menarche on year of birth in cohorts of adults born before and after the demographic transition were used to evaluate secular changes. Corresponding comparisons of body size (MANCOVA controlling for age) and age at menarche (status quo, probit analysis) were done for samples of children and adolescents born before and after the epidemiological transition. Results Height and weight increased in adults born after the demographic transition (mid-1950s), and especially in children and adolescents born after the epidemiological transition (mid-1980s). Age at menarche also decreased significantly in women born after the demographic transition, but at a more rapid estimated rate in adolescents born after the epidemiological transition. Secular gains in body weight were proportional to those for height among children and adolescents, but adults, males more so than females, gained proportionally more weight. Conclusions The secular trend in height in adults of both sexes was associated with the decade of the demographic transition in the mid-1950s. Significant secular gains in size attained and age at menarche occurred in children and youth born after the epidemiologic transition which likely reflected improved health and nutritional conditions since the mid-1980s. [ABSTRACT FROM AUTHOR]

Objective This study tests the hypothesis that natural selection is associated with type 2 diabetes (T2D)-associated mortality and fertility in a rural isolated Zapotec community in the Valley of Oaxaca, southern Mexico. Participants and Methods Mortality data and related demographic and genealogic information were linked with data for fertility, prereproductive mortality and family history of mortality attributed to T2D. Physician verified T2D mortality ( n = 27) between 1980 and 2009 and imputed T2D ( n = 70) from cardiovascular mortality (68% random sample) and renal failure (44% random sample). Bootstrapping was used to obtain a robust variance estimate in survival analysis and multivariate analysis of variance. Results Estimated maximum natural selection by Crow's Index occurred circa 1930 and was relaxed after this time in the study population. Cox-regression survival analysis of T2D mortality with covariates (family history of T2D, cardiovascular disease, renal failure) indicated a significant hazard ratio (HR = 5.95, 95% CI: 1.38-25.67, p < .008) for the increase in T2D in 2000 to 2009. Survival analysis of imputed T2D resulted in a significant HR of 2.03 (95% CI: 1.08-3.85, p = .01) for the increase in T2D in the 2000 to 2009 cohort (reference group: 1980-1989). Mean number of live born offspring was lower among T2D ( n = 27, 4.04 ± 3.85 SD) compared to non-T2D ( n = 199, 5.30 ± 3.48) groups ( p < .08). Mean number of live born offspring was lower ( p = .003) among imputed T2D compared to non-T2D groups (4.10 ± 3.44 vs. 5.62 + 3.50). Discussion T2D-associated mortality increased in frequency as natural selection decreased, and favored offspring survival of non-T2D descedants. The results indicated statistically significant directional selection against T2D and imputed T2D to this population isolate. [ABSTRACT FROM AUTHOR]