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This study aims to develop age-at-death standards for Valley of Mexico skeletal collections. Using 159 individuals, with a dental age-at-death between 0 to 15 years, we develop linear and quadratic inverse regression models of age-at-death estimation between dental age and the diaphyseal length of the six long bones. A blind test for both regressions was performed, also a regression developed for a Maya group was carried out. We also compared skeletal growth of our sample by applying regressions developed for Maya and North American populations to assess the magnitude of the differences among ethnically unrelated populations. Our regressions yielded a close correlation between the diaphyseal length and dental age, especially femur and radius. It is noticeable that the disparities between younger and older age categories, the latter presenting larger standard deviations. Quadratic regression fitted better than linear and Maya regressions, and the differences of age-at-death distributions are significant. The skeletal growth curve of the Valley of Mexico is statistically different from other Native American groups. We conclude that for the present standards, despite the high degree of variance, the quadratic regression is a better applicable age estimator, when it is applied to biologically close populations.

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We identified mitochondrial DNA haplogroups A, B, C, and D in 75 present-day Maya individuals, 24 Maya individuals of the colonial period, and 1 pre-Columbian Maya individual from Quintana Roo, Mexico. We examined these data together with those of 21 Maya populations reported in the literature, comprising 647 present-day Maya individuals and 71 ancient Maya individuals. A demographic study based on analysis of fertility and endogamy was carried out in two modern Maya populations to identify cultural factors that influence the mitochondrial haplogroup genetic diversity. Most present-day and ancient Maya populations show a distribution pattern of mitochondrial haplogroup frequencies A, C, B, and D in decreasing order, with haplogroup D absent in several populations. Considering only modern Maya populations with at least 50 individuals analyzed, the present-day Tzotzil and Lacandon populations from Chiapas show the highest and lowest genetic diversity, 0.706 and 0.025, respectively. Our results show small genetic differences between the Maya populations, with the exception of the present-day Tojolabal and Lacandon populations from Chiapas. The present-day Lacandon population from Chiapas differs from other Maya populations in showing almost only haplogroup A. This result suggests a long history of isolation and endogamy as well as a possible founder effect inside the Lacandonian rain forest. The contemporary Tojolabal population is the only one with an unusual mitochondrial haplogroup pattern, exhibiting a frequency of haplogroup B higher than A and the absence of haplogroup C. With a small sample size, the pre-Columbian Copán Maya show a high content of haplogroup C and a low frequency of haplogroup D. The genetic homogeneity of the Maya populations is indicative of a common origin and nearly continuous gene flow in the long term within a general isolation of the whole group, in contrast to the Nahua populations that had different origins. Our demographic study showed high fertility rates and high levels of endogamy in the present-day Maya populations from Quintana Roo that are consistent with their general low genetic diversity. We propose that the genetic similarity among ancient and present-day Maya populations persists due to a strong sense of social cohesion and identity that impacts their marriage practices, keeping this cultural group isolated. These factors have constrained gene flow inside the Maya region and have impeded the differentiation among the Maya. Discernment of genetic differentiation within the peninsula is constrained by the lack of sampling documentation in the literature.

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OBJECTIVES: The goal of this study is to compare both dental and skeletal stress indicators of the Classic and Postclassic coastal and inland sites of the State of Quintana Roo, Mexico. The hypothesis is that coastal populations will show osteo and dental pathologies characteristic of a primarily marine food source combined with a diet of horticultural resources. This kind of alimentation provides people with less environmental stress and therefore a better health status. However, over time, in the Postclassic period, the health conditions deteriorated among both coastal and inland inhabitants, according to the hierarchization of the society, militarization, and commercial activities of all the coastal sites. METHODS: The sample was drawn from 19 sites (196 individuals of both sexes) from the east coast of the Yucatan Peninsula, as well as from inland localities within the boundaries of Quintana Roo. Both dental and osteological stress indicators were analyzed, and crosstabs were applied for absolute and relative frequencies and their corresponding χ(2) and F Fisher analyses. The osteopathological index of the coastal and inland sites of the Classic period were compared over time between the Classic coastal inhabitants and the Postclassic coastal inhabitants so as to understand how life conditions changed over time. The Mantel-Haenszel odds ratio, with the crosstabs controlling for sex (males and females), was also carried out. RESULTS: There are low frequencies of dental pathologies and anemia present in both the coastal and inland populations of Quintana Roo in the Classic and Postclassic times. Only the presence of periostitis is highly common in both types of site, and this is the only indicator with significant differences. The dental pathologies, anemia and periostitis, in general, present a slight upward trend in both the coastal and inland populations over time. The coastal populations have fewer frequencies of the above than the inland sites whilst, in the Postclassic period, both the coastal and inland sites register increased frequencies of all the indicators. Linear enamel hypoplasia (LEH) is the only indicator that does not follow this tendency. CONCLUSIONS: The analyzed indicators are in accord with the general tendency reported in the literature. The results revealed a general trend whereby the Classic inland sites display poorer life conditions than the Classic coastal sites. In the Postclassic period, this pattern changed because the frequencies of all stress indicators increased. The explanations regarding this tendency are related to the differential access to food resources between regions; coastal people had a varied diet and better sources of protein, taking into account the culture of alimentation, the type, and the sources (in general, fish) that have an important impact on the absorption of micronutrients and therefore greater impact on local health conditions. Also, it is plausible that they were able to access imported food through commerce (such as meat and vegetables/corn). The decline in health of the coastal people in the Postclassic period was probably associated with social stratification, increasing militarism, changes in the economic corpus, new pathogens, and the decline of the power structures prevailing throughout the Classic period.

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OBJECTIVES: The purpose of this study was to determine if commercial agriculture can lead to changes in peasant reproductive strategies in migrant agriculturalists from Calakmul, Campeche, Mexico. METHODS: The reproductive histories of 746 women from Calakmul, Campeche, Mexico were collected. The sample was first divided into women who had reproduced within or outside of Calakmul (RC and RO, respectively) and these were further subdivided into those who lived in households practicing subsistence agriculture and those who turned agriculture into a business (Household Subsistence Agricultural Strategy (HSA) and Household Commercial Agricultural Strategy (HCA), respectively). Age-specific fertility rate (ASFR) differences were compared between strategies and place of reproduction. Comparisons between interbirth interval and age at which desired fertility was reached were done with a Kaplan-Meier life table-based statistic. RESULTS: In both strategies, RC women increased ASFRs by reducing age at first birth, and HSA-RC women also reduced interbirth intervals. HCA women had lower ASFRs than HSA women. The latter had a natural fertility pattern while the former expressed a desire to stop reproducing at a younger age. HCA-RC women showed important fertility reductions after age 25 and HCA-RO women after age 30. CONCLUSIONS: Fertility reductions in households that practice commercial versus those that practice subsistence agriculture were significant. Also, a "frontier" effect was observed that increased fertility over all, but HCA households were not as influenced by it.

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