The Combined DNA Index System (CODIS) loci comprise a standard microsatellite marker set widely used for distinguishing among individuals in forensic DNA identity testing for medicolegal casework in the United States and in other countries. In anthropological genetic research, CODIS markers have become an important tool for uses extending beyond case investigations to quantify ancestry proportions, reveals patterns of admixture, and trace population histories. These investigations are especially prevalent in studies of Latin American population structure. Nevertheless, the accuracy of the ancestry estimates computed from the CODIS loci for highly admixed Latino populations has not been formally tested. Longstanding arguments have been made that small ancestry panels, including the CODIS loci specifically, are not suitable for ancestry inference in admixed populations, due to high heterozygosity and limited number of loci used. Recent studies on ancestry inference using the CODIS loci suggest that these do confer more information of population-level identifiability than recognized in forensic genetic scholarship and by the medicolegal community. Here, we formally test the ability of CODIS and CODIS-proxy (e.g., high-heterozygosity and individual-identifiability loci) marker panels to accurately estimate admixture proportions of individuals, including a sample of Latinos with a wide range of ancestry proportions. Using the same individuals to make direct comparisons of the outcomes, the authors produced ancestry estimates from (a) a small CODIS/CODIS-proxy locus panel and (b) a robust and validated microsatellite ancestry-informative panel. They found evidence (e.g., ρ = 0.80–0.88) that supports the use of CODIS/ CODIS-proxy loci to capture the general ancestry estimation trends of a sample. This finding is in line with results of studies using CODIS on Latin American populations: the ancestry estimations generated by CODIS present trends supported by documented population histories (e.g., colonialism and population movements) and microevolutionary events (e.g., gene flow) in Latin America. However, this study also highlights the limitations of CODIS for making individual-level inferences of ancestry: the associated estimates for an acceptable level of statistical confidence (95%) are too broad to make any nuanced inferences regarding an individual's actual ancestry composition.

In this study, we investigated, for the first time from a forensic anthropological perspective, the question of mixed ancestry estimation for modern Filipinos with geographic origins in the Philippines. We derived estimates of continental ancestry using craniometrics from four sources: a new documented collection of current forensic significance from the Manila North Cemetery; the Howells cranial series representing a sample of unclaimed individuals from Manila but said largely to originate from more remote areas, with dates of death before 1940; the Hanihara sample aggregated from various locations and time periods across the Philippines; and the Hanihara series capturing various local indigenous, ethnic groups that are together identified as Philippine Negrito. Parental craniometrics were selected from the Howells data set and more recently collected samples from Europe and Asia. Using unsupervised clustering, we investigated the algorithmically defined three-cluster, or trihybrid admixture, model to infer continental ancestry for each individual, reporting their relative proportions of Asian, European, and African admixture. We used similar clustering procedures to identify more complex models, with a larger number of clusters, to explore patterns of affinity between our four Philippine samples and the recently acquired samples from Vietnam, Thailand, China (Hong Kong), Japan, and Korea. These analyses give insight into the relationships between both macro- and microgeographic regions, revealing at the country level how different population dynamics—whether political, economic, historical, and/or social—structure the ancestral makeup of Asian peoples, especially in the degree of European and African admixture. From these ancestry estimates, we found that population of origin explains 38–51% of the variation in each ancestry component, and we detected significant differences among the Asian samples in their quantities of ancestry. Filipinos appear considerably admixed, as they carry almost 20% less Asian ancestry than the average quantity (90%) estimated for the other Asian groups. We also revealed substructure within our representation of modern Filipinos, such that differences in the patterns of three-way admixture exist between each of the four Philippine samples; the Manila cemetery sample had the highest level of Asian ancestry, and, as we might expect, the Negrito sample had the greatest quantity of African ancestry. We performed additional analyses that introduced craniometrics from the Howells Australo-Melanesian series, to more fully investigate their relationship to the Asian samples and to better understand the African contributions common to the Philippine Negritos especially, as well as the other Southeast Asians and the Spanish and Portuguese groups. By mapping the cluster patterns on a global scale, these analyses reveal that, with craniometrics just as with genetic loci, patterns of affinity are informative of the complex history of Southeast Asia, as they suggest vestiges of migration, trade, and colonialism, as well as more recent periods of isolation, marginalization, and occupation.

This study investigated the relationship between ¹⁸O and ²H isotopes in samples of Mexican hair and drinking water. The purpose of this study was twofold: to quantify the relationship between isotopes in Mexican hair and tap water, in order to understand the impact of water stress and differing socioeconomic status on accurate predictions of drinking water; and to determine whether currently existing semimechanistic models can accurately represent the relationship between hair and tap water. This study used a subset of paired samples of human hair (n = 62) and tap water (n = 76). Isotope values in tap water ranged from –11.4‰ to –4.3‰ and –79.1‰ to –22.5‰, and in hair from +9.5‰ to +16.1‰ and –90.8‰ to –53.7‰, for δ¹⁸O and δ²H, respectively. The most depleted δ¹⁸O and δ²H hair values came from individuals in the state of Morelos. For modern Mexican populations, positive correlations between isotopes in hair and water were not significant, with correlation coefficients r = 0.61 (p = 0.05) and r = 0.60 (p = 0.06) for ¹⁸O and ²H, respectively. Error-in-variables regression yielded linear fits that were somewhat better for ²H relative to ¹⁸O: δ¹⁸O_h = 0.183 [±0.132] δ¹⁸O_tw + 15.7 [±0.9]‰ (r² = 0.23); δ²H_h = 0.181 [±0.076] δ²H_tw – 64.0 [±3.0]‰ (r² = 0.34). In short, data from this Mexican population did not exhibit the strong relationships between isotope values of ¹⁸O and ²H in tap water and hair that have been characteristic of other populations studied to date. Given the economic stratification of this region and the poor correlation between hair and water samples, the authors considered the possibility that l, the fraction of the diet derived from local sources, and f_s, the fraction of nonexchangeable H in keratin that was fixed in vivo, are local rather than global parameters for this population. The authors estimated different values of l and f_s for each location. Given the anticipated importance of the nonlocal dietary contribution, they treated the isotopic content of nonlocal food and the offset parameters for predicting isotopes in locally derived food as tuning parameters and compared the results with parameters based on the American supermarket diet. They found that, although O and H isotopes in water and hair maintained similar geographic distributions, O and H isotopes in tap water explained only a small part of the variation observed in hair samples. Compared to the standard American supermarket diet, the Mexican estimates for nonlocal diet and local diet offsets predicted regional distributions of l and f_s that cleanly segregated urban areas from rural towns.

Reliable age-at-death estimates from the adult skeleton are of fundamental importance in forensic anthropology, because it contributes to the identity parameters used in a medicolegal death investigation. However, reliable estimates are difficult because many traditional aging methods depend on a set of population-specific criteria derived from individuals of European and African descent. The absence of information on the potential differences in the aging patterns of underrepresented, especially Latinx, populations may hinder our efforts to produce useful age-at-death estimates. In response to these concerns, this study explores the utility of currently available aging techniques and whether population-specific aging methods among Latinx groups are needed. The authors obtained data from two skeletal collections representing modern individuals of Mexican and Puerto Rican origin. They examined five newly developed computational shape-based techniques using 3D laser scans of the pubic symphysis and one traditional bone-to-phase technique. A validation test of all computational and traditional methods was implemented, and new population-specific equations using the computational algorithms were generated and tested against a subsample. Results suggest that traditional and computational aging techniques applied to the pubic symphysis perform best with individuals within 35–45 years of age. Levels of bias and inaccuracy increase as chronological age increases, with overestimation of individuals younger than 35 years and underestimation of individuals older than 45 years. New regression models provided error rates comparable to, and in some occasions outperformed, the original computational models developed on white American males, but age estimates did not significantly improve. This study shows that population-specific models do not necessarily improve age estimates in Latinx samples. Results do suggest that computational methods can ultimately outperform the Suchey-Brooks method and provide improved objectivity when estimating age at death in Latinx samples.

Modern computational resources make available a rich tool kit of statistical methods that can be applied to forensic questions. This tool kit is built on the foundation of statistical developments dating back to the 19th century. To fully and effectively exploit these developments, both the makers and users of software must be keenly aware of the quality, that is, the accuracy and precision, of the data being modeled or analyzed, and end users must be sufficiently familiar with the underlying theory to understand the process and results of any analysis or software they use. This is especially important for medicolegal personnel who might be called upon to testify in a court of law and be subject to cross-examination. With respect to the development of computational tools, it is increasingly important that they be made available as open-source code to avoid the pitfalls of commercial software support and the potential dependence of end users on orphaned software.