On the misidentification of species: sampling error in primates and other mammals using geometric morphometrics in more than 4,000 individuals

An accurate classification is the basis for research in biology. Morphometrics and morphospecies play an important role in modern taxonomy, with geometric morphometrics increasingly applied as a favourite analytical tool. Yet, really large samples are seldom available for modern species and even less common in palaeontology, where morphospecies are often identified, described and compared using just one or a very few specimens. The impact of sampling error and how large a sample must be to mitigate the inaccuracy are important questions for morphometrics and taxonomy. Using more than 4000 crania of adult mammals and taxa representing each of the four placental superorders, we assess the impacts of sampling error on estimates of species means, variances and covariances in Procrustes shape data using resampling experiments. In each group of closely related species (mostly congeneric), we found that a species can be identified fairly accurately even when means are based on relatively small samples, although errors are frequent with fewer specimens and primates more prone to inaccuracies. A precise reconstruction of similarity relationships, in contrast, sometimes requires very large samples (> 100), but this varies widely depending on the study group. Medium-sized samples are necessary to accurately estimate standard errors of mean shapes or intraspecific variance covariance structure, but in this case minimum sample sizes are broadly similar across all groups (≈ 20-50 individuals). Overall, thus, the minimum sample sized required for a study varies across taxa and depends on what is being assessed, but about 25-40 specimens (for each sex, if a species is sexually dimorphic) may be on average an adequate and attainable minimum sample size for estimating the most commonly used shape parameters. As expected, the best predictor of the effects of sampling error is the ratio of between- to within-species variation: the larger the ratio, the smaller the sample size needed to obtain the same level of accuracy. Even though ours is the largest study to date of the uncertainties in estimates of means, variances and covariances in geometric morphometrics, and despite its generally high congruence with previous analyses, we feel it would be premature to generalize. Clearly, there is no a priori answer for what minimum sample size is required for a particular study and no universal recipe to control for sampling error. Exploratory analyses using resampling experiments are thus desirable, easy to perform and yield powerful preliminary clues about the effect of sampling on parameter estimates in comparative studies of morphospecies, and in a variety of other morphometric applications in biology and medicine. Morphospecies descriptions are indeed a small piece of provisional evidence in a much more complex evolutionary puzzle. However, they are crucial in palaeontology, and provide important complimentary evidence in modern integrative taxonomy. Thus, if taxonomy provides the bricks for accurate research in biology, understanding the robustness of these bricks is the first fundamental step to build scientific knowledge on sound, stable and long-lasting foundations

Pig domestication and human-mediated dispersal in western eurasia revealed through ancient DNA and geometric morphometrics

Zooarcheological evidence suggests that pigs were domesticated in Southwest Asia ∼8,500 BC. They then spread across the Middle and Near East and westward into Europe alongside early agriculturalists. European pigs were either domesticated independently or more likely appeared so as a result of admixture between introduced pigs and European wild boar. As a result, European wild boar mtDNA lineages replaced Near Eastern/Anatolian mtDNA signatures in Europe and subsequently replaced indigenous domestic pig lineages in Anatolia. The specific details of these processes, however, remain unknown. To address questions related to early pig domestication, dispersal, and turnover in the Near East, we analyzed ancient mitochondrial DNA and dental geometric morphometric variation in 393 ancient pig specimens representing 48 archeological sites (from the Pre-Pottery Neolithic to the Medieval period) from Armenia, Cyprus, Georgia, Iran, Syria, and Turkey. Our results reveal the first genetic signatures of early domestic pigs in the Near Eastern Neolithic core zone. We also demonstrate that these early pigs differed genetically from those in western Anatolia that were introduced to Europe during the Neolithic expansion. In addition, we present a significantly more refined chronology for the introduction of European domestic pigs into Asia Minor that took place during the Bronze Age, at least 900 years earlier than previously detected. By the 5th century AD, European signatures completely replaced the endemic lineages possibly coinciding with the widespread demographic and societal changes that occurred during the Anatolian Bronze and Iron Ages

Unravelling the complexity of domestication:A case study using morphometrics and ancient DNA analyses of archaeological pigs from Romania

Funding statement. This work was supported by the Natural Environment Research Council (NE/F003382/1) and the Leverhulme Trust (F/00 128/AX) Acknowledgements. Archaeozoological analyses conducted by A. Ba˘la˘s¸escu were supported by three grants from the Romanian National Authority for Scientific Research, CNCS UEFISCDI (PN-II-RU-TE-20113-0146, PN-II-ID-PCE-2011-3-0982 and PN-IIID-PCE-2011-3-1015). We thank the archeologists Ca˘ta˘lin Bem, Alexandru Dragoman, Valentin Dumitras¸cu, Laura Dietrich, Raluca Koga˘lniceanu, Cristian Micu, Sta˘nica Pandrea, Valentin Parnic, George Trohani, Valentina Voinea for the material they generously provided. We thank the many institutions and individuals that provided sample material and access to collections, especially the curators of the Museum fu¨r Naturkunde, Berlin; Muse´um National d’Histoire Naturelle, Paris; Muse´um d’Histoire Naturelle, Gene`ve; Museum fu¨r Haustierkunde, Halle; National Museum of Natural History, Washington; The Field Museum, Chicago and The American Museum of Natural History, New York; The Naturhistorisches Museum, BernPeer reviewedPublisher PD

Moving peoples, changing diets: Isotopic differences highlight migration and subsistence changes in the Upper Mun River Valley, Thailand

The dramatic growth of dietary isotope studies in archaeological literature attests to the significant potential this technique has for shedding light on past societies. Human diet reflects complex, inter-linked factors such as status, cultural preferences or environmental constraints on food production. In this study dietary isotope analysis is used to examine the human skeletal remains from Ban Non Wat, northeast Thailand. The study aims to use isotopic data to give insight into patterns of migration and subsistence strategy during prehistory. Ban Non Wat is the most comprehensively excavated site in the Upper Mun River Valley (UMRV), and understanding of prehistoric society in this area is crucial to answering questions of how social complexity arose in the region. Carbon isotope analysis has highlighted migrant individuals invisible to strontium isotope analysis and shown links between unusual burial practice and differences in diet. Results also indicate that diet changed substantially through time, with more reliance on rice in the Bronze Age, correlated with an increase in social differentiation. There is a move away from reliance on rice agriculture in the Iron Age, a time when oxygen isotopes show that environmental conditions were becoming drier, possibly resulting in rice agriculture becoming less viable