Considerable research has shown that modern human pelvic dimensions, especially of the birth canal, are sexually dimorphic. Studies also suggest that females with younger ages-at-death have narrower canal dimensions than those who die at older ages, possibly due to continued independent growth of the pubis. A recent examination of this pattern argued that it is unlikely that these differences relate to mortality, but the source of the difference in pelvic dimensions with age remains unresolved. We use pelvic dimensions to assess differences in magnitudes of morphological integration between adult females and males across agesat-death. We first ascertain whether the sexes have different strengths of integration, and then assess if differences in magnitudes of integration are associated with age-at-death. Pelvic dimensions of all groups were moderately integrated. Females and males have similar magnitudes of integration, and there is no change in the strength of integration with age. Examining individual regions of the pelvis indicates that the ilium, pubis, and pelvic inlet and outlet have stronger integration than the overall pelvis. This was particularly true of the pelvic outlet, which demonstrated the strongest integration. Our findings suggest that regions of the pelvis are more strongly integrated internally, and less integrated with each other, which would allow for proportional growth among regions of the pelvis with age that do not affect its overall integration. No single region of the pelvis appears to be motivating the difference in pelvic dimensions between age groups. We further consider the implications of these findings on evolutionary constraints. Anat Rec, 300:666-674, 2017. V C 2017 Wiley Periodicals, Inc.

Anatomical data are often used to infer genetic similarities within and between human populations. Intergroup similarities may result from multiple processes, including common ancestry, shared environment during ontogeny, or gene flow. In many cases, researchers have used pattern‐based comparisons, such as least squares distances between groups, to suggest these processes, even though pattern‐based methods inadequately measure such evolutionary and developmental processes. Methods that utilize the genetic covariance matrix (or phenotypic covariance matrix as a proxy) to understand the apportionment of variance are better suited to the analysis of how evolutionary processes shaped morphology.A goal for researchers is to apply analytical methods that better measure processes to reevaluate studies that used pattern‐based approaches. Because these studies were often conducted using skeletons that are no longer available, an additional challenge is that only archival data are available. In this study, we demonstrate this research approach to validate its effectiveness and explore its limitations.We use fifteen craniometric distances recorded by Dr. Richard Jantz in the 1970s from ten Arikara village burial sites in South Dakota (c. 1550–1832 AD). Jantz used pattern‐based approaches to suggest increased gene flow over time with the Mandan and Europeans. The conclusion from this study was that gene flow increased as pressure from colonizing groups forced intermarriage between previously discrete groups. Our study tests this conclusion using a quantitative genetic model developed by Relethford & Blangero. Their method uses population variance based on metric traits to model the amount of variance that should be expected in each group versus what is actually observed.Our results show that the evidence for gene flow varied more between sites than over time, and that there is no clear temporal trend. For example, two early sites (early Mobridge and Rygh, c. 1550–1600) have contrasting evidence for gene flow. Rygh has less‐than‐expected variance, an indicator of a lack of gene flow, while higher‐than‐expected variance in the earliest component of Mobridge suggests possible increased gene flow that is not present in the site's later component (c. 1625–1750). Two later period sites, Larson and Cheyenne River, also show contrasting evidence for gene flow. The most recent site, Leavenworth (dating to the early 1800s) has greater than expected variance, which is congruent with historical documentation that indicates the occurrence of gene flow. We conclude that the patterns of gene flow during the period of European colonization and population decimation in the Northern Plains is more nuanced than previous methods were able to detect.This project provides new insight into questions that have been of interest to researchers for decades by using a process‐based approach instead of a pattern‐based one. Moreover, it highlights the importance of archival data in pursuing research questions, as (with a few exceptions) archival data are often an underused resource. With newer methods these data still provide further understanding of evolutionary processes and human variation.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

The use of metric data from skeletal remains to assess models of evolutionary processes is a well‐established substitute for genomic data. However, it has been suggested in previous research that certain osteological elements retain population history signatures better than others because they are likely less subject to natural selection. This study examines the potential for differences in gene flow models using human crania (traits shown to evolve through neutral processes) versus postcrania (traits provisionally shown to have evolved in response to selection). In this study, we sampled from four large pueblos in the American Southwest representing a short temporal period and small geographic area (Arizona, c. 1200–1400, N=267). Based on a robust archaeological record detailing changes in material culture, researchers hypothesize immigration into this region from non‐local populations. The study uses gene flow models based on variance comparison methods developed by Relethford and Blangero. Metric data were analyzed using the R statistical environment and RMET 5.0, a program based on the Relethford‐Blangero statistics. Under a quantitative genetic model, gene flow results in higher‐than‐expected variance in a population, which RMET examines. Likewise, gene flow decreases the biodistance between populations sharing genes, and so these were compared through Mahalanobis D2 distances. Cranial and postcranial dimensions generally result in different patterns of gene flow. Comparing residual phenotypic variances from the Relethford‐Blangero model, only one of the four sites presents the same pattern of gene flow between cranial and postcranial results. Biodistance analyses show that the Pueblo population that is the greatest distance remains consistent in both crania and postcrania, but which of the other three is closest changes between the two body regions. This incongruence has implications for local disparities in the variance and in the mean differences between aspects of morphology. Either the upper or lower limb elements may be driving the discrepancies, as limb bones are shown to respond dissimilarly to selection on a global scale. We conducted analyses comparing results of the upper and lower limbs. The results indicate upper limb residual variances are higher, but only the lower limb matches the patterns observed in the overall postcranial analysis. Biological distance relationships are very similar between the limbs, though the lower limb data is closer in magnitude to the overall postcranial distance. It is possible that the lower limb is driving the variance results for the postcrania, a result that provisionally reflects the evolution of femoral traits in recent humans in response to neutral processes. This has implications for how we evaluate population history using phenotypic data, particularly considering which phenotypic data to employ. Support or Funding Information This research was partially funded by the University of Tennessee Department of Anthropology through a Kneberg‐Lewis Scholarship.

This study examines morphological integration (MI) in the human pelvis with respect to sex and age. Anatomists and biological anthropologists have often cited the flair of the iliac blades, sub‐pubic angle, and breadth between the ischia among the morphologies that distinguish females and males, though the magnitude of difference between the sexes varies among groups. Despite these differences, it is assumed that patterns of MI within the human pelvis are the same between the sexes; the few studies of evolvability and integration in the pelvis to date remove effects of sexual dimorphism on the variance‐covariance matrix. In addition, the age of adult individuals is never considered a factor in quantitative genetic studies of the evolution of the pelvis, as the pelvis is thought to reach its definitive morphology with the cessation of primary growth. However, studies by Tague (1994) and Auerbach et al. (in review) show that older adult females have mediolaterally wider pelvic outlets (MLPO) and anteroposteriorly deeper pelvic inlets (APPI), while no age‐related differences in pelvic dimensions are observed among males. Though covariation within the pelvis should be similar between the sexes and among age groups within the sexes, no assessment of overall integration within the pelvis has been compared in light of these factors.In this study, 18 linear dimensions were measured from the rearticulated pelves of 327 adult human skeletons (188 females, 139 males) recovered from archaeological sites in North America dating from the last millennium. Fusion of the iliac crest was the criterion for inclusion. We aged the skeletons based on diagnostic changes in pelvic articular morphology, and placed the skeletons into two groups: “Young” (<~25 years) and “Not Young” (>~25 years). MI was measured by comparing relative eigenvalue variances between sex and age‐and‐sex groups, following Pavličev et al. (2009. Evol Biol 36:157–170), as well as by comparing mean‐scaled covariance matrices of the traits within each group. Relative eigenvalue variances have a scale of zero to one and higher values indicate more integration.Results indicate that MI differs notably between age groups within sex, but not between the sexes. Both females and males have similar relative eigenvalues (females = 0.162; males = 0.172). The slightly lower value for females may be driven by the influence of the Young female group, which has a relative eigenvalue variance of 0.139. In contrast, the Not Young female group has relative eigenvalue variance of 0.202. This is a stark difference, and indicates that younger females have less integration than older females. Examination of the covariance matrices indicates lower covariances among most traits, but especially between MLPO and APPI. This indicates that covariation of traits within the pelvis continue to change in adults, and older females have more integrated pelves. Further developmental and evolutionary implications are considered.Support or Funding InformationNational Science Foundation, BCS Grant #0962752