Developmental genetics research on mice provides a relatively sound understanding of the genes necessary and sufficient to make mammalian teeth. However, mouse dentitions are highly derived compared with human dentitions, complicating the application of these insights to human biology. We used quantitative genetic analyses of data from living nonhuman primates and extensive osteological and paleontological collections to refine our assessment of dental phenotypes so that they better represent how the underlying genetic mechanisms actually influence anatomical variation. We identify ratios that better characterize the output of two dental genetic patterning mechanisms for primate dentitions. These two newly defined phenotypes are heritable with no measurable pleiotropic effects. When we consider how these two phenotypes vary across neontological and paleontological datasets, we find that the major Middle Miocene taxonomic shift in primate diversity is characterized by a shift in these two genetic outputs. Our results build on the mouse model by combining quantitative genetics and paleontology, and thereby elucidate how genetic mechanisms likely underlie major events in primate evolution.paleontology | quantitative genetics | primates | neontology | dental variation T he relationship between genotype and phenotype is critical to evolutionary biology, because it influences how phenotypes respond to selective pressures and evolve (1, 2). Paleontologists have long sought to incorporate the etiology of the dental phenotype to inform on questions of environmental, dietary, and adaptive change over time (3)(4)(5)(6). This research has been advanced significantly by the revolution in developmental genetics over the past few decades (7). Experimental research on mice has yielded tremendous biological insight (8). However, for human phenotypes, ranging from inflammation (9) to placentation (10), the limitations of the mouse model due to the ∼140 million years ago of evolution that have occurred since our last common ancestor ∼70 Ma (11) are starting to be recognized. Here, we demonstrate how to overcome the limitations of the mouse model's application to the primate dentition by integrating research from quantitative genetics, neontology, and paleontology. The insights gained from this transdisciplinary approach have implications for all of these seemingly disparate subdisciplines of biology.

In many sports, greater height and arm span are purportedly linked to athletic success. While variation in body proportions has been explored across an array of scientifi c disciplines, studies focusing on humans of tall stature outside of clinical cases are limited. We investigated body size proportions in a sample of elite athletes, employing data on recruits for the National Basketball Association (NBA, n=2,990), mixed martial arts (MMA) fi ghters (mixedsex, n=1,284), as well as a control sample of healthy young adults who are not professional athletes, represented here by male (n=4,082) and female (n=1,986) recruits for the United States Army, to test two hypotheses: 1) There is a signifi cant diff erence in arm span to height ratios between elite professional athletes and the control population, and 2) There is a signifi cant relationship between arm span to height ratio and athletic success within the NBA and MMA. We fi nd that NBA players are signifi cantly taller, with absolutely and relatively wider arm spans than MMA fi ghters and the control population. Additionally, we fi nd that basketball players are signifi cantly more likely to be drafted earlier in the NBA, and MMA fi ghters are signifi cantly more likely to have a better loss to win ratio, if their arm span to height ratio falls above the regression line. However, we note that arm span and height, as well as athletic success, are impacted by a myriad of factors, and some of the most successful professional athletes do not have particularly long arms relative to their height.

Objectives: The goals of this study were to describe and interpret two new fossil assemblages of cercopithecin monkeys (n = 328), one from the Faro Daba beds (ca. 100,000 years) and the other one from the Chai Baro beds (>158,000 years old), in the Afar Rift of Ethiopia. Materials and Methods:We describe the two assemblages and compare them to extant cercopithecin species and the smaller fossil assemblage from Asbole, Ethiopia (ca. 600 ka). We use a population-based approach to the taxonomy given the unusually large number of specimens. Craniodental and postcranial anatomy are presented.Evidence of locomotor habitus is described and evaluated in a framework of hybridization and postcranial plasticity. Results:We attribute all cercopithecin specimens from both beds to cf. Chlorocebus and conclude that the Faro Daba and Chai Baro assemblages likely sample single species at each time horizon. Subtle differences between the two assemblages, mostly in postcranial morphology, are insufficient to justify separation at the species level.Discussion: The large sample sizes and unique preservational aspects of these two assemblages open a new window into the recent evolution of guenons. Our data indicate that these fossil populations may be ancestral to the cercopithecins currently living in the Afar region of Ethiopia.

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The dentition is an extremely important organ in mammals with variation in timing and sequence of eruption, crown morphology, and tooth size enabling a range of behavioral, dietary, and functional adaptations across the class. Within this suite of variable mammalian dental phenotypes, relative sizes of teeth reflect variation in the underlying genetic and developmental mechanisms. Two ratios of postcanine tooth lengths capture the relative size of premolars to molars (premolar–molar module, PMM), and among the three molars (molar module component, MMC), and are known to be heritable, independent of body size, and to vary significantly across primates. Here, we explore how these dental traits vary across mammals more broadly, focusing on terrestrial taxa in the clade of Boreoeutheria (Euarchontoglires and Laurasiatheria). We measured the postcanine teeth of N = 1,523 boreoeutherian mammals spanning six orders, 14 families, 36 genera, and 49 species to test hypotheses about associations between dental proportions and phylogenetic relatedness, diet, and life history in mammals. Boreoeutherian postcanine dental proportions sampled in this study carry conserved phylogenetic signal and are not associated with variation in diet. The incorporation of paleontological data provides further evidence that dental proportions may be slower to change than is dietary specialization. These results have implications for our understanding of dental variation and dietary adaptation in mammals.

Objectives: The aim of this study is to assess a new assemblage of papionin fossils (n = 143) recovered from later Pleistocene sediments in the Middle Awash study area in the Afar Rift of Ethiopia. Materials and Methods:We collected metric and qualitative data to compare the craniodental and postcranial anatomy of the papionin fossils with subspecies of modern Papio hamadryas and with Plio-Pleistocene African papionins. We also estimated sex and ontogenetic age. Results:The new fossils fit well within the range of morphological variation observed for extant P. hamadryas, overlapping most closely in dental size and proportions with the P. h. cynocephalus individuals in our extant samples, and well within the ranges of P. h. anubis and P. h. hamadryas. The considerable overlap in craniodental anatomy with multiple subspecies precludes subspecific diagnosis.We therefore referred 143 individuals to P. hamadryas ssp. The majority of the individuals assessed for ontogenetic age fell into middle-and old-adult age categories based on the degree of dental wear. Males (26%) were better represented than females (12%) among individuals preserving the canine-premolar honing complex.Discussion: These new near-modern P. hamadryas fossils provide a window into population-level variation in the later Pleistocene. Our findings echo previous suggestions from genomic studies that the papionin family tree may have included a ghost population and provide a basis for future testing of hypotheses regarding hybridization in the recent evolutionary history of this taxon.

The Halibee member of the Upper Dawaitoli Formation of Ethiopia’s Middle Awash study area features a wealth of Middle and Later Stone Age (MSA and LSA) paleoanthropological resources in a succession of Pleistocene sediments. We introduce these artifacts and fossils, and determine their chronostratigraphic placement via a combination of established radioisotopic methods and a recently developed dating method applied to ostrich eggshell (OES). We apply the recently developed 230Th/U burial dating of OES to bridge the temporal gap between radiocarbon (14C) and 40Ar/39Ar ages for the MSA and provide 14C ages to constrain the younger LSA archaeology and fauna to ∼24 to 21.4 ka. Paired 14C and 230Th/U burial ages of OES agree at ∼31 ka for an older LSA locality, validating the newer method, and in turn supporting its application to stratigraphically underlying MSA occurrences previously constrained only by a maximum 40Ar/39Ar age. Associated fauna, flora, and Homo sapiens fossils are thereby now fixed between 106 ± 20 ka and 96.4 ± 1.6 ka (all errors 2σ). Additional 40Ar/39 results on an underlying tuff refine its age to 158.1 ± 11.0 ka, providing a more precise minimum age for MSA lithic artifacts, fauna, and H. sapiens fossils recovered ∼9 m below it. These results demonstrate how chronological control can be obtained in tectonically active and stratigraphically complex settings to precisely calibrate crucial evidence of technological, environmental, and evolutionary changes during the African Middle and Late Pleistocene.

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