Leslea J Hlusko

Centro de Investigación sobre la Evolución Humana | CENIEH · Paleobiology of Hominins

Objectives: Here, we describe the morphology and geologic context of OH 89, a ~1.8-million-year-old partial hominid clavicle from Olduvai Gorge, Tanzania. We compare the morphology and clavicular curvature of OH 89 to modern humans, extant apes, and a sample of other hominid fossil clavicles. Materials and Methods: Comparative samples include 59 mo...

Did Beringian environments represent an ecological barrier to humans until <15,000 years ago or was access to the Americas controlled by the spatial-temporal distribution of North American ice sheets? Beringian environments varied with respect to climate and biota, especially in the two major areas of exposed continental shelf. The East Siberian Ar...

The aim of this study is to introduce and systematically assess a new assemblage of colobine fossils (n = 360) recovered from Late Pleistocene (ca. 100,000 years ago) sediments in the Middle Awash research area, Afar Rift, Ethiopia. We describe the colobine fossils relative to extant colobine taxa and Middle Pleistocene fossil samples from “Andalee...

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 subs...

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. We describe the two assemblages and compare them to extant cercopithecin species and the s...

Evidence of how gestational parameters evolved is essential to understanding this fundamental stage of human life. Until now, these data seemed elusive given the skeletal bias of the fossil record. We demonstrate that dentition provides a window into the life of neonates. Teeth begin to form in utero and are intimately associated with gestational d...

Advances in genetics and developmental biology are revealing the relationship between genotype and dental phenotype (G:P), providing new approaches for how paleontologists assess dental variation in the fossil record. Our aim was to understand how the method of trait definition influences the ability to reconstruct phylogenetic relationships and ev...

Synopsis: The ectodysplasin pathway has been a target of evolution repeatedly. Genetic variation in the key genes of this pathway (EDA, EDAR, and EDARADD) results in a rich source of pleiotropic effects across ectodermally-derived structures, including teeth, hair, sweat glands, and mammary glands. In addition, a non-canonical Wnt pathway has a ve...

Previous genotype:phenotype mapping of the mouse and primate dentition revealed the presence of pre- and post-canine modules in mice and anthropoid primates, as well as molar and premolar submodules in anthropoid primates. We estimated phenotypic correlation matrices for species that sample broadly across Mammalia to test the hypothesis that these...

Gene variants that influence human biology today reflect thousands of years of evolution. Genetic effects on infant health are a major point of selective pressure, given that childhood survival is essential to evolutionary success. Knowledge of this evolutionary history can have implications for pediatric research. Conclusion: An episode of human a...

A widely accepted model for the peopling of the Americas postulates a source population in the Northeast Asian maritime region, which includes northern Japan. The model is based on similarities in stone artifacts (stemmed points) found in North American sites dating as early as 15,000 years ago and those of comparable age in Japan and neighboring r...

The ectodysplasin receptor (EDAR) is a tumor necrosis factor receptor (TNF) superfamily member. A substitution in an exon of EDAR at position 370 (EDARV370A) creates a gain of function mutant present at high frequencies in Asian and Indigenous American populations but absent in others. Its frequency is intermediate in populations of Mexican ancestr...

Ancient DNA analyses have shown that interbreeding between hominin taxa occurred multiple times. Although admixture is often reflected in skeletal phenotype, the relationship between the two remains poorly understood, hampering interpretation of the hominin fossil record. Direct study of this relationship is often impossible due to the paucity of h...

Variation in the dentition yields insight into the evolutionary history of Mammalia. However, to date, there has been limited research on the dental variation in Pteropodidae, a family of bats found throughout sub-Saharan Africa, Southeast Asia, and Oceania. Most species are large, diurnal, non-echolocating, and eat fruit or nectar. Pteropodids are...

Histological analysis of teeth can yield information on an organisms growth and development, facilitating investigations of diet, health, environment, and long-term responses to selective pressures. In the Americas, an extraordinary abundance of Late Pleistocene fossils including teeth has been preserved in petroleum seeps, constituting a major sou...

Paleontology has long relied on assumptions about the genetic and developmental influences on skeletal variation. The last few decades of developmental genetics have elucidated the genetic pathways involved in making teeth and patterning the dentition. Quantitative genetic analyses have refined this genotype:phenotype map even more, especially for...

You can watch my reading of this chapter here: https://vimeo.com/413679812

Colleagues often refer to Alan Walker as the Eric Clapton (one of the most influential musicians of the late twentieth century) of palaeoanthropology in recognition of the artistry of his science. His field discoveries filled major gaps in our knowledge of primate evolution, such as elucidating the Miocene world of Proconsul and finding the transit...

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 gene...

Several genome-wide association studies reveal that a variant of the Ectodysplasin A Receptor (EDAR) has an additive effect on human incisorshoveling, such that the presence of one or two alleles of V370A corresponds to a moderate or strong degree of shoveling. We analyzed shoveling for 5,333 individuals from 54 archaeological populations across Eu...

Objectives: Although a great deal is known about the biology of tooth development and eruption, there remains disagreement about the factors driving the evolution of dental eruption sequence. We assessed postcanine eruption sequence across a large sample of primates to test two hypotheses: (1) Dental eruption sequence is significantly correlated w...

Machine learning is a formidable tool for pattern recognition in large datasets. We developed and expanded on these methods, applying machine learning pattern recognition to a problem in paleoanthropology and evolution. For decades, paleontologists have used the chimpanzee as a model for the chimpanzee-human last common ancestor (LCA) because they...

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 dat...

The past few years of genetic research on primate quantitative trait variation have been notable in the diversity of phenotypes explored, ranging from classic skeletal measurements to behavior, through to levels of gene expression, and with observations from both captive and wild populations. These studies demonstrate the importance of captive pedi...

Significance The frequency of the human-specific EDAR V370A isoform is highly elevated in North and East Asian populations. The gene is known to have several pleiotropic effects, among which are sweat gland density and ductal branching in the mammary gland. The former has led some geneticists to argue that the near-fixation of this allele was cause...

The sequence of eruption of the second generation of teeth varies across taxa, is highly functional, and is strongly influenced by genetic effects. We assessed postcanine dental eruption sequence across artiodactyls in order to test two hypotheses: 1) dental eruption sequence is a good phylogenetic character for artiodactyls; and, 2) eruption seque...

Eight years of excavation work by the Olduvai Geochronology and Archaeology Project (OGAP) has produced a rich vertebrate fauna from several sites within Bed II, Olduvai Gorge, Tanzania. Study of these as well as recently re-organized collections from Mary Leakey's 1972 HWK EE excavations here provides a synthetic view of the faunal community of Ol...

Objective: Herein we introduce a newly recovered partial calvaria, OH 83, from the upper Ndutu Beds of Olduvai Gorge, Tanzania. We present the geological context of its discovery and a comparative analysis of its morphology, placing OH 83 within the context of our current understanding of the origins and evolution of Homo sapiens. Materials and m...

The rich paleontological record of South Africa is central in our understanding of Plio-Pleistocene mammalian evolution due in large part to the number of crania recovered. Because of the difficulty of chronometric control in many of the cave systems from which these fossils derive, extinct Old World Monkeys (OWMs) are often employed as biochronolo...

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 nonhum...

Significance Experimental research on mice has yielded tremendous biological insight. However, the ∼140 million y of evolution that separate mice from humans pose a hurdle to direct application of this knowledge to humans. We report here that considerable progress for identifying genetically patterned skeletal phenotypes beyond the mouse model is p...

Paleontologists typically reconstruct past behavior by assuming that function follows form. But there can be more than one function for a given form, and different forms can serve the same function. Deconstructing these relationships can be complicated. Here, we use an example from human evolution—markedly different tooth morphologies in early homi...

While the identification of conserved processes across multiple taxa leads to an understanding of fundamental developmental mechanisms, the ways in which different animals fail to conform to common developmental processes can elucidate how evolution modifies development to result in the vast array of morphologies seen today - the developmental mech...

Objective Our aim was to recover new evidence of the evolution of the hominid lineage.Methods We undertook paleontological fieldwork at Olduvai Gorge, Tanzania, in one of the richest paleoanthropological sites in the world, documenting the evolution of our lineage and its environmental contexts over the last 2 million years.ResultsDuring field work...

A well-known tenet of murine tooth development is that BMP4 and FGF8 antagonistically initiate odontogenesis, but whether this tenet is conserved across amniotes is largely unexplored. Moreover, changes in BMP4-signaling have previously been implicated in evolutionary tooth loss in Aves. Here we demonstrate that Bmp4, Msx1, and Msx2 expression is l...

Variation in the shape of teeth provides an immense amount of information about the evolutionary history and adaptive strategy of a mammalian lineage. Here, we explore variation in the expression of a purported molar lingual remnant (the interconulus) across the Old World Monkeys (Primates: Cercopithecidae) with the aim of elucidating a component o...

Unperturbed fetal development is essential for future health of an individual. Previous studies have linked diseases of aging to harmful alterations that happen during fetal development. Given the significant long-term impact that intrauterine environment has on an individual's life, it was hypothesized that maternal stress during pregnancy will ha...

Here we describe dental remains from a Neanderthal fossil assemblage from Moula-Guercy, France. Our report demonstrates that the Moula-Guercy hominid remains contribute important morphological, developmental, and behavioral data to understanding Neanderthal evolutionary history. We include gross comparative morphological descriptions and enamel sur...

In the late twentieth century, a shift in morphological analyses emerged. Rather than focusing on linear measurements and qualitative descriptions of shape, it became possible to describe quantitatively and compare morphology (Adams et al. 2004). While the dilemma of oversimplifying linear measurements had long been recognized, it was not until a n...

The study of modularity can provide a foundation for integrating development into studies of phenotypic evolution. The dentition is an ideal phenotype for this as it is developmentally relatively simple, adaptively highly significant, and evolutionarily tractable through the fossil record. Here, we use phenotypic variation in the dentition to test...

40Ar/39Ar dating of volcanic alkali feldspars provides critical age constraints on many geological phenomena. A key assumption is that alkali feldspar phenocrysts in magmas contain no initial radiogenic 40Ar (40Ar∗), and begin to accumulate 40Ar∗ only after eruption. This assumption is shown to fail dramatically in the case of a phonolitic lava fro...

The concept of modularity provides a useful tool for exploring the relationship between genotype and phenotype. Here, we use quantitative genetics to identify modularity within the mammalian dentition, connecting the genetics of organogenesis to the genetics of population-level variation for a phenotype well represented in the fossil record. We est...

To understand developmental mechanisms of evolutionary change, we must first know how different morphologies form. The vast majority of our knowledge on the developmental genetics of tooth formation derives from studies in mice, which have relatively derived mammalian dentitions. The marsupial Monodelphis domestica has a more plesiomorphic heterodo...

Thousands of vertebrate specimens were systematically collected from the stratigraphic interval containing Ardipithecus ramidus. The carcasses of larger mammals were heavily ravaged by carnivores. Nearly 10,000 small-mammal remains appear to be derived primarily from decomposed owl pellets. The rich avifauna includes at least 29 species, mostly non...

The dental research implications of the physiological, immunological, and morphological similarities between baboons and humans have long been recognized (Virgadamo et al., 1972; Aufdemorte et al., 1993). Applied dentistry has widely employed the baboon as a model upon which to develop procedures and techniques and to test the material biocompatibi...

Variation in the mammalian dentition is highly informative of adaptations and evolutionary relationships, and consequently has been the focus of considerable research. Much of the current research exploring the genetic underpinnings of dental variation can trace its roots to Olson and Miller's 1958 book Morphological Integration. These authors expl...

Many studies of primate diversity and evolution rely on dental morphology for insight into diet, behavior, and phylogenetic relationships. Consequently, variation in molar cusp size has increasingly become a phenotype of interest. In 2007 we published a quantitative genetic analysis of mandibular molar cusp size variation in baboons. Those results...

Through previous works in the early 1930s by C. Arambourg and in the 1960–1970s by the International Omo Research Expedition (IORE) initiated by F. C. Howell, the Omo Group deposits of the Lower Omo Valley provided decisive data on Plio-Pleistocene environmental change and hominid evolution in eastern Africa. Y. Coppens directed the IORE French com...

Bringing together a variety of accomplished dental researchers, this book covers a range of topics germane to the study of human and other primate teeth. The chapters encompass work on individuals to samples, ranging from prehistoric to modern times. The focus throughout the book is the methodology required for the study of modern dental anthropolo...

Primate evolutionary studies rely significantly on dental variation given the large role that teeth play in how an organism interacts with its environment (animal and plant) and conspecifics. Variation in cusp size has been shown to vary among primate taxa, although most studies to date focused on extant and extinct hominoids. Here we test the assu...

Phenotypic variation is critical to many aspects of biological research. Use of a captive population to address questions concerning the genetics and evolution of dental variation raises the question of how the pattern of phenotypic variation under study compares with that in a wild population of the same species. Differences in the pattern of vari...

We present preliminary results from quantitative genetic analyses of tooth size variation in two outbred pedigreed populations, baboons and mice. These analyses were designed to test the dental field theory as proposed by Butler (1939), that there are three fields within the dentition: incisor, canine, and molar. Specifically we estimated the genet...