Kieran P. McNulty, Ph.D. - US grants

Fossil deposits on the Kenyan islands of Rusinga and Mfwangano comprise one of the richest sources of information for understanding the origin and diversification of the earliest apes. Best known for the primitive ape Proconsul and catarrhine primates Dendropithecus, Nyanzapithecus, and Limnopithecus, Rusinga/Mfwangano sites also preserve copious mammal, reptile, bird, and invertebrate fossils, as well as rarely seen fossil elements such as leaves, seeds, fruits, and insects. Thus, it becomes possible to reconstruct not just the anatomy of these primates, but also their chronological context, aspects of their feeding ecology, habitat preferences, and the broader ecological community in which they thrived. This project will undertake new research on Rusinga/Mfangano to further our knowledge of the chronology and paleoecology of stem catarrhines and hominoids. Specific objectives are to: 1) establish stratigraphic and chronological control within and among primate fossil sites on Rusinga and Mfangano; and 2) reconstruct paleoenvironmental conditions throughout the geological sequence to assess the ecological parameters in which these primates lived. Work will be carried out over three summers and include basic stratigraphic analysis, absolute and relative dating, controlled fossil collection, analyses of stable isotopes, revisions of existing faunal collections, and dental microwear analysis. The intellectual merit of this project lies in combining geological, paleontological, and paleoecological methodologies to substantially advance our knowledge of hominoid evolution and adaptation through development of high-resolution chronostratigraphic data and detailed paleoecological models for Rusinga and Mfangano catarrhine primates. This project also has considerable broader impact in promoting education and cooperation at the local level, advancing local involvement in the preservation of the fossil heritage, employing local and national Kenyan workers, educating undergraduate and graduate students, and promoting international and interdisciplinary collaborations.

New evidence from early fossil humans suggests that, in some respects, these hominins more closely resembled the earliest fossil apes than any modern ape. While such findings substantially impact our understanding of early hominin adaptive morphology, their precise implications remain unclear because the original ecological conditions in which these features evolved is poorly documented. To address this problem, this project will answer the following three research questions: What are the regional patterns of environmental change and the site-specific habitats associated with the earliest fossil apes? How does the morphology of early apes relate to the environmental contexts in which they lived? How do early ape adaptations inform our understanding of later ape and human evolution? These questions will be answered by establishing a multi-disciplinary, multi-national collaboration to initiate new paleontological field research at all of the early fossil ape localities in East Africa. For the first time, new fossil and data collection will be coordinated across nearly a dozen Kenyan sites near Kisingiri, Tinderet, West Turkana, and Buluk, and a similar number of Ugandan sites at Napak, Moroto, and Bukwa. In addition to surveys and excavation, a series of geological, ecological, and taphonomic analyses will be used to understand the age, environment, and setting of each locality. New fossils will be subjected to rigorous morphological analyses to determine their evolutionary and adaptive significance. Unlike previous studies, which have focused on individual localities, this regional approach to understanding ancient ecosystems will track environmental variations over the time and space of early ape evolution, making it possible to relate specific habitat types with primate adaptive morphology.

The origin and early diversification of the ape-human lineage represents a fundamental shift in primate body plans, and is therefore an integral resource for interpreting the later evolution of apes and humans. For decades, most researchers have studied human origins through the lens of modern ape and human characteristics, marginalizing a large and diverse body of evidence from their ancient ape predecessors. This project represents an important and substantive step toward fully integrating our knowledge of living and fossil apes and humans. Moreover, coordinating a project of this breadth - using the same methods and protocols across all of the relevant fossil sites - will allow data to be synthesized on a scale not previously possible, setting new benchmarks for conducting future field projects. This project will thus model a collaborative approach that will be more productive and beneficial to the discipline of paleoanthropology.

This project also generates substantial broader impacts. A critical component of the grant is the training of US and East Africa graduate and US undergraduate students in the discipline of paleoanthropology. The project also includes the National Museums of Kenya as a full collaborative scientific partner in the proposed research. A well-established partnership between University of Michigan, Makerere University and the National Museum (Uganda) will be fostered by this grant, helping to train staff and students in Uganda on field and analytical techniques. Finally, a digital database cataloging all the fossils and data collected from all of the localities will be made freely available after the conclusion of the project.

Many nonhuman primate species have sex differences in the size and shape of their canine and premolar teeth, but in the human lineage those differences are smaller. This project models the genetic inheritance of canine and premolar tooth size in several primate species, including a modern human sample, to examine the impact of genetic structures on the evolution of sex differences in canine size. The findings will be used to understand mechanisms of canine reduction in the human lineage and canine expansion in other primates, and contribute to our understanding of evolutionary relationships among diet, behavior, and dentition in our hominin ancestors. elective pressures related to aggression and diet are hypothesized to contribute to sex differences in primate canine teeth, and changes in these selective pressures may have led to human canine and premolar reduction. The project will support training of a female student in a STEM field, production of a large dataset that will be made public for other researchers, and outreach activities such as public lectures focused on improving public understanding of primate diversity and evolution.

Dental characteristics provide valuable evidence of genetic relatedness in primates, and tooth measurements are well-suited to classical quantitative genetic analysis, which uses pedigree data to estimate the genetic heritability of traits. This project assesses the genetic inheritance of canine and premolar dimensions in several primate species with the specific aim of elucidating the genetic mechanisms underlying sex differences in the morphology of these teeth. Previous researchers have stated that sex differences in genetic inheritance and low overlap in male and female genetic material contribute to the evolution of sex differences, but these hypotheses have not been tested in primates. This project addresses three fundamental research questions: 1) Are sex differences in canine and premolar size associated with sex differences in trait inheritance? 2) Do the same genes impact the size of the upper canine and lower premolar? 3) Do primate species with sex differences in the canine have more evolvable canines than those with no sex differences? These questions can be answered using tooth size measurements collected from primate populations with known pedigrees. Statistical models will be used to estimate the inheritance of canine and premolar size in each population. Preliminary data collection and analyses of saddle-back tamarins indicate that there are significant differences between male and female patterns of trait inheritance, but data from additional populations and species will demonstrate whether this is typical of primates broadly or a peculiarity limited to a single tamarin population.

This doctoral dissertation project examines how competition affects primate adaptive processes, testing the central hypothesis that primates respond to competition over food resources by focusing feeding on underutilized resources. Using measures of tooth shape to analyze traits, and stable isotope analysis to examine diet and canopy use, this project looks at differences between primate pairs by comparing populations that live together to populations that live separately. The study can provide new information relevant to conservation management programs to prevent further primate extinction by documenting the impacts of increased competition due to habitat loss. Data collected for this project create undergraduate internship opportunities and provide training in the protocols and procedures of conducting original research. Results from this research will be incorporated into learning modules based on the themes of primate diet and conservation. These learning modules will be utilized by a local non-profit educational programming group that provides scientific activities to elementary and middle school students.

This project asks two research questions: 1) do closely-related primate species focus their diet on a few key food items when they live together compared to the same species when they occur separately? and 2) do closely-related primate species display morphological traits and isotopic signatures that reflect focus on fewer key resources when they live together compared to the same species when they occur separately? These questions will be tested using ecometric measures to quantify tooth shape and stable isotope data to represent diet and canopy use. By combining methods to analyze tooth shape and isotopic signatures related to habitual canopy level occupation, this project will provide new perspectives on how to reconstruct dietary behaviors and resource competition.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2). This project examines the roles of time and environment in the adaptive evolution of early apes by advancing knowledge about the chronology, paleoecology, and species diversity for a set of geographically restricted fossil localities. The research design includes a series of fossil excavations to uncover new evidence of early apes and their habitats, combined with laboratory analyses designed to aid in synthesizing and interpreting these discoveries. The scientific importance of this project lies in documenting early ape adaptive diversity within specific, highly-resolved chronological and ecological contexts, with major downstream implications for interpreting the origin and diversification of later apes, including hominins. More broadly, this project expands participation in research through training opportunities targeted to underrepresented groups, enhances scientific infrastructure by digitizing invaluable but currently inaccessible field records, and increases public engagement with science through outreach activities aimed at museums and public schools.

Fossil and molecular evidence indicate that the major lineages of humans and apes diverged during the early Miocene (ca. 23-16 Ma). The diversity of ape species and adaptations during that time greatly exceeds modern variation in this group making it difficult to interpret the evolutionary sequence and ecological contexts in which the suite of features shared by living apes and humans appeared. This project is organized around the central question: Are differences among early apes tied to differences in paleoenvironments, ages, or both? To clarify these relationships, researchers pursue three specific aims: (1) establishing a rigorous chronology of early ape fossil sites; (2) generating high-resolution paleoecological reconstructions for undersampled ape localities; and (3) documenting the diversity of ape species during the early Miocene. Fossil excavations are conducted at a series of outcrops to better document ape diversity, geological contexts, and habitat parameters. The project employs radiometric and magnetostratigraphy at correlated stratigraphic sections (Aim 1); sedimentological, isotopic, and paleontological analyses (Aim 2); and comparative, morphometric, and phylogenetic analyses of new fossil ape specimens (Aim 3). Integration of these study results can enable the researchers to contextualize the timing and ecological parameters associated with the emergence of key characteristics in the ape and human lineage, and to subsequently interpret how these early Miocene primate communities contributed to the distribution of primates across broad regions.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.