Skeletal variation and evolution
My research has two main and complementary parts: investigating (1) how skeletal phenotypes are patterned in extant animals where large and complete samples are available, and (2) how skeletal phenotypes evolve, as evinced by the fossil record.
Early modern HUMAN EVOLUTION
My dissertation research was centered on the description of Late Pleistocene human postcranial fossils, including a partial skeleton, from the Middle Awash study area in Ethiopia. This work included the initial comparative description, placing these fossils in the context of the Pleistocene fossil record and recent modern human populations. My research was generously funded by the National Science Foundation (see Award Abstract here), the Leakey Foundation (see Grantee Spotlight here), the Portuguese Studies Program at UC Berkeley, and the Institute of International Studies at UC Berkeley (see Project Description here). Publication of the chronostratigraphic framework for these fossils was led by my collaborator Elizabeth Niespolo (PNAS, 2021). The results of my dissertation and ongoing work are being prepared for publication, in coordination with the associated behavioral and ecological evidence. The next phases of this research will turn to hominid fossils from one of the most elusive time periods of human evolution: the Middle Pleistocene.
FIELD REsearch in THE middle awash, Ethiopia
I’m a paleontologist on the Middle Awash Research Project, focusing on fossil hominids and monkeys. I’ve been out for two field seasons with the project (2015, 2017) and am involved in ongoing work at the National Museum of Ethiopia. Ongoing projects include the curation, taxonomic description, and detailed comparative study of early modern humans and cercopithecid monkeys. Along with collaborators Cat Taylor, Tesla Monson, Ryan Yohler, and Leslea Hlusko (AKA #TeamMonkey), I’ve been working on describing nearly a thousand monkey individuals from later Pleistocene sediments, sampling three lineages (Colobus, Papio, and cf. Chlorocebus). Our work has culminated in three papers, recently published at the American Journal of Biological Anthropology (Brasil et al., Colobus; Brasil et al., Papio; and Taylor et al., cf. Chlorocebus). Our next big phase of this project will look to even more monkeys in older (Middle Pleistocene) sediments.
MECHANISMS PATTERNING MAMMALIAN DENTAL VARIATION
I’m collaborating on an ongoing set of projects that grew out of a really fun and exciting initial project (/adventure…) led by Leslea Hlusko. By leveraging very large and diverse extant and fossil datasets and pulling in quantitative genetic analyses, we identified two dental phenotypes that reflect the output of genetic patterning mechanisms (PNAS, 2016). My former labmate and collaborator Tesla Monson led an international team in examining the relationship between these two phenotypes with diet and phylogeny in a large sample of boreoeutherian mammals (Ecology and Evolution, 2019). I then led our team in exploring how these phenotypes pattern across the human clade, which has implications for the selection of phenotypes in taxonomic assessments and phylogenetic analyses (The Science of Nature, 2020). More recently, we assessed variation and evolution of these dental phenotypes in the maxillary dentition of cercopithecid monkeys. We combined quantitative genetic analyses with ancestral state reconstruction to find that observed phenotypes in the cercopithecid fossil record exceed the variation among predicted ancestral values, underscoring the value and necessity of fossil evidence for elucidating evolutionary patterns (Biology, 2022). Our most recent work leverages these dental phenotypes to study prenatal growth rates in the hominid fossil record, opening a new window onto the evolution of human pregnancy (PNAS, 2022).
AFRICAN CERCOPITHECID MONKEY EVOLUTION
In parallel to my more human-focused work and my work with the Middle Awash Research Project, I’ve been involved in an ongoing set of projects investigating cercopithecid monkey morphology. This has included exploring craniofacial variation in southern African monkeys and reassessing taxonomic categories, and taking a more explicitly hypothesis-based approach to the taxonomy of genus Parapapio (in prep). You can read about some of this work (and ensuing adventures) here in a blog post I wrote with Tesla Monson for the University of California Museum of Paleontology.
MODERN HUMAN SKELETAL VARIATION
The newest branch of my research program is focused on skeletal variation in recent modern humans, exploring patterns of covariation in the postcranial skeleton. I’m currently working on a project assessing population-based variation in shaft-to-end proportions of human limb bones. Other projects are in development, so please stay tuned!