NSF Funding to Study Circumorbital Morphology

Countless revisions later…it’s official! Our NSF grant has been funded!

This is a collaboration between the Primate Evolution Lab and new incoming assistant professor Dr. Marianne Brasil. We will be 3D scanning hundreds of primate skulls, and the grant offers paid positions for one postdoctoral scholar, one graduate student, and several undergraduates. We will also be hosting a public symposium on the evolution of vision (Integrative Human Evolution Symposium, IHES 2025). We can’t wait to get started on this new project!


Investigating variation in the primate skeleton advances understanding of the evolution of modern human biology. The skull is a particularly informative area of the body as it contains most of the primary sensory organs, the mouth, and the brain. Likewise, some of the most distinctive changes in human evolution, including increased brain size, reduced jaw length, and a reduced brow ridge, occurred in the skull. Hypotheses about brain size, climate, diet, social structure, and even communication, have been proposed to explain these evolutionary changes, but how and why they happened persist as key questions in human evolutionary studies. This study focuses on the brow ridge and circumorbital region of the face, which is linked to both the brain and vision. The dataset built by this project contributes significantly to evolutionary studies by providing the most detailed picture of extant primate cranial variation to date and making these data openly available through online digital repositories. The project supports early career researchers who are underrepresented minority scientists at a U.S. primarily undergraduate institution and creates opportunities for research and mentorship of students. Novel curricular frameworks developed through this project integrate evolutionary research into the classroom, providing active learning opportunities and training relevant for health sciences careers. These activities, combined with the mentorship and training of U.S. undergraduate researchers, a Masters student, and a postdoctoral scholar, directly contribute to the advancement of science education and the growth of a diverse scientific workforce.

This study pairs 3D morphometrics with phylogenetic comparative methods to test evolutionary hypotheses about the role of circumorbital morphology in shaping human cranial evolution. The project leverages 3D surface scans of the cranium for n=1700 extant haplorrhines and n=54 fossil hominids. These data are used to address three major aims: 1) characterize circumorbital morphology in hominids and other primates, 2) quantify levels of integration between circumorbital morphology and other skeletal structures of the cranium, and 3) assess the roles of body size and sex in shaping primate circumorbital morphology. By building on foundational morphometric studies in primates with functionally-informed hypotheses and new phylogenetic and evolvability methods, this project has the potential to transform theoretical frameworks and practical approaches to studying hominid cranial evolution.

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.

Teeth and the evolution of human pregnancy

Out this month in PNAS is our new paper on teeth, prenatal growth rates, and the evolution of human-like pregnancy in later Homo

Significance: Humans are characterized by having very large brains relative to body size. Because gestation is critically linked to brain size, pregnancy is an important but elusive aspect of hominid evolution. We developed two methods for reconstructing prenatal growth during this earliest phase of life history using brain size and dental morphology. Our results indicate a significant increase in prenatal growth rates (PGRs) throughout the terminal Miocene and Plio-Pleistocene with the evolution of human-like PGRs in later Homo, less than 1 million years ago. These results align with fossilized pelvic and cranial anatomy to support the evolution of human-like pregnancy in the Pleistocene and open up possibilities for novel ways to explore the evolution of hominid gestation via dental variation.


Western Washington University


New Scientist


Collaborative paper published – Domesticated dogs in the Americas

After more than a year of international collaboration, our new paper on the Biological and cultural history of domesticated dogs in the Americas is now published. In it, we discuss the important of the Coast Salish dog (or wooly dog) for the PNW Indigenous textile industry. Huge thank you to all my coauthors, especially Drs. Segura and Sánchez-Villagra.

full paper available HERE

New course for Winter Quarter – Earliest Art and Culture

I am looking forward to teaching a new course next quarter, called Earliest Art and Culture (ANTH 490)! There are still spots available, so if you are looking for a 490 or WP3 course, please think about joining us. The description is posted below:

Earliest Art and Culture (ANTH 490 WP3) – 

What is art? What is culture? Are humans the only species that create art and culture? When did art and culture begin? And can we see the traces of these behaviors in the fossil record? These are just some of the questions we will explore in ANTH 490 Earliest Art and Culture. Topics of discussion include art in the fossil record, changes in technology during the Plio-Pleistocene, the evolutionary function of music, the interaction between culture and genetics, among others. Reading and discussion materials for the course will be based on literature assigned each week.

This course is a WP3 designed to offer students the opportunity to learn skills in scholarly writing. In this course, we will cover the basics of science writing, including searching for literature, learning about citations and references, summarizing academic papers, and writing an abstract. The course will culminate in a rough draft and final paper that is a literature review based on a topic of the student’s choice (related to the course materials).

Human EDJ study published in PNAS

Ancient human relationships revealed through teeth

October 5, 2020 – Bellingham, WA – Teeth can tell us a lot of things about our ancestors, and now, new work led by the Primate Evolution Lab at Western Washington University has shown that tooth shape can be used in place of DNA to investigate ancient population movement and genetic relationships in the past. The study, led by Dr. Tesla Monson of the Department of Anthropology at Western, compared DNA and tooth shape using micro-CT scanning technology to look underneath the hard enamel surface of teeth from 161 ancient humans living on every continent except Antarctica.

Micro-CT scanning is an advanced technique for looking at different layers of an object without any physical dissection. Using this method, scientists can take images of teeth and use technology to digitally segment each layer of the tissue until the layer they are interested in is visible. Dr. Monson and her colleagues at the University of Zurich used micro-CT scanning to investigate the enamel-dentine junction, an internal layer of teeth. “What’s really exciting about this work,” says Dr. Monson, “is that we have shown that you can use teeth to answer some of the same questions as DNA, which means that you don’t always have to rely on destructive DNA analyses to investigate human relationships in the past.” Many ancient human remains are extremely delicate and rare, and this study paves the way for investigators to avoid applying destructive processes whenever possible.

Teeth are extremely well preserved in the fossil and archaeological records and have a strong genetic signature, making them prime targets for investigating human origins. The enamel-dentine junction (EDJ) is the part of the tooth underneath the enamel surface – it is thus even more well-preserved, because it does not wear away over time through use, even with a very harsh diet. Hominid fossils, for example, often retain EDJ shape even when the enamel has been completely worn away. The goal of this study was to investigate whether EDJ shape reflects genetic relationships between individuals and can therefore be used in place of DNA. This study is the largest investigation of EDJ morphology to date.

Dr. Monson and colleagues compared the shape of the human EDJ with neutral genetic data, parts of the genome that are not under natural selection. “The correlation between neutral DNA and EDJ shape shows that individuals that are more closely related also have more similar tooth shape,” explains Dr. Monson, “so tooth shape can be used to reconstruct genetic relationships in the past. This means we can know more about how closely related fossil individuals were just by looking at their teeth. And we can track peoples’ historical migration around the globe from their tooth shape alone. This is just another example of how much teeth can tell us about human evolution.”

More about the study: The full study was published October 5, 2020 in Proceedings of the National Academy of Sciences and is titled, “Neutral evolution of human enamel-dentine junction morphology.” Contact the author to request a pdf copy of the research article. This study was funded by the Swiss National Science Foundation. For more information, contact tesla.monson@wwu.edu



New paper on hominid taxonomy

I am happy to announce that we have a new paper out investigating the validity of species vs. genus taxonomy in the hominid fossil record.

A genotype:phenotype approach to testing taxonomic hypotheses in hominids (Brasil et al. 2020)

We note that genus-level taxonomy is much more informative in the fossil record, particularly when using biologically-meaningful phenotypes. This work uses our previously described dental phenotypes (MMC and PMM; Hlusko et al. 2016) and was led by Dr. Marianne Brasil. This research continues to build on our findings that MMC and PMM are heritable, independent of body size and sex, and have strong phylogenetic signal in mammals (Hlusko et al. 2016, Monson et al. 2019, Zuercher et al. 2020). This is the second application of these dental phenotypes to the hominid fossil record, following previous work from my lab that used machine learning to assess dental evolution in the fossil record (Monson et al. 2018). Research on MMC and PMM is ongoing. But for now, enjoy this paper on the biological philosophy of taxonomy in the fossil record! 

New paper on bat dentition

I am proud to announce our new paper, out now in the Journal of Mammalian Evolution.
This builds from our work in primates (Hlusko et al. 2016) and boreoeutherian mammals (Monson et al. 2019).
This all woman author list was led by PhD student Maddie Zuercher. I trained Maddie to take dental measurements more than 4 years ago, when she was an undergraduate student at UC Berkeley. It’s so rewarding to see a mentoring relationship progress all the way through publication. So proud of her & the other former undergrad coauthors. Just remember undergrads: it’s never to early to get started in research!

New paper on forensic stature estimation

I am excited to share the results of an ongoing international research collaboration with scientists in Spain and Turkey. This work develops new regression equations for estimating stature from the tibia with important implications for forensics. Stay tuned for part 2 of the research, hopefully out sometime this summer! As always, please contact me if you would like a pdf copy of our paper.

Piecewise regression equations for estimating stature: an anthropometric study in Spanish females