PCAS General Meetings

Monthly lecture meetings feature noted archaeologists and anthropologists who provide insight into a variety of topics. Lecture meetings are held at the Irvine Ranch Water District Community Room, 15500 Sand Canyon Avenue (between the I-5 and I-405) in Irvine, on the second Thursday of each month, at 7:30 pm. Meetings are free and open to the public. See vicinity and detail maps of PCAS meeting location.

The Irvine Ranch Water District neither supports nor endorses the causes or activities of organizations

that use the District’s meeting rooms which are made available for public use.

Many past PCAS lectures are available on the PCAS YouTube channel.

PCAS Zoom Meetings  


May 11, 2023

In-Person and Zoom Meeting (Speakers will be present at the in-person meeting.)

Lauren Biltonen, Aimee Montenegro, and Paul Langenwalter

Archaeological Investigations at CA-ORA-423, a Multicomponent Site in the Lower Aliso Creek Drainage, Orange County, California

CA-ORA-423 is a multi-component occupation site located in the Aliso Creek drainage of southern Orange County, California. The site contains a modest material culture associated with a number of occupations spanning a period in excess of 4,000 years. The site is average in size for the lower part of the Aliso Creek drainage, straddling perhaps half of the modern flood plain to a depth exceeding four meters. It consists of a stratigraphically complex midden composed of fluviatile sediments with varying concentrations of artifacts and ecofacts situated on a basal paleosol and capped veneer of top soil. The initial occupation appears to be situated on a basal paleosol developed from a marsh.

During the 1992–1993 rainy season, erosion exposed three human burials in the lowermost occupational stratum. These burials were recovered, documented, and repatriated the following spring. The 1993 and later excavations at ORA-423 recovered chipped stone, groundstone, hearths, fire-affected rock scatters, and a dog burial, as well as two additional human burials. Chipped stone artifacts in the assemblage include projectile points, scrapers, and utilized flakes. The projectile points are of types associated with the use of atlatl and dart in the earlier strata, and bow and arrow in the upper-most stratum. Debitage was present in small amounts. Groundstone artifacts include pestles, manos, and a metate. Bone and shell artifacts include awls, fishing equipment, and items of adornment.

Bone and shell ecofacts were recovered throughout the midden. The marine invertebrates are dominated by mussels and associated species typically utilized along the Orange County coast during the Milling Stone, Intermediate, and Late Periods. All were procured from nearshore and tidal zone habitats. The vertebrate assemblage includes evidence of fishing along with mixed small to large game procurement. The fishes are nearshore open water and kelp associated species. The terrestrial mammals used for food include rabbits and deer. The dog was a large or common Indian dog rather than the smaller Techichi. Its burial indicates more complex human-animal activity at the site. It was intentionally buried in a curled position with its forepaws and hind paws immediately adjacent to one another. Whether the burial was that of a pet which died or sacrificed during property destruction at the time of its owner’s death is not known.

Lauren Biltonen is cross-trained in archaeological and paleontological fieldwork, with experience in survey, excavation, monitoring, curation, and reporting. She has participated in field studies in central California, documenting, and excavating multiple sites with features ranging from pictographs to monuments, and a cave site. Her undergraduate fieldwork was at the Hope Hall Mammoth Site working on the excavation, curation, and reporting of a Columbian mammoth from the Rancholabrean. As a Research and Teaching Assistant, Lauren has worked as an Archaeological Crew Chief with Heritage Resource Consultants on bioarchaeological projects in Los Angeles and Orange Counties. Presently, Lauren works as an Archaeologist for Duke Cultural Resources Management participating in archaeological and paleontological surveys and construction monitoring projects in southern and eastern California.

Aimee Montenegro is a cross-trained archaeologist/paleontologist with experience in survey, excavation, monitoring, curation, and reporting. During her tenure as an undergraduate, she participated in several field investigations to collect data from California’s Central Valley, recording multiple sites with archaeological features, including pictographs, bedrock mortars, and milling slicks. She also participated in the on-campus excavation, curation, and reporting of a Columbian mammoth from the Rancholabrean North American Land Mammal Age (NAMA). As a Collections Intern at the Natural History Museum of Los Angeles, she participated in the conservation and curation of vertebrate fossils, as well as the mapping of associated paleontological localities. As an Archaeological Crew Chief with Heritage Resource Consultants, Aimee participated in archaeological excavations in Los Angeles and Orange Counties. Currently, works as a Cross-Trained Field/Lab Technician with Applied Earthworks and has served as a lead field technician on a number of surveys and construction monitoring projects for archaeological and paleontological resources during land development in Los Angeles, Orange, and Riverside Counties.

Paul Langenwalter is past-Chair of Anthropology at Biola University where he taught archaeology and biological anthropology. His research focuses on the human-animal interaction sphere (economic use of animals, prehistoric dogs, and animal ceremonialism), bioarchaeology, and religious ritual among the peoples of California and Oceania. Currently his work is centered in central and southern California, with projects addressing the archaeology and history of the Fresno River area involving rock art, reservation period conflict, ethnicity, and subsistence. Other projects involve ancient DNA and gene flow in southern California, the Pleistocene paleontology of the eastern Los Angeles Basin, and the renovation of orphaned collections.


June 8, 2023

In-Person and Zoom Meeting (Speaker will not be present at the in-person meeting.)

Dr. Nathan Nakatsuka

Genetic Evidence for Ancient Population Shifts and Migrations in Central and Southern California

California, prior to European contact, harbored more linguistic diversity than all Europe, and studies of language relationships, archaeological evidence, and traditional oral histories have led to many hypotheses about movements of people over the minimum of 13,000 years this region has been occupied. In the absence of ancient DNA, it has not been possible to test directly alternative hypotheses about the spread of groups with distinct biological ancestry. Working collaboratively with local Indigenous groups in California and Mexico, we report genome-wide data from 87 ancient Californian individuals and 40 ancient Mexican individuals ranging from 7,600 to 200 years old (BP), which we co-analyze with previously reported data. We find evidence for movement of ancestry related to ancient and present-day individuals from northwest Mexico, who would have likely spoken Uto-Aztecan languages, arriving in southern and central California from at least 5,300 BP that ultimately reached its highest level in regions where Uto-Aztecan speakers currently reside. Ancient individuals from Baja California share more alleles with the earliest (5,200 BP) central California individual than with later Indigenous Californians, potentially reflecting the first “Hokan” language associated populations in central California having a high degree of relatedness with groups like those in Baja, and subsequent mixture transforming much of their ancestry. We find that ancient California individuals harbor increased affinity to the ~12,800 year old Anzick-1 individual associated with the Clovis culture compared to ancient northwest Mexico groups, which are on a different ancient lineage. Lastly, we find that some of the ancient groups from California and northwest Mexico had very small population sizes, similar to that of ancient Patagonian groups and significantly lower than ancient groups from the Andes and the Caribbean Ceramic period.

Nathan Nakatsuka was born and raised in Honolulu, Hawaiʻi. He graduated from Kamehameha Schools Kapālama High School then attended Harvard College, earning an AB in Chemical and Physical Biology. He then attained an MPhil in Genetics from University of Cambridge on a Gates Cambridge scholarship, working at the Wellcome Trust Sanger Institute with Inês Barroso. Nathan received his MD at Harvard Medical School in the Harvard-MIT Health, Sciences, and Technology MD track and his PhD from the Systems, Synthetic, and Quantitative Biology PhD program working in the laboratory of David Reich on population genetics of South Asia and the Americas. During his PhD the majority of his work focused on studying ancient DNA to uncover the ancient history of North, Central, and South America. He currently is a postdoctoral fellow at New York Genome Center in the laboratory of Rahul Satija working on single cell analyses of neuropsychiatric traits.

No meetings in July and August


September 14, 2023

Dr. Philip de Barros

Exciting Pottery Discoveries in the Coachella Valley: 14th Century Ceramic Firing Pits in the City of Coachella?


October 12, 2023

Dr. Ian Straughn

Archaeology in Interim Spaces: Excavation and Pedagogy at the Historic Bonita Camp Site on the UCI Campus


November 9, 2023

Dr. James Kennett

Massive Effects and Consequences of the Younger Dryas Cometary Impact with Earth 12,800 Years Ago


December 14, 2023

Dr. Scott Sunell