Our Next Program will be Sunday, March 26, 2023

It will be via Zoom  due to the uncertainty of Chicago area weather.

In April we will return to the Evanston Public Library for in-person meetings with the Zoom compliment.


"The 130 ka (MIS 6-5) Cerutti Mastodon Site:

History of Investigations, Results, Present Status of Research, and the Debate"

Dr. Tom Deméré

Curator of Paleontology and Director of PaleoServices

San Diego Natural History Museum, San Diego, CA


~~ 3:15 pm CST Zoom opens  ~~~ 3:30 pm CST Announcements and Program~~









Dr. Tom Deméré is Curator of Paleontology and Director of Paleo-Services at the museum. He received his B.S. in Geology from San Diego State University, his M.S. in Geological Sciences from the University of Southern California, and his Ph.D. in Evolutionary Biology from the University of California, Los Angeles. Tom has worked at the Museum since 1979, where he oversees paleontological research and collections activities, as well as the paleontological assessment and mitigation program. His research broadly involves documenting the Cenozoic biological and geological history of the southern California and Baja California region, with special focus on the evolutionary history and comparative anatomy of marine mammals and the regional Plio-Pleistocene record of marine and terrestrial biotas and paleoenvironments.


The talk will focus on the Cerutti Mastodon (CM) site, which yielded remains of a single American mastodon (Mammut americanum) associated with evidence indicating hominins used stone hammers and anvils to break limb bones and molars 130,700 ± 9,400 years ago. Taphonomic evidence for human agency will be presented, and includes bone impact features (cone flakes, bulbs of percussion, and an arcuate impact notch); stone impact and usewear features (negative flake scars, and angular fractures); bone, tusk, and stone distribution patterns (femoral shaft fragments clustered around a single large cobble, detached femoral heads positioned side-by-side, and a vertically oriented tusk); differential bone breakage (intact fragile ribs vs. fragmented limb bones); and bone, molar, and stone refits (80-cm displacement of pieces of a partial femoral diaphysis, 3-m displacement of pieces of a single molar, 3-m displacement of pieces of a single large cobble). Significantly, most CM bones and stones were enclosed within crusts of soil carbonate that establish a “chain of evidence” showing that breakage and positioning of objects at the site occurred many thousands of years ago before burial of the site. No knapped stones or cut-marked bones were recovered at the CM site, which is hypothesized to represent a bone-processing site occupied for a short period of time for a limited set of activities (expedient stone hammers and anvils used to break mastodon bones for marrow extraction and/or production of raw materials for bone tools). Reaction to the hypothesis for human agency also will be discussed, as well as the results of a follow-up study documenting the presence of bone residues on CM cobble hammerstones and anvils.


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