Solve the mystery of a 13,000 year old bone discovered on the California Channel Islands

Arctodus simus reconstruction compared to humans. Credit: Danthmann 9758 / Wikimedia Commons CC BY-SA 3.0

The California Channel Islands are noted for their archaeological, biological, and paleontological significance and richness, including some of North America’s most important early human sites. This importance is only increasing with new excavation, chemical and biomolecular techniques, expanding our vision of this dynamic ecosystem and having equal importance for humans and wildlife.

Today, a team of researchers from the University of Oklahoma, the Smithsonian National Museum of Natural History, the University of Oregon and others report the first occurrence of the extinct giant short-faced bear, Arctodus simus, from the California Channel Islands. This sinister animal – by some estimates weighs 2,000 pounds. – Once roamed in diverse environments from Alaska to Mexico, but never found in such an isolated island context. While it is not the first strange mammal found on the California Channel Islands, which was once home to a piggy giant and giant rat, it is the first case of a possible native megafannel carnivore, which would challenge previous models of colonization and Development of biodiversity of islands.

This small bone, excavated in 1996, was long believed to be from a seal, but experts suggested it was from a bear – the first and only bear ever recorded for California’s Channel Islands.

Small faced bear toe daisy cave recovered

Two scenes of small-faced toe recovered at Daisy Cave, San Miguel Island, California Channel Islands (University of Oregon # 514-6778). The cut bone indicates where the samples were taken for DNA, radiocarbon and protein analysis. Credit:
Excerpt from Figure 2: Mychajliw et al. 2020. Lyle Pleistocene’s translation of a small-faced bear in the California Channel Islands to address a biographic problem. Scientific Report,

“Found in a letter dated 13,000 years ago, Bone uncovers an important secret,” said John Erlandson, an Oregon professor who has directed an investigation into Daisy Cave since the 1990s. Was it from a big brown or black bear? This specimen safely rested in Erlandson’s laboratory for over 20 years.

In 2016, the leg bone reached the laboratories of molecular anthropology and microbiome research at the University of Oklahoma.

“From the moment I heard that it could be a unique spec, I handled it with extra care. I remember having a hard time cutting and removing a piece of bone; It was such a rigorous, morphologically well-preserved specimen, thanks to the cave’s atmosphere. Fortunately, its DNA It was also well preserved, ”said Nihan Dagtas, who has successfully extracted amplified DNA in LMAMR’s world-class clean room facility.

In parallel, the sample was analyzed for ancient bone protein (collagen) at the University of Manchester in the UK, producing chemical fingerprints that most closely matched the reference to spectacled bears from South America – The only surviving relative of the short-faced bear. These two independent molecular analyzes, combined with traditional morphological evidence of toe size and shape, confirm its identity, unexpectedly, for a giant short-faced bear.

Toben Rick, who participated in the excavation of Daisy Cave and is now in the Smithsonian National Museum of Natural History, excited to put a suite of new, minimally destructive technologies (aDNA, proteomics, etc.) to help solve this mysterious question. Were. Bone. “When the results came back that it was a small-faced bear dating back to 17,000 years ago, we were all really concerned about the island’s biography and implications for ecology,” Rick said.

Researchers were previously surprised – what was a giant short-faced bear doing away from its known range on the California mainland? He developed a set of hypotheses to test whether it came to the island before or after death, and weighed the evidence.

If the bear dies on the island, it could mean that a native population of short-faced bears swam across the islands and evolved with the pygmy mammoth for thousands of years. Or a single person swimming on the island in search of breakfast? Researchers suggest that the arrival of the “former mortem” in the toe was not possible, as it is the only specimen of the species found on the islands, and bears dying in caves are usually found intact.

Then, the researchers turned to a “postmortem” hypothesis: the toe was brought to the island by someone or something. Erlands said, “A human transport of the foot bone is unlikely given its age and excellent preservation, but many animals – conductors, eagles, seagulls, and others – are known to scrape bones and shells in coastal areas.” ”

The research team suggests that the most likely mode of transport was the wing. Chemical analysis known as stable isotopes suggests that this bear was opportunistically feeding on marine mammal carcasses, perhaps putting it at the right time and right place for its own carcass, such as California’s Condor Or by a bird like bald eagle.

“We were able to integrate interdisciplinary toolkits including mystical science, ancient DNA, collagen fingerprinting, radiocarbon dating and stable isotopes to develop a robust hypothesis testing framework that allows us to trace the origin of this mysterious bone, “Said Courtney Hoffman, assistant professor. Co-director of anthropology, LMAMR at the University of Oklahoma, and senior author of the study.

Despite being so widespread once, there is significant debate over the ecology and behavior of short-faced bears, and the available data are sparse. Previous studies that relied on tooth size and cavities suggested that short-lived bears from Los Angeles’ famed La Brea tar pits ate large amounts of carbohydrates, while other studies using stable isotopes showed animal proteins in Alaska and Canada Suggested species dependent on. Surprisingly, this toe was the first specimen in California to test the diet hypothesis in the same way.

“This little leg helped us form the basis for addressing some of the big questions in paleontology,” said note Alexis Machajliv, a postdoctoral research associate at the University of Oklahoma, La Brea Tar Pits, research associate and lead author of the study. “Southern California was packed with large carnivores 17,000 years ago, and it’s possible that opportunistic use of marine resources helped short-faced bears avoid some tough competition. That’s why until the weather changes Haven’t arrived, humans still. ”

References: “Lele Pleistocene Reveals a Little-Faced Bear in the California Channel Islands to Solve a Biographic Problem” September 16, 2020, Scientific report.