Home https://server7.kproxy.com/servlet/redirect.srv/sruj/smyrwpoii/p2/ Science https://server7.kproxy.com/servlet/redirect.srv/sruj/smyrwpoii/p2/ Solving the mystery of a 13,000-year-old bone discovered on the California Channel Islands

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



Arctodus we reconstruction

Arctodus simus reconstruction compared to a human. Credit: Dantheman9758 / Wikimedia Commons CC BY-SA 3.0

The Channel Islands of California are known for their archaeological, biological, and paleontological significance and wealth, which includes some of the most important early human sites in North America. This significance only grows with new excavation, chemical and biomolecular techniques that expand our vision of this dynamic ecosystem and its enduring significance for both 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-haired bear, Arctodus simus, from the California Channel Islands. This fearsome animal ̵

1; weighs by some estimates 2,000 kg. – once roamed in different environments from Alaska to Mexico, but has never been found in such an isolated island context. While this is not the first strange mammal found on the California Channel Islands that was once home to a pygmy mammoth and a giant mouse, it is the first case of a potentially native megafaunal carnivore that would challenge earlier models of colonization and evolution. the biodiversity of the islands.

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

Short Faced Bear Toe Restored Daisy Cave

Two views of the short-term bear toe recovered Daisy Cave, San Miguel Island, California Channel Islands (University of Oregon # 514-6778). The excised bone indicates where the samples were taken for DNA, radiocarbon and protein analysis. Credit:
Excerpts from Figure 2 from: Mychajliw et al. 2020. Biogeographic problem solving reveals the late Pleistocene translocation of a short-haired bear to the California Channel Islands. Scientific reports, http://www.nature.com/articles/s41598-020-71572-z

“Found in a stratum dated to over 13,000 years ago, the bone posed a significant mystery,” said Jon Erlandson, a professor at the University of Oregon who has led research at Daisy Cave since the 1990s. Was it from a big grizzly or black bear? The sample rested safely in Erlandson’s laboratory for more than 20 years.

In 2016, the toe arrived at the Laboratories of Molecular Anthropology & Microbiome Research at the University of Oklahoma.

“From the moment I heard that this could be a unique specimen, I handled it with extra care. I remember having a hard time cutting out the bone piece; it was such a rigid, morphologically well-preserved specimen thanks to the cave environment. Fortunately, it is DNA was also well preserved, ”said Nihan Dagtas, who successfully extracted amplifiable DNA at the world-class cleanroom facility at LMAMR.

In parallel, the sample was analyzed for old bone proteins (collagen) at the University of Manchester in the UK and produced chemical fingerprints that best matched a reference to the spectacled bear from South America – the only living relative of the short face. . These two independent molecular analyzes combined with traditional morphological evidence for the shape and size of the toe confirmed its identity as unexpectedly belonging to a giant short-haired bear.

Torben Rick, who participated in the Daisy Cave excavations and is now at the Smithsonian’s National Museum of Natural History, was thrilled to use a number of new, minimally destructive technologies (aDNA, proteomics, etc.) to help solve the questions surrounding this mysterious bone. “When the results came back that this was a short-haired bear dated to about 17,000 years ago, we were all really fascinated by the implications for island biogeography and ecology,” Rick said.

Scientists were at first confused – what did a giant short-haired bear do so far away from its known territory on the California mainland? They developed a set of hypotheses to test whether it arrived on the island before or after death, and weighed the evidence.

If the bear died on the island, it could indicate that a native population of short-term bears swam to the islands and evolved for thousands of years along with the pygmy mammoths. Or did a single person swim to the island in search of a snack? The researchers suggest that a “pre mortem” arrival of the toe was unlikely, as it is the only specimen of the species ever found on the islands, and bears that die in caves are usually found intact.

The researchers then turned to a “post mortem” hypothesis: the toe was brought to the island by something or someone. “A human transport of the toe bone seems unlikely given its age and excellent conservation, but several animals – condors, eagles, gulls and others – are known to flush and transport bones and shells in coastal areas,” said Erlandson.

The research team suggests that the most likely mode of transport was wings. Chemical analyzes known as stable isotopes indicate that this bear opportunistically fed on the carcasses of marine mammals and perhaps put it at the right time and place for its own carcass to eventually be cleaned by a bird, such as a Californian condor or a bald eagle.

“We were able to integrate interdisciplinary toolkits, including morphology, ancient DNA, collagen fingerprint, radiocarbon dating, and stable isotopes, to develop a robust framework for hypothesis testing that allows us to explore the origins of this mysterious bone,” he said. Courtney Hofman, assistant professor of anthropology at the University of Oklahoma, co-director of LMAMR and senior author of the study.

Despite being once so widespread, there is considerable debate about the ecology and behavior of short-term bears, and available data are sparse. Previous studies that relied on tooth shape and cavities suggested that short-haired bears from Los Angeles’ famous La Brea Tar Pits ate large amounts of carbohydrates, while other studies using stable isotopes suggested that the species was dependent on animal protein in Alaska. and Canada. Surprisingly, this toe was the first sample to test dietary hypotheses in the same way in California.

“This little toe helped us lay the groundwork for tackling some big issues in paleontology,” notes Alexis Mychajliw, a postdoctoral research assistant at the University of Oklahoma, research assistant at La Brea Tar Pits and lead author of the study. “Southern California was filled with big carnivores 17,000 years ago, and it is possible that the opportunistic use of marine resources helped short-haired bears survive fierce competition. That is, until the climate changed and people arrived. ”

Reference: “Biogeographic Problem Solving Reveals Late Pleistocene Translocation of a Short-Haired Bear to California Channel Islands” September 16, 2020, Scientific reports.
https://www.nature.com/articles/s41598-020-71572-z




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