Ancient humans might have weathered the ice age and mass extinction in San Diego

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The semi-arid climate was cooler, the now-dry landscape covered with expansive grasslands. Long before they were replaced with possums and rodents, this was the land of woolly mammoths and mastodons, whose main concerns probably would have been the five-foot-long dire wolves and saber-toothed cats trying to eat them.

This was the San Diego of 130,000 years ago, as it would have appeared to early humans who, according to controversial new research, may have lived there. Recently discovered stone tools and the broken bones of a mastodon these humans apparently attacked are evidence archaeologists may have gotten early human history completely wrong. Because up until now, researchers believed Homo sapiens or their predecessors were not in the Americas until about 20,000 years ago.

Around 135,000 years ago, sea levels were lower and what is now Siberia and Alaska were connected by a land bridge. That offered an easy route for bison and perhaps wooly mammoths to migrate from Asia to North America. Early humans easily could have followed, whether those “humans” were Homo sapiens, Homo erectus, Neanderthals, or little-understood Denisovans. But even if they were a different species, they were likely similar to modern humans, capable of verbal communication and with the knowledge of various survival skills.

Over many generations, they could have traveled from Alaska to southern California by continuing to follow migrating animals or by simply expanding down the coast. However they might have reached the area that would ultimately become San Diego, when they got there, they’d have joined ground sloths, giant armadillos, 12-foot-tall short-faced bears, lions, hyenas, cheetahs, giant beavers, moose, horses, and camels.

Judging from their ability to reach America and use stone tools, though, they clearly had some ideas about how to take care of themselves. They likely could use stones as anvils and hammers, and knew enough to extract marrow from animals they killed for nutrition. If they made it that far, they likely would have been able to make fire. They may even have been able to make boats and navigate over water.

Archaeologists excavate 130,000-year-old mastodon fossils in San Diego County.
Archaeologists excavate 130,000-year-old mastodon fossils in San Diego County.
Image: San Diego Natural History Museum

But in matter of fact, their traditions and lifestyle are a complete mystery. Twenty years ago, researchers began excavating a former construction site in San Diego County. Last month, they announced the discovery of mastodon bones that they’ve been able to date back to 130,000 years ago (give or take 10,000 years), which look like they were broken by humans, and rocks that look like human-made stone tools, but that can’t be dated. According to the experts who announced these findings, these are incredibly convincing signs that humans lived in San Diego some 130,000 years ago.

For some Native Americans, the findings confirm that scientists have been wrong about how long humans have been on the continent—even if the results don’t prove their particular cultural tradition.

“The Kumeyaay Nation has always believed through cultural stories that were passed down that the Kumeyaay Nation has been here a lot longer than scientists have wanted to substantiate,” says Cody Martinez, chairman of the nation’s Sycuan band. He said the discovery is “definitely adding a spotlight to what’s been the accepted, agreed-upon migration date.”

Others are more skeptical, if only because the next-oldest evidence of early humans in the region are the 13,000-year-old bones of a man on Santa Rosa Island, one of the Channel Islands about 25 miles off the coast of Santa Barbara. That significant gap in history has led the researchers to suggest the early humans in California 130,000 years ago may have died off in a failed colonization effort.

That idea, though, is purely speculative. These early humans would have enjoyed a Mediterranean-like climate, with evergreen shrubs and more than enough to eat. There would have been periods of more and less rain, and geological forces moving the coastline progressively westward. But otherwise, conditions should have been fairly stable, even as the world drifted into the Ice Age.

“It’s not like it iced over in California,” explains Daniel Fisher, a paleontologist at the University of Michigan. “On the coast it would have been a pretty benign place. There would still have been abundant marine resources. They could have moved inward from the coast and found herbivores to hunt and scavenge. They would have had to look out for the big carnivores but there’s always challenge in life.”

“If things ever got bad,” he adds, “they could have simply moved south.”

They wouldn’t have been able to return the way they came, but they probably wouldn’t have had any reason to. As generations passed, they probably didn’t even remember life across the Pacific, because cultural memories only go back so far.

Proving a continuous human presence in North America for 130,000 years, though, will require far more archaeological discoveries. Because even if these early humans timed their migration perfectly to avoid the Ice Age, which lasted from about 110,000 to 11,000 years ago, that alone wouldn’t have ensured their survival.

Tom Deméré, curator of paleontology at the San Diego Natural History Museum
Tom Deméré, curator of paleontology at the San Diego Natural History Museum, has been working on the mastodon site since it was first discovered more than two decades ago.
Image: Skype

“It’s harsh dispersing into a new world, or trying to colonize a new world. And we don’t know even know who these people were,” says Tom Deméré, curator of paleontology at the San Diego Natural History Museum.

These early humans could have suffered the same fate of the European who tried to colonize Jamestown in the 1600s, before succumbing to disease and starvation.

To survive, they would have needed to make it through the Late Pleistocene extinction event 10,000-20,000 years ago, when the continent lost three-quarters of its large mammals. If they managed to survive in California for more than 100,000 years only to die so recently, it would be a harsh lesson in just how deadly climate change can be. They would have died in a relatively modern North America, under conditions similar to those modern humans now face during the mass extinction currently underway.

In any case, Deméré says, researchers need to continue searching for more sites from the same period. As convincing as the recently discovered mastodon site may be, acknowledging the discovery means accepting a complete paradigm shift in the history of human migration.

“I was always puzzled why there weren’t records of humans here earlier than 15,000, 20,000 years ago,” Deméré says. “I think that our site adds a new chapter, if it becomes more widely accepted, a new chapter in our understanding of colonization attempts.”