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In the 1970s, student archaeologists excavated a shell midden on Santa Catalina Island in California. For decades, the bones and shells they discovered, which dated to more than a thousand years before European contact, were stored in paper bags at the Catalina Island Conservancy on the island. In 2018, Hugh Radde, a doctoral candidate in zooarchaeology at the University of California, Santa Barbara, began to look into those paper bags. His examination revealed that the Indigenous people living on the island sustainably harvested sea mammals from roughly 700 CE to 1450 CE.

“I don’t see any evidence of overexploitation in the way that suggests that Indigenous populations were mismanaging a resource,” says Radde, the author of a new study examining the strategies the Tongva used to hunt seals and sea lions.

Archaeologists have worked on Catalina Island for decades, so much so that some excavated remains still sit around in storage waiting to be analyzed.* “One of our mantras is there’s no need to put a shovel in the ground and start digging until we look at some of these older collections,” Radde says.

Focusing on the contents of the midden, Radde found that while nearly a third of the bones were from fish, including California sheephead, kelp bass, albacore, mackerel, rockfish, and moray eel, some 70 percent represented marine mammals—a much higher proportion than most Tongva middens dating to this period. The Tongva started living on Catalina Island at least 8,000 years ago, but they also lived on some of the other southern Channel Islands and parts of the mainland around Los Angeles.

In this midden, “the marine mammals were just blowing everything out of the water,” Radde says, adding that, by and large, these mammal remains were from California sea lions, though bones from sea otters, dolphins, and elephant seals turned up as well.

Further analysis showed that the remains were also almost entirely from subadults, with very few bones from sea lion pups or adults.

Previous research suggests that Indigenous people on some of the other Channel Islands had harvested sea lion pups, an approach that could have caused populations to decrease over the long-term. But by harvesting non-breeding subadults instead of pups, the Tongva would have had less of an impact on the sea lion population because one subadult provides as much meat as multiple pups.

It’s unclear how many marine mammals’ remains are in the midden since they are jumbled together, but it’s likely somewhere in the dozens rather than hundreds, Radde says—and this is spread over several centuries. Other middens discovered in the area so far don’t show nearly the same amount of pinniped remains.

Today, few marine mammals visit Catalina Island. But San Miguel Island, also in the Channel Islands, still has large California sea lion rookeries and haulouts. Some of the other Channel Islands host plenty of elephant seals.

The animal remains unearthed decades ago indicate that sea lions likely used Catalina Island as a haulout and possibly as a rookery at some point in the past, since subadults don’t usually travel too far from their place of birth.

Radde isn’t sure how the Tongva hunted the animals, but thinks they probably accessed them at haulouts using canoes known as ti’ats. Previous research shows ti’ats started to appear around the same time as the earliest dates of the shell midden. These boats, which were big enough to hold up to eight people, would have been about the right size for the Tongva to transport subadult sea lions. The carcasses of bigger sea lions would have been harder to move around.

“[Ti’ats] might have been what allowed them to get to farther places around the island or transport more meat back,” Radde says. “It’s a very nice piece of technology that increased transportation and access to the islands from the mainland.”

He speculates that the Tongva used these boats to get close to the haulout area, but probably didn’t hunt directly from the ti’ats as it would have been difficult to sneak up on sea lions from the water. “If you spook them, they will just bolt,” he says.

This discovery is “really important because we’re not managing our environment very well,” says Patricia Martz, president of the California Cultural Resources Preservation Alliance, an organization dedicated to protecting sites of cultural and historical importance in the state. “I think that in pre-[European] contact times, of course there were smaller populations, but they were doing a good job of managing the environment.”

“It is doubtful that the Indigenous peoples of California overexploited pinnipeds” such as seals and sea lions, she adds.

Martz, who has done research on sites on the Channel Islands and has found seal bones farther inland, says the study is well researched. She stresses that what took place on Catalina Island can’t be taken as a statement about all of coastal California, or even the Channel Islands as a whole. But it does provide a snapshot about how humans affected the ecology on Catalina Island in the past.