San Francisco Bay’s 5,000-year history of human transformation
Shell mounds along the shoreline reveal a bay that has never been uninhabited, anthropologist says

By Diane Ainsworth, Public Affairs

10 July 2002 | Human habitation of the San Francisco Bay is as old as the bay itself – even older. However, says anthropologist Kent Lightfoot, people today are altering the bay’s ecology more rapidly than did the native Americans of millennia past.

Lightfoot knows because he has logged a fair amount of time sifting through shell mounds along the bay. They contain prehistoric artifacts — built up from tons of rock, soil, shell — that were left by native Californians 4,000 to 5,000 years ago. First excavated in 1902, the mounds preserved human remains, graves, house floors, hearths, roasting pits and other domestic features, and a diverse range of animal and plant remains, left by local hunter-gatherers who thrived along the shoreline.

“People were here from the start, and that’s pretty significant,” he says. “They witnessed the creation and expansion of the San Francisco Bay system. They were here when sea levels were much higher and the Golden Gate was under water, about 10,000 or 11,000 years ago. They’ve been here ever since.”

A 5,000-year perspective
Lightfoot — who presented “A 5,000-Year Perspective of the Human Transformation of the Bay” recently, on behalf of the Berkeley Natural History Museums — believes that San Francisco Bay is “an excellent setting in which to view the symbiotic relationship of humans and the environment over the last 11,000 years.”

Early survey work by two Berkeley archaeologists, Max Uhle and Nels Nelson, laid the groundwork. Just after the turn of the century, they identified and recorded some 425 prehistoric shell mounds. From that survey, later researchers were able to show that the first native Californians lived about 10,000 years ago, along the Sonoma County coast (Duncan’s Landing), in the Los Vaqueros area of Alameda County and at sites in Santa Clara County.

As sea levels began to decline 4,000 years later and more shoreline appeared, human settlements began to dot the landscape, Lightfoot says. The San Francisco, San Pablo and Suisun bays all started to emerge.

“Thousands of acres of intertidal mud flats, and salt and brackish tidal marshes, were beginning to take root and thrive during the period of 6,000 to 2,000 years before present,” Lightfoot says. “The chronology of archaeological sites follows the establishment of tidal wetlands around the bay. The earliest bayshore sites date to about 5,000 to 4,000 years ago.”

Pre-colonial inhabitants
The large number and size of the shell mounds — some covering the length of two football fields and rising 30 feet in the air — suggest that a fairly large population of native Californians lived in the region long before Spanish, Mexican and Russian peoples began to colonize the area, says Lightfoot, who conducts archaeological investigations of Russian sites in Northern California as well.

Nelson, in fact, was not able to find all of the mounds before they were destroyed by urbanization. Early population density has been difficult to estimate because of that, Lightfoot says.

“On the one hand, not all of these mounds were probably occupied at the same time,” he says. “Many appear to have been used over multiple centuries, so we had overlapping occupation spans. Certainly when early Spanish explorers entered the Bay Area between 1769 and 1775, they described very dense populations, with smoke rising from many villages around the bay.”

They were masterful fishermen and traveled short distances in tule balsas, small boats constructed from tule reeds that could hold up to three people at a time. Lightfoot has found paddles, hooks, darts, spears, nets and clubs, all used to kill sea mammals, including otters, harbor seals, fur seals and sea lions, in some of his prized shell mounds.

Lightfoot thinks the early inhabitants exploited a range of resources; shellfish, including bay mussels, Pacific oysters and bent-nose clams, comprised most of their diet; elk, black-tailed deer, pronghorn and an occasional fox, wolf or raccoon supplemented it.

But he maintains that the indigenous peoples of the bay were passive, not aggressive, hunter-gatherers, that they were “nurturing land managers who constructed a cultivated landscape through deliberate human intervention over many centuries.” They cared for the shoreline through tillage, controlled burning, pruning, weeding and seeding. To look back 5,000 years, he says, is to see an ecology that has never been truly untouched by human hands.