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By Diane Ainsworth, Public Affairs

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, ash and shell - that were left by native Californians 4,000 to 5,000 years ago. First excavated in 1902, the mounds have 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 bay shoreline.

"People were here from the start, and that's pretty significant," says Lightfoot. "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 year."

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. Anthropologists now know that the first native Californians lived on the Sonoma County coast (Duncan's Landing), in the Los Vaqueros area of Alameda County and at sites in Santa Clara County, about 10,000 years ago.

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," he 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 side-by-side 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 is also well known for his archaeological investigations of Russian sites in northern California.

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 1769-1775, they described very dense populations, with smoke rising from many villages around the Bay."

Clearly, bayshore people exploited a range of resources in prehistoric America. Closer examination of the mounds reveals that these indigenous peoples fed mostly on shellfish, including bay mussels, Pacific oysters and bent-nose clams, and hunted terrestrial mammals, such as elk, black-tailed deer and pronghorn. Wolf, fox, bear, skunk and raccoon also were part of their staple diet, Lightfoot says.

Masterful fishermen

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. Paddles, hooks, darts, spears, nets and clubs, all used to kill sea mammals, including otters, harbor seals, fur seals and sea lions, were recovered from the shell mounds.

Many anthropologists subscribe to the popular theory that California Indians "were not passive hunter-gatherers who simply collected the fruits of a 'wild' and 'pristine' land," Lightfoot says, "but were nurturing land managers who constructed a cultivated landscape through deliberate human intervention over many centuries."

They built and maintained habitats through techniques such as tillage, controlled burning, pruning, weeding and seeding the wildlands, he says.

Competing theory

A competing school of thought, first suggested by Nelson and other early archaeologists, suggests that prehistoric populations overexploited the shellfish beds in San Francisco Bay, forcing later generations to find alternative food sources. An abundance of mussel and oyster remains were found in the lower (earlier) levels of the shell mounds, Nelson reported in 1909. In addition, one mound at Ellis Landing was estimated to contain more than 17 million mollusk shells.

Later anthropologists argued that Nelson's theory didn't hold water, claiming instead that there was quite a bit of variation in estuarine habitats in San Francisco Bay 4,000 to 5,000 years ago. Most of it was brought on by the silting of the bay, rather than from changes in the Indians' dietary preferences.

Lightfoot believes there is truth in both of these scenarios: local people were managing their environment while, at the same time, exploiting and perhaps even overexploiting certain primary food sources. "The critical point is that prehistoric San Francisco was never a natural or pristine wilderness," he says. "Its ecology has been changing as long as people have lived here."

The challenge for future stewards of the environment, however, will be to find ways of safeguarding nature's ability to renew natural resources, despite the swiftness with which people today are altering the ecology.

The large size and number of shell mounds found in the Bay Area - this one is called the West Berkeley Mound - suggest a fairly large population of native Californians were living along the shore at least 5,000 years ago; early 20th century UC Berkeley archaeologists Nels Nelson and Max Uhle identified more than 425 ancient mounds. Photo courtesy of the Nels Nelson Archive, American Museum of Natural History.