coles' excavation of the largest shellmound (d. 2015) during the 1960s, which produced carbon-14 dates of 1,700–2,000 years before present for the oldest materials in the mound. coles estimated that the ohlone occupation of the site may date back more than 3,000 years. his study found bones from cormorants, ducks and other waterbirds (but no pelicans). marine mammal bones included harbor seals, sea lions, porpoises and whales. these early residents used atlatls and harpoons with bone points. even though the mound showed evidence of large catches of fish, especially herring, there were no fishhooks found, indicating that perhaps nets were used. mollusks such as mussels, oysters, and clams were a large portion of the diet.