More on Mollusks: Trans-Holocene Shellfish Exploitation on the California Coast

Comparing allometrically estimated biomass of shellfish versus vertebrates exploited throughout the Holocene reveals that many coastal Californians relied heavily on readily accessible invertebrates for dietary protein. During the Paleocoastal occupation of the coast, shellfish represented as much as 92% of consumed dietary flesh. Data show that this dependence lessened over time, coinciding with an overall reduction in total quantity of consumed animal flesh. The causes of this change are unclear, but it appears to have begun after 9000 BP and involved a gradual increase in the use of vertebrates for the remainder of the Holocene. Considering the preponderance of shellfish in the diet, the increased use of vertebrates would have done little to compensate for the decline in shellfish biomass, especially considering the growth of coastal populations. To sustain themselves, coastal Californians appear to have increased intake of plant resources.