Geoscience Reference
In-Depth Information
northward, through the Central Valley of California and into the wetland
environments of the San Francisco Bay region. h e oldest shell mound site
along the shores of San Francisco Bay—the West Berkeley shell mound—has
a basal age that dates to the mid-Holocene, or 5,200 years ago.
Along the Pacii c Northwest coast, the basal dates of a number of shell
mounds are mid-Holocene in age, suggesting that coastal populations
expanded there as well. Food resources expanded in that region, as they
did along the southerly California coast, when sea levels stabilized. h e
newly formed intertidal zone would have brought with it the expansion of
resources, such as shelli sh, which allowed human populations to grow and
construct the numerous shell mounds. Conditions also improved for salmon
migration, spawning, and development of juvenile salmon. Archaeologist
Knut Fladmark at Simon Fraser University proposed that an increase in the
abundance of sockeye and coho salmon, considered the single most impor-
tant Native American food resource in that region, led to an increase in
coastal settlements.
h e climatic backdrop of these changes based on evidence from the Pacii c
Basin suggests that the mid-Holocene was a period of increased La Niña
conditions, when the trade winds blew with more intensity. It is possible that
the La Niña conditions over the Pacii c were at least partly responsible for the
extended period of drought over the American Southwest.
Following the mid-Holocene drought, climate in the American West turned
cool and wet again during a period known as the Neoglacial. h e archaeo-
logical record contains evidence for increased human sedentism, cultural
complexity, and more advanced technology beginning about 4,900 years ago,
becoming even more widespread at er 3,800 years ago. As we will explore
further in the next chapter, the Neoglacial brought with it increased climatic
variability.
Search WWH ::




Custom Search