Geoscience Reference
In-Depth Information
Despite this enormous loss, however, the achievements of Nelson and his
successors have helped us piece together a more complete picture of human
life during the Holocene, including the Neoglacial. As the droughts of the
mid-Holocene gave way to the wetter Neoglacial, the pace of mound-building
increased, as shown by radiocarbon dating of successive shell and soil layers of
the West Berkeley shell mound. h e so-called “Middle Period,” from about
4,000 to 1,450 years ago, was thought to have been a “golden age” of shell
mound activity, with the number of mounds around the Bay Area reaching
a peak in terms of population numbers and year-round occupation.
If we visualize San Francisco Bay during that time, the curious mounds
scattered around its margins were oblong—up to 500 feet long and 30 feet
high—and would have been dominant features of the shoreline. We might see
smoke curling up from village i res as the people rested from their foraging and
prepared their meals. h ey had for many centuries made the marshes their home
for part of each year at er sea levels had stabilized 6,000 years ago, allowing the
expansion of mudl ats and tidal marshes. h ese, and the rocky intertidal zone
and associated ecosystems, supported an abundance of coastal resources. h e
people caught i sh and harvested mussels, clams, and oysters from the shores of
the bay. h ey used rushes that grew close to the channels and in the fresher parts
of the marsh for building their homes and making baskets to carry implements
and food. h eir drinking water was obtained from local creeks that drained the
nearby hills, and they foraged riparian forests surrounding the creeks for berries,
roots, and herbs. h ey hunted deer, rabbits, birds, and other game animals.
h ere were challenges to permanent habitation, however. h e Neoglacial
period was marked by more frequent rains and increased river l ows that
raised the shoreline, and storms threatened coastal settlements that were
unprepared for them. h e shell mound villages represented a creative
response to this challenge: residents began “piling up” rather than “carving
out” a living. As kitchen waste from each household, including the remains of
cooking i res, was collected and deposited outside the simple huts, it became
part of a continually rising ground surface. h e ground and the mounds rose
steadily, fast enough for the villages to keep up with the rising tides that each
year reached a little higher onto the marsh. h e recycling habit of the mound
builders was not just good housekeeping but also an essential community
service and survival tool. h ese mounds therefore contain a stratii ed archive
of the lifeways, environments, and climates of the region over the past several
thousand years, and they suggest that the climate was indeed wetter, with
higher rates of river inl ow, during the Neoglacial.
