Last week, construction workers on San Francisco's new Transit Terminal unearthed a skeleton 60 feet underground. The life of the person whose bones they found reveals a lot about how rising water levels have changed life in the Bay Area over the past few thousand years.

The skeleton found last week hasn't been dated yet, but San Francisco blogger Burrito Justice points out that a skeleton found in a similar area, 15 feet lower, was dated at about 5,000 years old. Like the skeleton found last week, this earlier skeleton belonged to a Native American who lived in the San Francisco area when sea levels were very different from today.

Burrito Justice writes:

San Francisco Bay as we know it is relatively new — as the ice age ended, sea levels rose dramatically. 18,000 years ago, to get to the beach you would need to take the N-Judah past the Farallons, which were once hills by the sea. The Bay was a valley with a river running through it, and the Golden Gate was a waterfall . . . But as the waters rose the Farallons were cut off . . .

Around 10,000 years ago, the sea breeched the Golden Gate and continued to rise rapidly, filling the valley we now know as San Francisco Bay. There must have been settlements by the water — imagine each generation having to pull back, each high tide greater than the last.

San Francisco skeleton find sheds light on ancient Bay Area villages

Apparently the local Ohlone tribe told a story about how the port of San Francisco, currently facing the Bay, was long ago an oak grove. Could this piece of storytelling actually be an oral history of what it was like to live in the Bay Area when the region was a valley with a river running through it? Burrito Justice notes that geologist Brian Atwater wrote:

No known archeological site in central California appears much older than 5,000 years… One way to approach this problem is to assume that traces of the earliest central Californians have been covered by the rising sea. Given the rapidity of changes in sea levels and shorelines 5,000-10,000 years ago, sites of habitation located at that time along the shores of estuaries must now lie beneath mud and tidal water.

It's possible that the skeleton discovered last week is from one of these groups who lived in the San Francisco Bay during a time when there was no Bay at all. Sea level rises have transformed the human communities in this area for thousands of years. When rising waters force San Francisco to retreat inland over the next century, it will just be the latest phase of the Pacific Ocean burying evidence of human habitation.

Read more at Burrito Justice

Map of sea level rise by Lynn Ingram