The Transbay Transit Center will be an epicenter for the future of regional transit, but this week workers found something from the site's past - 11,000 years ago to be more specific. A woolly mammoth tooth and part of a jaw were found 110 feet below the surface by a crane operator at the east end of the Transbay Transit Center jobsite. Though construction sites will often find artifacts from the past few hundred years of human settlement, this find from the Pleistocene Period is definitely rare (though artifacts of the same age were found in downtown Los Angeles). According to a press release from the Transbay Joint Powers Authority, the tooth (which is about a foot in length and 8 inches tall) and jaw date back to when the Bay Area was a grassy valley much like the Serengeti of East Africa and home to saber tooth cats, giant ground sloths, mastodons, elk, tapirs, short-faced bear, and bison. The TJPA intends to donate the artifacts to the California Academy of Sciences.