Fifteen thousand years ago, the Bay Area didn't have a bay — but it did have plenty of mammoths, saber-toothed tigers and other megafauna.
During the last ice age, what we now know as the San Francisco Bay was a wide, grassy valley teeming with life.
The lush valley was home to everything from giant 2,000-pound ground sloths to short-faced bears, which sound cute but were much bigger than present-day grizzly bears and could run 40 miles an hour to chase down their prey.
One of the most exciting paleontological finds — which included bones from three mammoths and one giant bison — happened 40 years ago at a construction site on the corner of Columbus and Pacific streets in San Francisco.
Amazingly, scientists were given exactly two hours to study the site and remove the bones before they were shooed away.
Mustn't slow progress, after all.
So next time you gaze out over the bay, picture herds of mammoths and giant bison grazing in a wide, grassy valley, bisected by a mighty river as it flows toward an ancient ocean some 30 miles west of the Golden Gate.
But remember to keep your eyes peeled for a hungry short-faced bear.