Are you familiar with the La Brea Tar Pits? Thirty thousand years ago this area was teeming with mammoths and sabertooths and other ice age creatures that would occasionally get stuck in the pits. Of course they’re not really filled with tar. It’s asphalt that bubbles up through shallow levels of the earth’s crust. Because they sank into the muck, the animals’ bones were well preserved, making La Brea one of the richest ice age fossil deposits in the world. Millions of bones have been found, and there are probably millions more to come.