Simple answer: we didn't.
What has been found in the La Brea Tar pits?
Over 1,000,000 bones have been excavated from the tar pits since 1901.
Researchers have found remains of saber-toothed cats, dire wolves, bison, American cave lions, mammoths, giant ground sloths, invertebrates, fish, reptiles, raccoons, rats, bats, shrews, rabbits, and squirrels.
Then my 4th grade teacher lied to us. And I’ve been there many times. Hmmm, same teacher also told me Pluto was a planet.
HA