The pits are one of the world’s best and most important sources of Ice Age fossils.
But for the animals, these tar pits meant death.
Animals mistaking it to be solid ground would wander in, become trapped, and eventually die.
Predators would enter to eat the trapped animals and also succumb to it.
As the bones of the dead animals sink into the asphalt, it soaks into them.
The lighter fractions of petroleum evaporate away leaving a more solid substance, which encases the bones.
The bones occasionally found in the tar were first thought to be those of unlucky cattle.
It was not until 1901 that the first scientific excavation of the pits were carried out.
The pits have, till now, yielded entire skeleton of large mammals such as mammoths and saber-tooth cats.
The oldest known material extracted from the La Brea seeps has been dated to 38,000 years old.
