At the very end of Snowpiercer, right after the girl with the child gets out of the crashed train, they see a white polar bear. What did that signify?
Director Bong Joon-ho talked with Vulture about this very subject a few weeks back. His take? That the ending is optimistic
They have no memory of what it's like to be on the Earth. For them to procreate, it's going to take a little time. So, for me, it's a very hopeful ending ... But those two kids will spread the human race ... I don't really feel everyone must die. I hope there were other survivors who lived through the avalanche, I just didn't have the means to shoot that ... You realize later on that the kids are the ones keeping this engine going, and this machinery intact. The engine is itself is on its way to extinction along with cigarettes, and other goods. Extinction is a repeated word throughout the film. But outside the train, life is actually returning. It's nature that's eternal, and not the train or the engine, as you see with the polar bear at the end.