These caves in China were perfect homes for early humans. They were in use around 300,000 years ago, and at five thousand feet above sea level, they were safe from rising tides.
At this height, there wouldn't have been any animals, and yet they're full of animal bones including rhinos. The bones have indentations on them from stone tools, so they must have been hunted by our ancestors - but how and why were they brought up to such a height?