People don't seem to realize that the reason many bones, paintings and the such are found in caves is simply because, well, they're caves. And therefore protected from the environment. If you die in a cave, and the structure of the cave is solid for hundreds of thousands of years, your bones and related human debris will make it.
Most people in the good old days we're talking about didn't live in caves, because you don't find 'em around every corner. But where they existed, they would of course move into this ready made shelter. Wouldn't you?
That's why caves are a good source record of human history.
What's interesting is that our ancestors would bother to go down into caves to do these paintings. They must've wanted them to last, and recognized what I just outlined.
Must be instinct.
From Cavers crawl their way into the depths of Southern Illinois
Standing in front of the entrance to Ava Cave, a cool breeze can be felt flowing from inside.
The entrance is small, and the only way to get inside the cave is to crawl on your hands and knees.
Outside it is a sweltering 90 degrees, but inside the cave it is a cool 58 degrees.
The first few feet of the 1.3-mile cave can only be tackled by crawling, but there is plenty of room. The really tight belly crawls will come later.
As the cavern opens up, there is more room to stand up for a little while, but up ahead lies a narrow passage and more crawling.
Shining a light on the cave walls reveals the traces of the people who have passed through in the past.
There are pieces of string scattered on the floor. The walls in some places look like a bathroom stall because people have spray painted obscenities in the cave.
In some places, care must taken not to get your hands cut on the broken shards of beer bottles left behind.