Complex sentence: A fossilised wasp nest overlaying cave paintings of a similar type has been tested as being 17,500 years old, making the rock art older and maybe dating to the last ice age, some twenty to twenty-five thousand years ago.
Split into simpler sentences: A fossilised wasp nest overlaying cave paintings of a similar type has been tested as being 17,500 years old. This means that the rock art is older than this and may date to the last ice age, some twenty to twenty-five thousand years ago.