Complex sentence: Gibraltar's Neanderthals may have been the last members of their species; they are thought to have died out around 24,000 years ago, at least 2,000 years after the disappearance of the last Neanderthal populations elsewhere in Europe.
Split into simpler sentences: Gibraltar's Neanderthals may have been the last members of their species. They are thought to have died out around 24,000 years ago, at least 2,000 years after the extinction of the last Neanderthal populations elsewhere in Europe.