It is home to many creatures that have been evolving apart from the rest of the world for millions of years.
When the supercontinent Pannotia broke up in the Precambrian, it split into five parts. Four of these parts would continue smashing together and splitting up, eventually becoming the modern continents. But the fifth fragment, only about the size of New Zealand, dodged the geological piefight altogether by riding along the Pacific Rim. All that is left of that fifth Pannotian fragment today is Henders Island.