Short answers, pulled from the story.
The Australia continent is also called Sahul, Meganesia, Australinea, and Australia-New Guinea, each name proposed to distinguish it from the country of Australia. The name Sahul derives from the Sahul Shelf, a part of the continental shelf. Meganesia, meaning great island or great island-group, was proposed in 1984 and is widely used by biologists; Australinea was coined by biologist Richard Dawkins in 2004.
The Australia continent includes mainland Australia, Tasmania, the island of New Guinea (comprising Papua New Guinea and Western New Guinea), the Aru Islands, the Ashmore and Cartier Islands, and most of the Coral Sea Islands. The continental shelf underlies all these landmasses, and during the Last Glacial Maximum around 18,000 BC they were connected by dry land.
The Australia continent has a total land area of 8.56 million square kilometres, making it the smallest of the seven traditional continents. It is also the lowest, flattest, and second-driest continent on Earth after Antarctica. Because it sits in the middle of its tectonic plate rather than near a boundary, it is the only continent with no active volcanic regions.
Indigenous Australians arrived on the continent at least 50,000 years ago, based on archaeological evidence, with more recent research suggesting possibly 65,000 years ago. The earliest known human remains from the continent were found at Lake Mungo, a dry lake in southwestern New South Wales. Papuan habitation in New Guinea is estimated to have begun between 42,000 and 48,000 years ago.
Australia has high endemism because of long geographic isolation, tectonic stability, and an unusual pattern of climate change. About 83% of its mammals, 89% of its reptiles, and 93% of its amphibians are endemic. The continent's northward drift during a period of global cooling kept temperatures relatively stable, allowing species to evolve in isolation for roughly 40 million years.
Papua New Guinea has over 820 indigenous languages, representing 12% of the world's total, making it the country with more languages than any other on Earth. Most of these languages have fewer than 1,000 speakers. The country's extraordinary cultural and linguistic diversity stems from the long isolation of the more than 7,000 distinct cultural groups spread across its mountainous terrain.