Antarctic prehistory introduction
Life has been on earth for about 3.5 billion years. Until about 575 million years ago, all was microscopic plant life.
Before that time life in the Antarctic was very different from the way it is now. Antarctica was part of Gondwana and was fully vegetated with all the animal and plant life that existed elsewhere on the supercontinent. Of course, there were regional differences, just as there are differences between the animals and vegetation in parts of Australia.
When animal life burst forth on earth, initially all in the marine environment, Antarctica lay along what is now Australia's southern margin but the pair was rotated anticlockwise about 90° and the equator ran though both continents. At about 400 million years, Gondwana moved dramatically and Antarctica took up its place over the South Pole, but moving a little from time to time. Thus the South Pole has not always been within Antarctica but always very close to it.
When animal life evolved, carbon dioxide content of the atmosphere was much higher than at present and some estimates put it at 15–20 times as high. As oxygen content grew, the time came when some oxygen could reach the stratosphere, be converted to ozone and give protection from ultraviolet rays. When this happened, plant life moved from the oceans to the land and then land animals evolved to feed on the plant life.
At about 130 million years, Gondwana really began to disintegrate, with India and South America-Africa departing. At about 90 million years, Australia began to move very slowly, and the links between Australia and Antarctica remained very strong until about 55 million years when Australia began moving north quickly, allowing Antarctica to become isolated for the first time since animals evolved. At about 30 million years, Antarctic Circumpolar circulation evolved, the Southern Ocean began to circulate around the southern world and the modern Antarctic environment evolved.