Humans

So, who makes it to this Green Antarctica, and do they stay?

The initial waves of human expansion reached into Southeast Asia approximately 60,000 years ago. Australia was colonized 40,000 years ago. The Americas no longer than perhaps 30,000 years ago, or more likely, as recently as 12,000 years ago

On the other hand, Humans did not make it to Iceland, Madagascar or New Zealand until about 1000 years ago, more or less. The big Island groups of the Pacific, and the large islands of the Atlantic - the Azores and Canaries are all within the last two thousand years. All of it was seafaring cultures.

So, what are the prospects for non-European colonization of Antarctica? Here's my guesses:

#1 The Austro-Asian Invasion - Roughly 60,000 years ago to 30,000 years ago (probably in the later phases). Apparently hunter gatherer cultures, diminutive people with at least some capacity for short range boat travel, and a relatively decent neolithic tool kit. The most likely route would be an boat from the Tasmanian population blown off by a Hurricane getting caught up in the circumpolars, and managing to survive the journey. Given that Australia would have to be colonized first, this might but our colonization event post-Australia's - so let's say between 30,000 years ago and 10,000 years ago.

What are the chances? Well, over a twenty thousand year span, not too bad. But the odds are long that a boat blown off course would have enough breeding age females to start a population. Also, Antarctica can be a pretty tough place, particularly the winters. The most likely events are the occasional boatload of starving, malnourished warriors who show up thrive or eke out a living for a while, and then die off in the winter. Even with women, the usual outcome would be die in the winter.

But with incredible amounts of luck, you might get some people making it through the winter, and a viable colony starting up. But given the rigors, it's going to expand very slowly and be touch and go for a long time. This may give Antarctic flora and fauna an opportunity to cope with the human presence and avoid extinction.

Also, the privations and extreme seasonality, the likely patterns of animals and vegetation may allow for the emergence of agriculture and civilisation. If anyone wants to go there, enjoy.

Most likely outcome though, is that the Austro-Asian invasion never happens, or fails.

#2 Austronesians - The Austronesians emerged, apparently out of Formosa, some 3000 to 5000 years ago, and gave rise to a number of seafaring peoples, including the Indonesians, Malay, Lapita and Polynesians. These cultures, equipped with fairly sophisticated boats and navigation achieved some of the most astounding seafaring feats of the ancient world.

In particular, the Malay managed to cross from the Indonesian archipelago, through the Indian Ocean to settle Madagascar, an astonishing sea voyage. The Polynesians crossed the Pacific, settling places as remote as New Zealand, Hawaii, Rapa Nui, and apparently reaching South America.

Antarctica would be at the extreme limits of voyaging capacity. So its likely that discovery and colonization would have been in the last thousand years.

But there's a problem. Even assuming that mighty seafarers like the Polynesians or the Malay get there, and get there in sufficient numbers to try and colonize, their culture and technology, and in particular, their agricultural package is tropical. The climate, seasonality and extreme winter/nights of Antarctica are going to be tough to cope with.

So the likely outcome is shoreline hugging fisherman/hunter/gatherer cultures, perhaps something like a version of the inuit.

Khoi- Nah - The Khoi-San peoples of Southern Africa were established in their area for a very long time, as long as 90,000 years, and their lands were, along with Australia and the southern tip of South America the closest territory to Antarctica. But it's still an incredibly long way away, and unlike the Austro-Asians or the later Lapita/Polynesia/Mala there was no apparent tradition of even coastal boating. Vanishingly unlikely

Phoenicians - Long shots. The Phoenicians were a mediteranean sailing culture who are established to have explored a fair bit of Africa's coast. Some have them just about circumnavigating Africa, though that's unlikely. Also vetted about, is the possibility that the Phoenicians may have made it to the New World. Based on this sort of speculation, and the certainty that the Phoenicians had crossed into the southern hemisphere, there's a tiny chance that some Phoenicians may have made it all the way to green Antarctica, and an even tinier chance they may have succeeded there.

Romans - like the Phoenicians, but much more unlikely.

Arabs - Medieval Arabs were some of the greatest sailors and traded through the Indian Ocean. Unfortunately, they were coast huggers. So their chances are remote.

Fuegans - the inhabitants of Tierra del Fueggo. Likelihood, remote. But given how inhospitable Fueggo is, they might have the best odds of surviving.

Vikings - Great seafarers, explorers and discoverers of unknown lands, never ventured into the tropics. I figured I had to include them, but the notion of Vikings getting to Antarctica and setting up shop is even more unsually ASB.

Other ASB candidates - Incans, Egyptians, Celts, Greeks, Chinese...

Possible ASB scenario - hive monkeys evolve up to something comparable to human civilization or intelligence.

Most likely discoverers and eventual colonizers - The Renaissance Europeans who actually discovered the place.

Anyway, thats how I see it. Left alone, I'd probably go with Europeans. But if anyone wants to make an argument or sketch out a history for one of the other, or some new group, welcome aboard.