And, maybe that is why we only got civilization shortly after the last Neanderthal and Denisovan passed on. That doesn't explain why Australia didn't get it, first, though.
I do not understand how you think multiple human species could impede civilization formation. Can you explain? Also, Australia only left the Stone Age with British colonization. It was plausibly the least technologically advanced inhabited area on Earth at contact.
I only observe the coincidence: while we had Neanderthal about, no moves toward civilization. Any reason would be speculation; maybe they and the Denisovans knew better? If so, they may get the last laugh, as it crashes down around us.
Australia (Sahul, really) was a place with (apparently) no Neanderthal or Denisovans. Whatever would develop only in their absence should have happened there first. Or maybe in Sundaland and points north, before rising seas claimed all of that.
But civilization was well along for millennia before any appreciable "technological advancement", excepting maybe pottery, and things that decay and leave no trace. (Which is most things.)
> Australia (Sahul, really) was a place with (apparently) no Neanderthal or Denisovans.
Things have changed.
> Denisova admixture and the first modern human dispersals into Southeast Asia and Oceania
> It has recently been shown that ancestors of New Guineans and Bougainville Islanders have inherited a proportion of their ancestry from Denisovans, an archaic hominin group from Siberia. However, only a sparse sampling of populations from Southeast Asia and Oceania were analyzed. Here, we quantify Denisova admixture in 33 additional populations from Asia and Oceania. Aboriginal Australians, Near Oceanians, Polynesians, Fijians, east Indonesians, and Mamanwa (a "Negrito" group from the Philippines) have all inherited genetic material from Denisovans, but mainland East Asians, western Indonesians, Jehai (a Negrito group from Malaysia), and Onge (a Negrito group from the Andaman Islands) have not. These results indicate that Denisova gene flow occurred into the common ancestors of New Guineans, Australians, and Mamanwa but not into the ancestors of the Jehai and Onge and suggest that relatives of present-day East Asians were not in Southeast Asia when the Denisova gene flow occurred. Our finding that descendants of the earliest inhabitants of Southeast Asia do not all harbor Denisova admixture is inconsistent with a history in which the Denisova interbreeding occurred in mainland Asia and then spread over Southeast Asia, leading to all its earliest modern human inhabitants. Instead, the data can be most parsimoniously explained if the Denisova gene flow occurred in Southeast Asia itself. Thus, archaic Denisovans must have lived over an extraordinarily broad geographic and ecological range, from Siberia to tropical Asia.
The final sentence suggests there really were Denisovans running around in southeast Asia, way back when. But did they get as far as New Guinea / Australia?
It's a bit hard to imagine a mechanism by which presence of Neanderthals and Denisovans could have so effectively stalled development of the trappings of civilization. But that doesn't mean it didn't happen. We like to think of ourselves as totally badass, but they could have been moreso. Maybe it was unsafe to settle down and build a village where they might swoop in and burn you out. And, our own ancestors could have been doing the same to them. It happened that "we" won.
Another problem is that Neanderthals and Denisovans are not known to have been in Africa. But there could have been any number of other, unknown badass H. species in Africa, besides. Or, maybe, why develop civilization "when there are so many mongongo nuts in the world"? [0]
