Herodotus was right in one sense, that the Etruscans came from the north eastern Mediterranean. I think the idea that the east side of the Mediterranean is foreign or alien to Europe is rather stupid. The Mediterranean Sea linked all the peoples that lived on its shores especially the east side with the north and west. So the Etuscans are not foreign interlopers but just inhabitants of the Mediterranean who moved from one place to another. The old Greeks had their colonies. What would Southern Italy be without those ancient Greek colonies, and their inhabitant’s dna? My most humble opinion is this: The old Greeks and the old Romans (the Italic speakers) were both I.E speaking immigrants who stumbled into their particular peninsulas of Europe like most I.E speakers with their three fold caste system and weapons galore, and proceeded to make themselves native and the natives foreign. In Italy the native Etruscans, the ones who were there before the I.E speakers immigration, became the foreigners. The old Greeks completely removed the Pelasgians. So Herodotus was half right, which for a Greek old or modern, is pretty good going.

On India I suspect that the picture is even more complex than the one you outline, but we await ancient DNA.

Madagascar is apparently very multicultural and xenophile. There was a story awhile back by an Irishman or Irishwoman whose grandfather had left a family in Madagascar, and when she vicited her cousins were happy to see her, partly because they wanted to fill in the gaps in the family genealogy, which went back several generations on the Malagasy side but was sketchy on the Irish side.

http://en.wikipedia.org/wiki/East_Barito_languages

I’ve been to Madagascar – the people show a striking combination of African and Polynesian facial features, and the language is clearly Polynesian with a few Swahili borrowings.

1. Besides the northern European diffusion of the last 500 years or so, during historical time (since about 1000 BC or later) there have been four major long-distance diffusions: Malayo-Polynesians from SE Asia to Madagascar and Easter Island; Turks from NE Asia to the Mediterranean; the Bantu from central Africa to South Africa, and Inuit from Asia to Greenland.

The Malayo-Polynesians travelled by boat, which is one of the ways that long-distance travel can be made easy. The Turks were mounted nomads. The Bantus were technologically and militarily superior to the original inhabitants of S Africa. The Inuit did use boats, but I’m not sure how much of their travel was by water and how much by land.

None of these are refutations of the idea of genetic conservativism. They just show kinds of ways that this kind of diffusion could happen. Nomadism rose after 1000 BC, and even oxcarts are only a couple of millennia older. I don’t know anything about the history of boats, but they seem like a better candidate for early long-distance transportation form. A crude boat can be very easily built. (I have read, incidentally, that there might have been a prehistoric Indian Ocean monsoon trade between Yemen / the Horn of Africa and South India, and that there’s genetic evidence for it. I’ve also seen arguments for prehistoric sea contact between the Americas and Asia, though not in large numbers.) The Bantu migration, with cattle and iron, seems like a late version of the Indo-European migrations.

Absolute distances are not the problem. Beijing and Paris are about 5000 miles apart, and that distance could be negotiated on foot in a few years. The three reasons for not going further that I’ve figured out are motivation (people tend to stop once they’ve found a nice place), an inhospitable, unsupportive environment (without horses the steppe / desert areas of Central Asia are difficult in the best of cases) and human opposition. The last of these is the main argument for conservativism, I think. Once an area is filled up, it’s hard either to cross it or to take it over. But this depends on the relative military efficiencies of the peoples in question. (With human opposition there’s a second contrary factor though. Completely uninhabited areas lack key support necessities like blazed trails, watering places, hostels, etc. and impede travel that way).

There have also been many peoples during recorded history who developed habits of raiding and long distance exploration for no particularly practical reason. In these cases young unmarried men and outcasts go out to seek their fortune without necessarily being very clear what their goal is, conceivably to occupy land if it’s uninhabited or if the people already there can be displaced. Something like this was a factor in Greek, Viking and Turkish migrations. (These raiding groups are often explained by “overpopulation”, but they seldom or never come from genuinely overpopulated areas like Java, Egypt, or Bengal. They’re a consequence of social structures which don’t have places for everyone.)

These are just factors to think of when arguing or explaining the conservativism hypothesis. None is decisive, obviously, but they help make it a more concrete question.

Australia is almost connected to Papua-New Guinea by the Torres Strait islands. The first Aborigines may have come on rafts of fortune, but after the diffusion of reliable seafaring technology, travelling to and from Australia posed no major difficulty.

I’m not sure if the presence of dingos indicates a “major” arrival of new people. Once a few dogs found themselves stranded on the island (perhaps imported by settlers, perhaps left ashore by travellers), they may well have spread quickly on their own due to favourable ecological conditions (open niche FTW!). I understand that dingos are basically feral dogs, in that most of them live independently of humans – and seem to do quite well that way. Also, if dogs had been deliberately introduced as domestic companions, and if their importers had leeft a significant mark on the Australian population, we would expect to see a tradition of keeping and breeding domestic dingos in Australia.

Wiki says: “Linguistic and genetic evidence shows that there has been long-term contact between Australians in the far north and the Austronesian people of modern-day New Guinea and the islands, but that this appears to have been mostly trade with a little intermarriage, as opposed to direct colonisation. “ That’s well enough to allow for a canine takeover.