Diamond replies

Until about 4000 bc, there were no domestic animals, farming, Neolithic tools, or pottery anywhere in Island Southeast Asia and the Pacific, except for Neolithic agriculture in the New Guinea highlands. Around 4000 bc, all of these things appeared in Taiwan and then spread eastwards in archaeologically well-dated stages through the rest of Island Southeast Asia out into Polynesia. Apart from some peoples of New Guinea and some adjacent islands, all those in this vast realm now speak Austronesian languages.

Where did this Austronesian expansion ultimately originate? The archaeological, linguistic, zoological and botanical evidence points overwhelmingly to China, where all of the Austronesians' domestic animals, their pottery styles, their Neolithic tools, their irrigation and fishing technology, and many of their crops and artistic motifs originated. The spread south from China into Mainland Southeast Asia of all four of the other major Southeast Asian language families also correlates with archaeologically attested expansions.

Oppenheimer and Richards downplay this body of evidence, favouring instead an Austronesian origin in Island Southeast Asia itself, specifically in the triangle formed by Taiwan, Sumatra and Timor. But they overlook the fact that modern Austronesian peoples predominantly resemble Asian Mainland peoples in their genes, appearance and physical anthropology, whereas the original inhabitants of Island Southeast Asia (still attested by many relict populations today) resembled modern New Guineans and Aboriginal Australians.

Oppenheimer and Richards cite genetic evidence (for example, the Polynesian marker whose age they calculate), but if genetic evidence is to be useful in reconstructing human population movements, it must be based on many loci and integrated with other types of evidence; calculations of marker ages with extremely wide confidence limits must be viewed with caution. Nobody doubts that Melanesians and other original island peoples did make some minor contribution to the gene pool of the Austronesians as they expanded eastwards through the islands into Polynesia. The Polynesian marker, in combination with other genetic markers and other evidence, should eventually prove useful in illuminating where, when and how, among the hundreds of Austronesian peoples, the Polynesians themselves arose and received that minor contribution. But the marker cannot alter the main conclusions about the Austronesian expansion.