Allan,
It took me a while to dig up some references about sorghum in Asia. The gist of these and others is that, while sorghum (and two kind of millets) show up in India at an early date, they were transported over land or at most short sea hops and not by Austronesians.

Kirk, W. 1962 “The N.E. Monsoon and Some Aspects of African History,”
The Journal of African History[.b], 3(2): 263-267

p. 266 “In the period prior to the undertaking of long trans-oceanic voyages these two peripheral transition zones were of the greatest significance to cultural exchange. Both, for example, appear to have played a vital part in the diffusion of early agricultural ideas. So important was the Ethiopian area in this respect that Vavilov named it as one of his prime areas for plant domestication, and its contribution has been emphasized more recently by Sauer. Its true function, however, is increasingly seen as a corridor-part of the so-called Sabaean Lane-rather than as an area of initiation. African plants of the Sudan complex, such as sorghums, sesame, pearl millet, cow pea (Vigna unguiculata), and Coleus dysentericus, appear to have reached India by this route and in return various legumes, cucumber, hemp,
mango, etc., entered Africa. Asiatic fauna, including Zebu cattle and the associated 'cattle complex', seem to have followed the same route, and Arkell et al. have stressed the Indian element in N.E. African cultural development. Similarities in 'megalithic' structures and common cosmological ideas of settlement planning may point in the same direction.”
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[www.plantsciences.ucdavis.edu]
This is a course outline at U.C. Davis in 2010.

Look at the outline of diffusion of African plants

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Kimber, C. T. 2000 “Origins of Domesticated Sorghum and its Early Diffusion to Indian and China, In Smith, C. W and R. A. Frederiksen, eds. Sorghum: Origin, History, Technology, and Production, pp. 3-98 NY: Wiley

Google books does not allow copying so that this very informative map is not available. What follows is my description of the arrows indicating transmission of sorghum.

p. 15 Figure 1.1.3 Early human migrations and associated diffusion of S. bicolor races

>3000 B.C. Sind-Punjab via Red Sea ports (across Arabian Peninsula Yemen Sabaean Lane)

2000 B.C. India from east coast ports of Africa (?) [question mark]

c. 2000 B.C. Durra to northern India

2000 B.C. from central Africa to Guinea and Mande core Niger bend


p. 50 “Doggett (1988) reports that imports from east Africa and Somalia came via Aden, citing early sea trade between the Kulli of South Baluchistan and Early Dynastic Sumer around 2800 B.C.. . .
Recent work by Edens and Wilkinson (1998) asserts definitely that the high plateau of Yemen was an early focus for a developed Bronze Age complex society. Its economy relied upon terraced rain-fed and runoff agriculture. These peoples on the fringes of the Arabian Desert are, according to these investigators, the possible precursors of Sabaean literate civilization. they have been traced back between 3600 ad 2800 B.P.. . perhaps earlier. These Bronze Age finds link the Yemen Neolithic with the Iron Age settlements dated to 7930+/- 115 B.C. The authors go on to say that the Bronze Age show some links with the southern Levant but show “equal or stronger linkages with the Horn of Africa across the Red Sea” (Edens and Wilkinson, 1998). That is, links with Punt and with Ethiopia are demonstrated by the archaeology. Fattovich (1997) maintains that traffic across the mouth of the Red Sea may well go back to the early Iron Age. He may be conservative. This trade route is in addition to the trade routes traveled by incense merchants to the north across the Arabian Peninsula.
Based on historical sources, Pickersgill (1983) suggests that the Sabaean Lane was probably functioning long before the second millennium B.C. (Figure 1.1.8). This is the classic route Doggett uses in his discussion of introductions to northern India (Doggett, 1988). There were, however, other routes to northern India from other directions. These may have had some traffic that affected the diffusion of sorghum to and form India. The great Silk Road across inner Asia is well known, which of its various tracks in use depending on the access permitted by various local warlords (Lerner, 1996) (Figure 1.1.8). It is well known that there were two major ‘silk rotes’ to India. One came south from the inner Asia route dropping down from Kashgar that lies just west of the Tarim Basin, where travelers refreshed themselves for the journey for the west (Warmington, 1974).
. . .
p. 52 Speculating sorghum may have come to the southern part of India, landing at the ports on the Malabar coast and thence coasting north via the Arabian Sea (Scheuring, 1979; Harlan, 1972a) (Figure 1.13). Alternatively, sorghum might have been traded over the Western Ghats onto the plateau. Archaeological investigations in peninsular India have established the presence of cultures by 3000 B.C. In an archaeological site at both Hallur and Paiyampalli, finger millet, also called ragi (Eleusina abyssinica), is in evidencee about 1800 B.C. (Allchin, 1969) (Figure 1.1.8). Niger (Guizotia abyssinica). a crop of Ethiopia, has local names in many Indian languages, which suggests some age in India. Porteres and Barrau (1985) suggested sorghum as a prime example of an African plant going to Asia. they assert that S, bicolor (derived from a different process from Harlan, i.e. by crossing S. aethiopicum and S. Sudanense) may be linked to S. dochna Snowden of India, Arabia, and Burma (Kajale, 1991). The archaeobotanical record of African crops in the Deccan region, particularly support such a thesis.
In the latest authoritative discussion of crop plants in the Indian subcontinent, which takes as its emphasis sites north of the Deccan Plateau, Meadow (1996) points out that the major introductions of the second period of plant introduction to India were African plants. As witnessed by the archaeological record, the introductions were first, finger millet, followed by sorghum, and then by pearl millet. This diffusion took about 1000 years..”

I’ll return now to looking at Austronesians, Maagascar and bananas, Hopefully, I’ll get to Egyptian mummies and cocaine- which will tie in to the current discussion about copper.