Who Introduced the Sweet Potato into PNG?

How did the sweet potato or kaukau (Ipomoea batatas) arrive to be in PNG?

I asked myself that question as I was reading Jared Diamond’s ambitious Pulitzer Prize winning book Guns, Germs and Steel. For those who don’t know the book, Diamond essentially argues that Eurasian civilization and consequently domination of the world is not so much a product of ingenuity, but of opportunity and necessity – of being in the right place at the right time.

Diamond goes on to explain why indigenous crops from different parts of the globe were not as equally productive, particularly crops in the New Guinea highlands – one of the few places in the world where food production arose independently. While making the point that the limits on indigenous food production in New Guinea had nothing to do with New Guinea peoples and everything to do with the New Guinea biota and environment, Diamond states that:

Finally, in former times New Guinea’s available root crops were limiting for calories as well as protein, because they do not grow well at high elevations where many New Guineans live today. Many centuries ago, however, a new root crop of ultimately South American origin, the sweet potato, reached New Guinea, probably by way of the Philippines, where it had been introduced by Spaniards” (Page 149).

It is a well known and generally accepted fact that the Spanish did introduce the sweet potato to the Philippines directly from its native South American home. The first Spaniards to reach the Philippines arrived in 1521, so according to Diamond, sweet potato (kaukau in Tok Pisin) has only been in PNG for a possible 487 years (inclusive of the time it would take the plant to move from the Philippines to PNG) – a claim I find difficult to accept.

There are a variety of contradictory theories regarding the introduction of sweet potato into New Guinea. Some claim it to be introduced from Indonesia, from the Malayan Archipelago, from the Solomons, from Polynesia, and via Europeans, via Melanesians, and/or via Polynesians.

Diamond’s claim is hard to accept because of a number of reasons:

1) The highly developed technology for growing kaukau suggests that it needed more than 400 years to evolve. It is difficult to believe that the systems developed for the cultivation of kaukau managed to be diffused among the hundreds of tribes in both coastal and interior PNG within 400 years. Tribal hostilities, geographical topography, and language disparities all posed serious barriers to the introduction and diffusion of the plant so extensively within PNG.

2) There is a cultural element to the existence of kaukau within the social constructs of those societies that are familiar with the plant. For example, many peoples within the Central Province of PNG have quite complex and elaborate myths/stories about the origin of kaukau and place importance on the plant in various ritual systems. The timeframe of 400 years is nowhere enough to warrant the fixation some PNG tribes have with the crop – it needed a longer timeframe for these intimate connections to be developed.

3) One of the most damning pieces of evidence is the fact that the inhabitants of Wantoat Valley of the Huon Gulf have the greatest differentiation of the plant recognizing forty to fifty varieties of kaukau. It is impossible that the Spanish introduced sweet potato in the Philippines managed to biologically evolve into fifty separate varieties within 400 years.

4) The plant is known in the Philippines as camote, the Mexican name for sweet potato. The Portuguese spread the Arawak term (batata) and the Spanish spread the Nahuatl one (camote). All throughout south east asia up to China and down to Malaysia, the plant is known by some name that is related to the two above. However, both names are totally absent in PNG and to complicate matters more, most New Guinea tribes have their own name for kaukau in their Tok Ples.

It is important to explain here that at the time the Spaniards introduced the plant to the Philippines and consequently its dispersion to the rest of South East Asia, China, and Micronesia, the plant had already been well developed in Polynesia. How it arrived in Polynesia before Magellan circumnavigated the world is still disputed, but when the first explorers reached New Zealand, Hawaii, and Easter Island – the sweet potato was present and played a dominant role among the indigenous peoples. Melanesia and particularly New Guinea provide an enigma to the introduction and dispersion of the sweet potato.

So, who introduced kaukau to PNG and how was it introduced?

To understand the answer further, I have included a map (Figure 1) that shows the distribution of kaukau cultivation in New Guinea.

The distribution of sweet potato cultivation in New Guinea

Figure 1: The distribution of sweet potato cultivation in New Guinea

As you can see, there are certain ecological conditions where the plant will not grow – and as many Papua New Guineans know, these areas include the sago dominant marshy parts of West and East Sepik and swampy parts of Western Province. You will note that the kaukau’s stronghold lies in the highland provinces of PNG, Morobe Province, and smaller parts of Madang and Gulf Provinces.

Figure 2 illustrates the distribution of Austronesian and non-Austronesian (Papuan) languages in PNG. As can be seen, Austronesian (Melanesian) languages dominate much of New Britain and the coastal Huon Gulf region of Morobe Province.

The distribution of Austronesian (Melanesian) and Non-Austronesian (Papuan) in New Guinea and in New Britain of the Bismarck Archipelago

Figure 2: The distribution of Austronesian (Melanesian) and Non-Austronesian (Papuan) in New Guinea and in New Britain of the Bismarck Archipelago

The movement of Melanesian-speaking people into the Markham Valley coupled with the localisation of other Melanesian groups along the coast strongly suggests the Markham Valley as the avenue of entrance into the highlands via Melanesian peoples. Figure 3 indicates the proposed route of kaukau into New Guinea via Melanesians and then its spread through the island.

And how was kaukau introduced? Most likely bird of paradise hunters and traders from the Solomons introduced the plant to New Guinea.

The proposed avenue of entrance of the sweet potato into New Guinea from the Bismark Archipelago area, and the proposed routes of its spread to the northeast and southwest area of the Markham Valley region.

Figure 3: The proposed avenue of entrance of the sweet potato into New Guinea from the Bismark Archipelago area, and the proposed routes of its spread to the northeast and southwest area of the Markham Valley region.

Combined linguistic, archaeological, and historical data point to a pre-Magellan spread initially somewhere in the Samoa group and from there to all points of the Polynesian triangle. The plant then moved to parts of Melanesia via Polynesians and from Melanesia to the Markham Valley area of New Guinea. This transference into New Guinea was probably done by Melanesians – very likely both bird of paradise hunters as well as migrants settling on the coast of southeastern New Guinea. From the coast it spread into the highlands through the Markham Valley first by Melanesians and then by Papuan people.

~ by Tavurvur on November 3, 2008.

5 Responses to “Who Introduced the Sweet Potato into PNG?”

  1. Yet again you amaze me! Great write up…I’ve read Diamonds book, but I must admit I simply glossed over that Kaukau theory…

  2. Thanks Emmanuel 🙂

    I’ve got a couple small bones to pick with that book – I chose the kaukau because its about what matters most to me – PNG.

    Diamond wrote an article in the New Yorker (I think) not too long ago which really antagonised me. I’ll see if I can find it again and I’ll post the link up here. It was about vengeance killings in the Highlands.

    See what you guys think about it.

  3. Latest claims seem to indicate a MesoAmerican origin by non human dispersal.

    Click to access 39historic.pdf


  4. Hi Jamie,

    Thanks for your comment – I appreciate it.

    I will read the links you provided.



  5. great stuff..I also read Jared Diamonds book and have been very much interested in sugar cane being native to PNG whilst kaukau originating from South America. There are oral histories from certain parts of PNG (ie; Central Mekeo region, Gulf – East Kerema region and Milne Bay) that relate to some people who arrived there well before the Europeans. I have been tracing the story of kaukau and the sugar for some time and strongly believe it was the Peru Incans led by Topa Inca Yupanqui who was responsible for introducing the sweet potatoe in PNG and other South Pacific islands.


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