The fruits of migration

As chance would have it, following my recent speculative foray into the possible connection between language and crop diversity, an essay by the great Andrea Wulf 1 has just appeared that tells the story of how a remarkable German naturalist used breadfruit and linguistics to work out Polynesian migration patterns long before DNA or archaeology could confirm them.

George Forster sailed with his father aboard the HMS Resolution on Cook’s second voyage (1772-1775) and encountered breadfruit across the South Pacific. He noticed that the trees were seedless and could only be propagated by root cuttings. And also that there didn’t seem to be wild breadfruit trees anywhere in the islands. That meant every tree he saw, and there were many of them, had been deliberately planted by people.

Digging through the university library back in Göttingen, Forster later found that wild, seeded breadfruit with little flesh do exist, but in Southeast Asia. If the Pacific islands only had the improved, seedless types, he reasoned, they must have been carried there by people. That was proof both of sophisticated Polynesian plant management and of a migration route running from Southeast Asia eastward across the Pacific.

Forster combined this with careful attention to language. He deduced that most Pacific languages he encountered were dialects of a single root language, with small, systematic sound shifts. He and his father also charted how the presence of Malay loanwords decreased the farther east an island was located, which suggested that islands closer to Southeast Asia — the home of Malay — were settled earlier.

Where his fellow naturalist Joseph Banks saw the breadfruit purely as an economic resource (later lobbying to transplant it to the West Indies to feed enslaved plantation workers, hence HMS Bounty and all that), Forster saw it as historical and ethnographic evidence. That’s a strikingly different, more humanistic and — to me at least — more appealing way of reading a plant.

Wulf then jumps forward to modern archaeology and genetics, which broadly confirm Forster’s reconstruction. There was an initial human population in the region of Papua New Guinea dating back 45,000 years. This was followed by a second, Austronesian-speaking wave migrating out of Taiwan and thereabouts around 3,500 years ago. They travelled by the stars in “outrigger or double-hulled canoes loaded with hogs, chickens, root vegetables, coconuts, bananas, and breadfruit seedlings.” And they mixed with the descendants of the earlier wave through Melanesia. Their own descendants eventually reached Fiji, Samoa, Tonga, and, much later, Tahiti, Hawaii, Easter Island and New Zealand.

The essay closes by tying this to Tongan historian Epeli Hau’ofa’s idea of “Oceania” — the Pacific not as scattered, isolated islands, lost in a vast ocean, but as one interconnected “sea of islands.” Exactly what Forster intuited two centuries before it became conventional wisdom.

We’ve blogged a lot about breadfruit over the years. Check out the archive. And in particular listen to the recently-retired Dr Diane Ragone describe her 40-year journey to understand this remarkable tree.

A Babel of agrobiodiversity

The rise and fall of language diversity through the Holocene” by Blasi, Hamilton, Gray & Bowern, published in Science last month, does something I really love. It complicates a standard narrative.

The received story of language diversity is that it has been declining steadily for centuries, largely driven by colonialism and globalization. But direct evidence is scarce and recent: writing only reliably takes us back about 6,000 years. So the team combined ethnographic data from 171 hunter-gatherer and fisher societies, paleodemographic estimates of global population, and statistical and social-computational modelling to reconstruct plausible trajectories of global language diversity over the 12,000 years of the Holocene, which began after the last major ice age, triggering the birth of agriculture.

At the beginning of this period, they estimate there were roughly 4,500–6,200 languages. That’s actually fewer than the roughly 7,500 languages spoken today. Language diversity then increased through most of the Holocene, driven by the population growth engendered by agriculture, reaching a peak between about 1,000 and 3,000 years ago, when the models suggest that tens of thousands of languages may have existed. That’s an order of magnitude more than today.

Then came a major collapse. The authors argue that the decline in linguistic diversity began with the expansion of large states and empires, long before European colonialism. Expanding populations and their languages, cultures and institutions displaced smaller ones. Today’s languages are therefore “survivors of a massive and highly selective historical bottleneck.” They persist because the populations speaking them expanded. Extinction, the authors argue, has shaped linguistic and cultural diversity far more — and for longer — than we have appreciated.

Now, there are obvious caveats. The authors are modelling linguistic diversity, not measuring it. Their estimates depend on heroic assumptions about early ethnolinguistic group sizes, global population and the relationship between population and language number. Regional histories could have been very different, and the model can’t reconstruct individual episodes of extinction caused by war, disease or environmental change.

But the paper provides a provocative template for thinking about diversity more generally. It suggests that population growth can initially generate diversity; but expanding societies can subsequently erase it through homogenization.

And that makes me wonder about agricultural biodiversity. You saw that coming, I’m sure.

I’m not suggesting that crop diversity followed the same pattern as language diversity through the Holocene. We simply don’t have the evidence to say that, though it’s an intriguing thought. But could we borrow the methodology? Could we reconstruct plausible trajectories of crop or agricultural-system diversity from fragmentary archaeological, ethnobotanical, genetic and demographic evidence?

Rather than assuming that agricultural diversity was vast and stable in the distant past, happy in its Vavilovian centres, and has been declining recently, perhaps we might end up complicating the familiar genetic erosion narrative too. That would be worthwhile. And fun.

The accessions in Spain fall mainly everywhere

My ex-colleagues at the Crop Trust have a very nice animation on the Genesys blog-type thing showing the progress of landrace collecting around the world over the past 125 years.

Do please read the post for the details of how it was done, and some observations on the results.

Here I just wanted to highlight something that has always intrigued me: how did Spain get so heavily collected? It’s really striking how in any global map of collecting localities, Spain looks like a solid carpet, with genebank accessions from practically every nook and cranny. More so than most neighbouring countries, I would say.

Well, it’s a little difficult to be sure because there’s no slider on the animation to take it backwards and forwards at will, but it looks like a burst of collecting first in the 40s, and then some filling in of gaps in the 80s, are responsible for the blanket coverage.

Maybe someone more familiar with the history of germplasm collecting in Spain can explain more.

Brainfood: Avocado history, Brazil commuity seedbanks, Citizen science, Agroecology double, Indigenous knowledge, Turkish seeds, Swiss biodiversity

Nibbles: Museum of Cider, Aport apple, Rattan genebank, Sri Lanka rice, Saudi coffee landscapes

  1. In the UK, Herefordshire’s Museum of Cider is picking up national recognition for its genebank of heritage apple trees. The BBC’s canonical autumnal apple story comes a little early this year.
  2. Speaking of iconic apples, Kazakhstan is scaling up efforts to bring back the Aport, the giant heirloom that once made Almaty famous. No word of museums, though. Or cider.
  3. Over in the Philippines, Department of Environment and Natural Resources is beefing up its rattan genebank to keep pace with demand, with forest stewards in Bukidnon planting seedlings to match. Furniture makers need genebanks as much as cider makers.
  4. Sri Lanka’s pre-Green Revolution heirloom rice varieties, purana haal, are being eyed for their resilience and disease-management potential. Good thing they’re in the national genebank.
  5. Saudi Arabia’s Jazan terraced coffee farms are turning into rural and ecotourism hotspots, proving not all agrobiodiversity needs to be in a genebank to survive. But it helps.