Category: Genetic diversity

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Linking archaeology and agrobiodiversity

It was probably a silly thing to say. A couple of days ago I briefly mentioned the models that researchers have built, based on present-day genetic data on Europeans, to understand the rate and pattern of human movement into the continent during the Neolithic. And I made the throw-away comment that I wasn’t aware of similar models for crops. I sort of instantly regretted it, and last night did some googling.

At first I thought perhaps I was right after all. I found a recent (2006) paper whose abstract says:

Thus far, no attempts have been made to track the movement of the founder genetic stocks of the first crop plants from their core area based on the genetic structure of living plants.

Further on, though, the authors say they’ve done just that for wheat. And I also found reference to a “Domestication of Europe” project which sought

to determine the extent to which phylogeographical analysis of modern landraces of barley and wheat, combined with examination of ancient DNA in preserved specimens, can reveal genetic information pertaining to the spread and establishment of cereal cultivation from its points of origin in Southwest Asia into and through Europe.

I think the project must have run from 2003-2006. The Glyn Daniel Laboratory for Archaeogenetics at Cambridge was one of the labs involved, and some of the work, and other related research projects, is described on its website.

So there are people out there trying to link up the archaeology and human genetics of agricultural spread in Europe with the genetics of crops and livestock. Is it too early for a Grand Synthesis?

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The spread of agriculture into Europe

You may recall a post a few days back on how domestic pig keeping spread into Europe. Well, Razib over at Gene Expression, a genetics blog, has a post today which includes a map of the spread of agriculture north and west from the Middle East. He points out that current thinking is that either the practice of agriculture did the spreading (cultural diffusion), or people themselves (demic diffusion) — or both. Both was what the pig work implied, of course. Human genetic studies suggest that Neolithic people have made a fairly low (maybe 20%) contribution to European ancestry, and Razib summarizes the current debate about whether that therefore refutes the hypothesis that movement of people was involved in the spread of agriculture, as well as that of ideas. Bottom line: it probably doesn’t.

He also links to a recent paper that calculates a figure for the rate of movement ((Tracing the Origin and Spread of Agriculture in Europe. Pinhasi R, Fort J, Ammerman AJ. 2005. PLoS Biology Vol. 3, No. 12. doi:10.1371/journal.pbio.0030410)): 1 km/year, give or take. That was arrived at by interpolating radiocarbon dates of Neolithic archaeological sites across Europe, and it fits very well with the results of models using human genetic data. ((As far as I’m aware, however, nobody’s done anything similar with crops.)) An interesting way to think about that speed of movement is that it is roughly a one-day walk per generation.

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Home is where you make it

Professor Roy Ellen, the project director, said: “This project aims to better understand the levels of agrobiodiversity found in home gardens – that is those gardens intimately linked to individual households. For example, we want to know where seed and other plant material comes from, whether it is purchased or obtained informally, who gives and receives it; who receives vegetable produce, and the economic scale of such exchanges. We wish to learn how people learn to become good home gardeners. Whilst biological diversity in itself is important, so are the skills and knowledge that maintain it.”

If you were a reasonably active member of this community and you read the above quotation you might just possibly think, “Ah. Another project to explore the value of agricultural biodiversity and the social networks that support it in some far-flung corner of the developing world. Nepal, maybe, or Burkina Faso.”

But you would be wrong. For the quote comes from an announcement of a project to study home gardens in that most English of settings, Kent. ((I’m giving it more space than Luigi’s original nibble, because I think it is worth it.)) This is exactly the sort of thing I think is sorely needed to forge links among people worldwide. I’ve not been able to find out that much more about the project, although it seems that at least some people at the University of Kent are admirably qualified. And both the Eden Project and the Royal Botanic Gardens, Kew, “will help with the dissemination of the project output”. I hope that means that they will draw the connections to home gardeners everywhere.

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More rice terrace wonders

Also at Yunnan Agricultural University I got a brief glimpse of some absolutely fascinating research from the Yuanyang rice terraces, which rival those of Banaue in age and extent. Professor Wang Yunyue, who just happens to be the wife of Professor Zhu, has been studying the agriculture of the Hani people who have cultivated the terraces for at least 1300 years. Modern hybrids have been introduced from time to time, but the Hani always abandon them after a couple of years, usually because they are no longer resistant to the diseases they were brought in to combat. Instead, the Hani continue to grow their traditional landraces.

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Feet of clay

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That’s another one to tick off the life list. Above you see Zhu Youyong, who describes himself as a farmer. He happens also to be Distinguished Professor Zhu, President of Yunnan Agricultural College and a hero of mine.

Zhu’s name is associated with a method of growing rice that delivers higher, more stable yields with lower inputs of fungicides and a more stable harvest from year to year. Not bad for an amazingly simple idea. The problem is that traditional landraces of sticky rice, which farmers like to grow and to eat, are susceptible to fungal disease. They also have a nasty tendency to fall over, or lodge, especially when they are carrying a bountiful load of seed. Modern hybrids are disease resistant, and high-yielding, but the taste is not much to write home about. Yields are high, but prices are low. To grow the tasty traditional landraces, farmers need to be able to afford fungicides and they need to be able to overcome their tendency to lodge.

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