When and where was rice domesticated?

ResearchBlogging.orgA paper by Dorian Fuller and his colleagues in this week’s Science sets out three kinds of evidence that help to pinpoint the time and place of rice domestication in eastern China. ((Fuller, D., Qin, L., Zheng, Y., Zhao, Z., Chen, X., Hosoya, L., & Sun, G. (2009). The Domestication Process and Domestication Rate in Rice: Spikelet Bases from the Lower Yangtze Science, 323 (5921), 1607-1610 DOI: 10.1126/science.1166605)) The site is Tianluoshan, just north of the current town of Hemudu on Hangzhou Bay. The water table is very high, which has preserved botanical remains and charred remains, as well as artefacts. Among those remains are more than 35,000 fragments that show how the foodways of the people changed.

In the oldest segment, reliably dated to 4900 years BCE, acorns and water chestnuts (Trapa spp) predominate, with a few other gathered species, notably foxnuts (Euryale ferox). ((A new one on me, related to water lilies. Anyone outside Asia growing it?)). Rice is about 8% of the remains.

Three hundred years later, rice has increased to 24% of the remains, with an equally large increase in the remains of weeds typical of rice paddies.

SEM of wild rice spikelet base
SEM of wild rice spikelet base © Science/AAAS
Over the same 300-year period the nature of the rice remains change too. Microscopic analysis of the base of the rice spikelets, which attach the grain to the stalk, can reveal whether the plant was wild or domesticated, and whether the rice grain was immature (associated with the harvest of wild rice.) Fuller and colleagues examined 2641 spikelet bases and put them into one of these three categories. Domesticated rice increases from 27% to 39% of the total over the 300 years.

©Science/AAAS
©Science/AAAS

Domesticated, it should be noted, is not the same as cultivated. Domesticated types usually have a mutation that keeps the seed attached to the stalk. These non-shattering genes make the domesticated plant dependent on people to spread the seeds, and would be automatically selected for in the normal course of cultivation. As the authors note: “This trend toward an increasing proportion of domesticated types though time implies that rice was under cultivation at this time and that domestication traits were under selection.”

The paper offers clear evidence of rice cultivation and domestication 6500 years ago, but what does it say about the great japonica-indica divide? There are two views; that the two types were domesticated entirely independently, or that there was a single domestication event (selection of the non-shattering gene) which then found its way from japonica types to indica types, perhaps by crossing with wild varieties.

Fuller et al. do not treat this topic at length — that’s not what the paper is about, and Science does not allow for much discussion. I asked Fuller directly, and he said that he thinks “there is a good case archaeologically (and genetically) to be made for a separate origin in the middle Ganges”. So people there independently started to manage wild rice and to cultivate it, and then full domestication got under way around 1900 BCE, with the arrival from China of japonica types and the techniques to grow rice more effectively. He was kind enough to send another paper ((Fuller, D., & Qin, L. (2009). Water management and labour in the origins and dispersal of Asian rice. World Archaeology, 41 (1), 88-111 DOI: 10.1080/00438240802668321
And that looks like an amazingly interesting volume.)) which sets out the ideas in considerably more detail and throws fascinating light on the whole question of the cultural and social organisation needed to grow rice effectively. A parting thought from that:

We suggest that the spread of rice, which has played an important role in models of Neolithic population dispersal in Southeast Asia, may have been triggered by the development of more intensive management systems and thus have required certain social changes towards hierarchical societies rather than just rice cultivation per se.

Forced penning in the Sahara

Mathilda had a post a few days ago which caught my eye, but I forgot to nibble it. Better late than never. She discusses a recent paper reporting on the archaeological excavation of Uan Afuda and other Early Holocene sites of the Acacus mountains, in the Libyan Sahara, and in particular the layers of animal dung that excavations uncovered. The paper suggests that these “dung layers are related to a forced penning of a ruminant, very likely Barbary sheep (Ammotragus lervia),” and that this is evidence of delayed use of resources designed to cope with lean periods. Mathilda goes on to hypothesize that cattle domestication keeping ((See comment from Mathilda.)) may have started in the Sahara — before the growing of crops — in a similar way.

The spread of the ass

Great find by Mathilda: “The history and spread of donkeys in Africa,” by Roger Blench. It’s from the book Donkeys, people and development, edited by Paul Starkey and Denis Fielding. That came out of a 2004 Animal Traction Network for Eastern and Southern Africa workshop. There’s lots of other interesting stuff on the network’s site, including a donkey bibliography.

In brief:

  • domesticated probably in Egypt/Nubia at the beginning of the Neolithic in Africa, 6,500 years ago
  • but perhaps several times in regions of its former range no longer represented by its present-day distribution
  • expansion paralleled that of cultivated sorghum

LATER: And a thousand year later, on another continent, it’s the horse’s turn.

Agrobiodiversity in trouble in Cameroon

Ivo Arrey Mbongaya of the African Centre for Community and Development in Cameroon has a blog on the Eldis Community and has recently discussed threats to two different sorts of agricultural biodiversity in his country. Apparently, goat rearing is in decline, because of the disappearance of grazing land, harsh policies about strays and the lack of veterinary services. He doesn’t say if a local breed is involved, however, and does make reference to “efforts by Heifer Cameroon to distribute cheap animals.”

Also in trouble is “eru,” or Gnetum africanum, a shrub whose leaves are consumed as a green vegetable. Unsustainable harvesting and land use changes are taking their toll, and Ivo recommends taking the plant into domestication.There’s been some work on that by ICRAF and others.