New research on three archaeological sites of the famed Indus Valley civilization (3000-1500 BC) in north-west India has revealed that domesticated rice farming in South Asia began far earlier than previously believed, and may have developed in tandem with — rather than as a result of — rice domestication in China.

Evidence for very early rice use has been known from the site of Lahuradewa in the central Ganges basin, but it has long been thought that domesticated rice agriculture didn’t reach South Asia until towards the end of the Indus era, when the wetland rice arrived from China around 2000 BC.

A research team led by University of Cambridge archaeologists found evidence of domesticated rice in South Asia as much as 430 years earlier.

The team’s findings, published in the Journal of Archaeological Science and the journal Antiquity, also confirm that Indus farmers were the earliest people to use multi-cropping strategies across both seasons, growing foods during summer (rice, millets and beans) and winter (wheat, barley and pulses), which required different watering regimes.

“The nature and timing of rice domestication and the development of rice cultivation in South Asia is much debated,” the authors said.

“In northern South Asia there is presently a significant gap (about 4,200 years) between earliest evidence for the exploitation of wild rice (Lahuradewa, 6000 BC) and earliest dated evidence for the utilization of fully domesticated rice (Mahagara, 1800 BC).”

“The Indus Valley civilization, also known as the Harappan civilization, developed and declined during the intervening period, and there has been debate about whether rice was adopted and exploited by Indus populations during this gap.”

The researchers found evidence for an entirely separate domestication process in ancient South Asia, likely based around the wild species Oryza nivara.

“This led to the local development of a mix of ‘wetland’ and ‘dryland’ agriculture of local Oryza sativa indica rice agriculture before the truly ‘wetland’ Chinese rice, Oryza sativa japonica arrived around 2000 BC,” said co-lead author Dr. Jennifer Bates, from the Department of Archaeology and Anthropology at the University of Cambridge.

“While wetland rice is more productive, and took over to a large extent when introduced from China, our findings appear to show there was already a long-held and sustainable culture of rice production in India as a widespread summer addition to the winter cropping during the Indus Valley civilization.”

The team sifted for traces of ancient grains in the remains of several Indus villages within a few miles of the site called Rakhigari: the most recently excavated of the Indus cities that may have maintained a population of some 40,000.

As well as the winter staples of wheat and barley and winter pulses like peas and vetches, the archaeologists found evidence of summer crops: including domesticated rice, but also millet and the tropical beans urad and horsegram, and used radiocarbon dating to provide the first absolute dates for Indus multi-cropping: 2890-2630 BC for millets and winter pulses, 2580-2460 BC for horsegram, and 2430-2140 BC for rice.

Millets are a group of small grain, now most commonly used in birdseed, which the authors describe as “often being used as something to eat when there isn’t much else”.

Urad beans, however, are a relative of the mung bean, often used in popular types of Indian dhal today.

In contrast with evidence from elsewhere in the region, the village sites around Rakhigari reveal that summer crops appear to have been much more popular than the wheats of winter.

“This may have been down to the environmental variation in this part of the former civilization: on the seasonally flooded Ghaggar-Hakra plains where different rainfall patterns and vegetation would have lent themselves to crop diversification – potentially creating local food cultures within individual areas,” the scientists explained.

“This variety of crops may have been transported to the cities. Urban hubs may have served as melting pots for produce from regional growers, as well as meats and spices, and evidence for spices have been found elsewhere in the region.”

“While we don’t yet know what crops were being consumed at Rakhigarhi, it is certainly possible that a sustainable food economy across the Indus zone was achieved through growing a diverse range of crops, with choice being influenced by local conditions,” Dr. Bates said.

“It is also possible that there was trade and exchange in staple crops between populations living in different regions, though this is an idea that remains to be tested”.

“Such a diverse system was probably well suited to mitigating risk from shifts in climate,” said co-lead author Dr. Cameron Petrie, also from the Department of Archaeology and Anthropology at the University of Cambridge.

“It may be that some of today’s farming monocultures could learn from the local crop diversity of the Indus people 4,000 years ago.”

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J. Bates et al. Approaching rice domestication in South Asia: new evidence from Indus settlements in northern India. Journal of Archaeological Science, published online November 21, 2016; doi: 10.1016/j.jas.2016.04.018

C.A. Petrie et al. Feeding ancient cities in South Asia: dating the adoption of rice, millet and tropical pulses in the Indus civilisation. Antiquity 90 (354): 1489-1504; doi: 10.15184/aqy.2016.210

This article is based on a press-release from the University of Cambridge.