Global cooling event 4,200 years ago spurred rice’s evolution, spread across Asia

Posted: May 15, 2020 by oldbrew in climate, History, research
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Honghe Hani Rice Terraces in Yunnan Province, China [image credit: Wikipedia]


A look back to an earlier era of dramatic climate change, long before anyone had time to obsess about atmospheric trace gases.
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A major global cooling event that occurred 4,200 years ago may have led to the evolution of new rice varieties and the spread of rice into both northern and southern Asia, an international team of researchers has found.

Their study, published in Nature Plants and led by the NYU Center for Genomics and Systems Biology, uses a multidisciplinary approach to reconstruct the history of rice and trace its migration throughout Asia, says Phys.org.

Rice is one of the most important crops worldwide, a staple for more than half of the global population.

It was first cultivated 9,000 years ago in the Yangtze Valley in China and later spread across East, Southeast, and South Asia, followed by the Middle East, Africa, Europe, and the Americas.

In the process, rice evolved and adapted to different environments, but little is known about the routes, timing, and environmental forces involved in this spread.

In their study, the researchers reconstructed the historical movement of rice across Asia using whole-genome sequences of more than 1,400 varieties of rice—including varieties of japonica and indica, two main subspecies of Asian rice—coupled with geography, archaeology, and historical climate data.

For the first 4,000 years of its history, farming rice was largely confined to China, and japonica was the subspecies grown.

Then, a global cooling event 4,200 years ago—also known as the 4.2k event, which is thought to have had widespread consequences, including the collapse of civilizations from Mesopotamia to China—coincided with japonica rice diversifying into temperate and tropical varieties.

The newly evolved temperate varieties spread in northern China, Korea and Japan, while the tropical varieties and spread to Southeast Asia.

“This abrupt climate change forced plants, including crops, to adapt,” said Rafal M. Gutaker, a postdoctoral associate at the NYU Center for Genomics and Systems Biology and the study’s lead author.

“Our genomic data, as well as paleoclimate modeling by our collaborators, show that the cooling event occurred at the same time as the rise of temperate japonica, which grows in milder regions. This cooling event also may have led to the migration of rice agriculture and farmer communities into Southeast Asia.”

“These findings were then backed up by data from archaeological rice remains excavated in Asia, which also showed that after the 4.2k event, tropical rice migrated south while rice also adapted to northern latitudes as temperate varieties,” said Michael D. Purugganan, the Silver Professor of Biology at NYU, who led the study.

After the global cooling event, tropical japonica rice continued to diversify. It reached islands in Southeast Asia about 2,500 years ago, likely due to extensive trade networks and the movement of goods and peoples in the region—a finding also supported by archeological data.

Full article here.
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Related: Weedy rice is unintended legacy of Green Revolution (March 2020)
A new global study reveals the extent to which high-yielding rice varieties favored in the decades since the “Green Revolution” have a propensity to go feral, turning a staple food crop into a weedy scourge.

Comments
  1. […] Tallbloke’s Talkshop: Global cooling event 4,200 years ago spurred rice’s evolution, spread across Asia […]

  2. glenndc says:

    Interesting. This coincides with Dr Barbara Bell’s work from the 70s, Harvard Observatory Astronomer and Egyptologyst about the dark ages of Egypt, ca 2,200 BC. The meticulously maintained Pharaohnic Nile flood records going back to 6 KYA undergird and substantiate her hypothesis. Read here

    http://www dot gizapyramids dot org/pdf_library/bell_aja_75_1971.pdf

    And at Chiefio’s site 7 years ago

    https://chiefio dot wordpress dot com/2013/04/28/egyptian-dark-ages/

    Your article about SE Asia further globalizes and substantiates her findings and hypotheses.

  3. JB says:

    Seems to coincide with the onset of the cooling period beginning ca 2100BCE.

  4. ivan says:

    The related item at the end of the article caused me to chuckle because the greens appear to be unable to get anything right. It is also sad because of the green stupidity a staple food for many may be harder to grow and harvest.

    If the greens stopped poking themselves in where they are not wanted/needed the world would be a better richer place and we wouldn’t be bombarded with fake science.

  5. oldmanK says:

    Full pdf here: https://www.biorxiv.org/content/10.1101/748178v1.full.pdf

    The date 4k2 BP (or 2k2bce) is when the impact of change began to leave traces in many proxies. It takes decades to a few centuries for a trace to appear as a distinct change in a cultivar. But the abrupt event that started it occurred earlier, at 2345bce (see https://tallbloke.wordpress.com/2014/12/24/dodwells-surprising-study-of-the-obliquity-of-the-ecliptic/ )

    Such change cooled equatorial regions and warmed higher latitudes further above the tropics, thus widening the band of latitudes that would allow cereal development – from what was around Lat 15 – 30deg (it seems). See page 22 of the pdf for the spread of the various varieties as these were adapted according to region’s new/changed climate. One is likely to find the same developments in corn/wheat and barley in Europe and the Near east.

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