Wednesday 27 June 2012

Pollen from potshards, and what it can tell us about the ancient climate of northwest China.

Pollen is extremely useful to archaeologists and palaeontologists. It is resilient both and distinctive, and plants produce it in large amounts, and scatter it freely in the environment. Scientists who study pollen, called palynologists, are able to use pollen to date ancient sediments and to reconstruct the vegetation, and therefore climate, of ancient sites. Recently archaeologists have discovered pollen can be extracted from some ancient pottery, if this was incompletely fired, i.e. not fired at a high temperature or for a long period of time.

In a paper published in the journal PLoS One on 25 June 2012, a team of scientists led by Yi-Feng Yao of the State Key Laboratory of Systematic and Evolutionary Botany at the Institute of Botany at the Chinese Academy of Sciences, describe the recovery of pollen from potshards from the Yanghai Tombs of Turpan in Xinjiang Province, western China, and the implications for the climate in the time when the tombs were excavated.

The Yaghai Tombs are located in the Flaming Mountains in eastern Xinjiang province, and are between 2000 and 3000 years old. The area is now extremely arid, with settled farming populations inhabiting scattered oases. However at the time the tombs were dug it is thought the area had a more temperate climate. 

The location of the Yanghai Tombs. (A) Map showing the location of Xinjiang Province in China. (B) Map showing the location of the Flaming Mountains within Xinjiang Province. (C) Satellite Image of the Flaming Mountains and surrounding area, showing the location of the Yanghai Tombs. Yao et al. (2012).

The Yanghai Tombs were laid down by by the Subeixi Culture, and contain large amounts of pottery, as well as other goods. They have provided useful botanical material previously, in the form of plant materials buried as grave goods. This has been fairly well publicized due to the large amount of cannabis present, but also included food crops such as grapes, melons, apricots etc.

Pottery goods from the Yanghai Tombs. (1) Single-handled jar with waves. (2) Single-handled pot with folded lines. (3) Single-handled cup with arcuate sculpture. (4) Single-handled cup with whirlpools. (5) Single-handled jar. (6) Single-handled jar with reticulations. (7) Single-handled jar with triangles. (8) Single-handled pot with serrate patterns. (9) Single-handled cup with flame-like patterns. (10) Single-handled jar with waves. (11) Pottery basin. (12) Pottery bowl with four legs. Photographed by Yong-Bing Zhang. Yao et al. (2012).

Yao et al. extracted pollen from potshards (broken pottery) from two tombs at Yanghai, both roughly 2700 years old. The pottery from the first tomb appeared to have been fired at to high a temperature for to long for much pollen to have been preserved, however a good amount of pollen was recovered from pottery from the second tomb. The first tomb yielded pollen from Wormwood, Lilies, Elms, Buckwheat, Legumes, Mulberries and grasses, the second pollen from Clubmoss, Ephedra, Artemesia, Elms, Goosefoot, Asters, Beeches and Gentians, with Goosefoot and Elm being the most abundant.

By combining the data from the pollen with that from the previously gathered plant remains, Yao et al. were able to make an interpretation of the vegetative cover at Yanghai 2700 years ago. They conclude that the overall climate of the Flaming Mountains was still arid in this period, but that the tombs were dug close to a marshy oasis surrounded by grasslands and coniferous woodland.

See also The origin of domestic dogsDating the Chauvet Cave artWhat Nitrogen tells us about the diet of MammothsWhat a 4.6 million-year-old Three Toed Horse can tell us about the climate of Mid Pliocene Tibet and Trying to find Peking Man.

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