Archaeological Soybean (Glycine max) in East Asia: Does Size Matter?

Gyoung-Ah Lee,Xuexiang Chen,Yuka Sasaki,Li Liu,Gary W Crawford,Lee A Newsom

doi:10.1371/journal.pone.0026720

Gyoung-Ah Lee, Xuexiang Chen + Show 4 more

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https://doi.org/10.1371/journal.pone.0026720

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Abstract

The recently acquired archaeological record for soybean from Japan, China and Korea is shedding light on the context in which this important economic plant became associated with people and was domesticated. This paper examines archaeological (charred) soybean seed size variation to determine what insight can be gained from a comprehensive comparison of 949 specimens from 22 sites. Seed length alone appears to represent seed size change through time, although the length×width×thickness product has the potential to provide better size change resolution. A widespread early association of small seeded soybean is as old as 9000–8600 cal BP in northern China and 7000 cal BP in Japan. Direct AMS radiocarbon dates on charred soybean seeds indicate selection resulted in large seed sizes in Japan by 5000 cal BP (Middle Jomon) and in Korea by 3000 cal BP (Early Mumun). Soybean seeds recovered in China from the Shang through Han periods are similar in length to the large Korean and Japanese specimens, but the overall size of the large Middle and Late Jomon, Early Mumun through Three Kingdom seeds is significantly larger than any of the Chinese specimens. The archaeological record appears to disconfirm the hypothesis of a single domestication of soybean and supports the view informed by recent phyologenetic research that soybean was domesticated in several locations in East Asia.

Highlights

Soybean (Glycine max subsp. max) is the world’s foremost oilseed source and the primary source of protein for chickens and pigs [1] and ranks seventh among world crops by tonnage harvested [2]
Do seed dimensions correlate with chronology? That is, is there evidence of seed size and shape selection over time? Are regional differences in soybean seed size apparent? we evaluate whether the new data inform our understanding of soybean domestication
Soybean seed size tends to increase over time in each region (Figure 9) the chronological pattern of size change differs among the three regions (Figure 10)

Summary

Introduction

Soybean (Glycine max subsp. max) is the world’s foremost oilseed source and the primary source of protein for chickens and pigs [1] and ranks seventh among world crops by tonnage harvested [2]. Despite the importance of the crop to the world economy, how soybean came to be a crucial resource and a domesticated plant has not been enlightened by the archaeological record. In the 2000s two of us [6] documented the first unambiguously domesticated soybean in East Asia from the Daundong and Nam River (Okbang 1/9) sites in South Korea, with two AMS-dates on soybean from ca. This suggested that the hypothesis that soybean was domesticated somewhere in Northeast Asia (potentially in Korea) had merit [7]

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