Jangsuk Kim

AMS Dates from Two Archaeological Sites of Korea: Blind Tests

In interpreting radiocarbon dating results, it is important that archaeologists distinguish uncertainties derived from random errors and those from systematic errors, because the two must be dealt with in different ways. One of the problems that archaeologists face in practice, however, is that when receiving dating results from laboratories, they are rarely able to critically assess whether differences between multiple 14 C dates of materials are caused by random or systematic errors. In this study, blind tests were carried out to check four possible sources of errors in dating results: repeatability of results generated under identical field and laboratory conditions, differences in results generated from the same sample given to the same laboratory submitted at different times, interlaboratory differences of results generated from the same sample, and differences in the results generated between inner and outer rings of wood. Five charred wood samples, collected from the Namgye settlement and Hongreyonbong fortress, South Korea, were divided into 80 subsamples and submitted to five internationally recognized 14 C laboratories on a blind basis twice within a 2-month interval. The results are generally in good statistical accordance and present acceptable errors at an archaeological scale. However, one laboratory showed a statistically significant variance in ages between batches for all samples and sites. Calculation of the Bayesian partial posterior predictive p value and chi-squared tests rejected the null hypothesis that the errors randomly occurred, although the source of the error is not specifically known. Our experiment suggests that it is necessary for users of 14 C dating to establish an organized strategy for dating sites before submitting samples to laboratories in order to avoid possible systematic errors.

Population Fluctuation and the Adoption of Food Production in Prehistoric Korea: Using Radiocarbon Dates as a Proxy for Population Change

Population growth has been evoked both as a causal factor and consequence of the transition to agriculture. The use of radiocarbon ( 14 C) dates as proxies for population allows for reevaluations of population as a variable in the transition to agriculture. In Korea, numerous rescue excavations during recent decades have offered a wealth of 14 C data for this application. A summed probability distribution (SPD) of 14 C dates is investigated to reconstruct population trends preceding and following adoptions of food production in prehistoric Korea. Important cultivars were introduced to Korea in two episodes: millets during the Chulmun Period (ca. 6000–1500 BCE) and rice during the Mumun Period (ca. 1500–300 BCE). The SPD suggests that while millet production had little impact on Chulmun populations, a prominent surge in population appears to have followed the introduction of rice. The case in prehistoric Korea demonstrates that the adoption of food production does not lead inevitably towards sustained population growth. Furthermore, the data suggest that the transition towards intensive agriculture need not occur under conditions of population pressure resulting from population growth. Rather, intensive rice farming in prehistoric Korea began during a period of population stagnation.

Radiocarbon Dating and the Historical Archaeology of Korea: An Alternative Interpretation of Hongryeonbong Fortress II in the Three Kingdoms Period, Central Korea

ABSTRACT Relying heavily upon historical records to build archaeological chronologies, many Korean historical archaeologists question the utility of radiocarbon dating. To challenge this tendency, we test a model based on historical records by analyzing radiocarbon dates. We dated two bulk samples from Hongryeonbong Fortress II, Seoul, South Korea, which is known historically to have been occupied between a.d. 500 and 551. By dividing bulk samples into smaller aliquots, we dated 40 subsamples and statistically estimated consensus dates. The consensus dates do not support expectations of the historical model, as they do not lie within the temporal range provided by historical records. We propose an alternative model that explains both the radiocarbon dates and the historical records. It is suggested that radiocarbon dating can be successfully applied to the reconstruction of historical periods and is a way of mitigating possible biases of models based solely on historical records.

Change in Settlement Distribution and the Emergence of an Early State: A Spatial Analysis of Radiocarbon Dates from Southwestern Korea

Archaeologists have long examined how the emergence of core polities prompts changes in the settlement patterns of peripheral regions through various processes like warfare, patronage claims, control of ritual rites, and unequal balances of trade. According to historical records, there were 54 small Mahan polities in southwestern Korea, and one of these polities, Baekje, grew to become an ancient state by unifying other polities in the 4th century AD. It is assumed that subsequent changes in the settlement patterns of southwestern Korea were caused directly or indirectly by the expansion of Baekje, but the nature of this presumed influence is not fully explained due to difficulties in establishing chronologies and the limited application of spatial analyses. In this paper, radiocarbon ( 14 C) dates, kernel density estimates, and spatial autocorrelation analyses are used to compare Mahan settlement distributions before and after the rise of the Baekje kingdom. The results demonstrate that the spatial distribution of Mahan settlements changed over time, correlating with the emergence of Baekje statehood, but detailed aspects of the settlement patterns observed in each region were not uniform. Baekje applied various expansion strategies and exerted asymmetrical hegemony based on the conditions and responses of peripheral communities.

Bayesian Analysis for Uncertainty of Radiocarbon Dating

Abstract Use of radiocarbon dating is increasing for chronology; however, its variability and discrepancy with existingchronologies can cause doubts in regards to credibility. In this paper, we explore factors that inuenceradiocarbon dating variabilities. We obtained estimated radiocarbon ages by sending identical samplesto several labs multiple times. A Bayesian method was used to analyze the obtained data. From theanalysis, we conclude that some factors (such as type of labs and megasamples) can induce variabilitywhen estimating radiocarbon age. We identify the size of variability caused by each factor and analyze theestimated variability in each lab corresponds with the reported variability.Keywords: radiocarbon dating, archaeological chronology, Bayesian statistics, consensus value, variability 1. 서론 미국의리비(Willard F. Libby)에 의해 1940년대에 개발된방사성탄소연대측정법은고고학 연대측정의한 방법으로 널리 쓰이고 있다. 한국고고학에서는 1990년대 후반부터 이용이급증하여 현재는 9000건이넘는 연대측정결과가 보고되어 있다. 하지만, 한국고고학에서는 방사성탄소연대측정치가 연대판정에 적극적으로 이용되지 못할 뿐 아니라 방사성탄소연대 회의론 또는 무용론까지도 제기되고 있다. 그이유는, 첫째, 동일한 시점을나타낼 것으로 기대되는 시료의측정결과들이고고학적 동시기로 보기 어려울 만큼 서로 간에 큰 차이를 보이기도 하고, 둘째, 탄소연대측정결과가 고고학적으로 이미 수립된기존의편년과 현저한 차이를 보이는 경우가 흔히 발생하기 때문이다. 탄소연대측정결과에 대한 부정적경향은편년에 문헌사료를 적극적으로 이용하는 삼국시대의고고학에서가장두드러지는데, 이는, 위의두문제가 설사 해결된다고 하더라도 탄소연대측정은그 결과가 원천적으로 가질 수밖에 없는 수십년또는 1세기의오차로 인해 역사적 사건과 고고학 자료의세밀한 시간적 배열에 적절한 답을제공하지못할 것이라는 인식에 상당부분 기인한다. 이로 인해, 방사성탄소연대측정결과를 어떻게 수용하여야 할것인지는 한국고고학계에서논란에 휩싸여 있다 (Kim, 2014).