Generating Anthropological and Archeological Hypotheses in Okinawa through Agent-Based Simulation
It is thought that agriculture was introduced to the Okinawa Islands from the ninth to the tenth century , before the start of the Gusuku period in the eleventh century ( Takamiya , 2002 ).
This hypothesis is supported by the discovery of grains excavated from ninth century ruins . The sudden onset of agriculture is assumed to be because of the immigration of agricultural peoples .
There were large differences before and after the start of the Gusuku period . First , there was a population explosion : there are seven times more ruins in the Gusuku period than in the Shell midden period , an antecedent of the Gusuku period ( Takamiya , 2005 ). It is thought that the population increased during the Gusuku period because of the start of agriculture . Second , there were large differences in anthropological morphology . The bones of the people before the Gusuku period indicate that they had low and small faces ( Asato & Doi , 2011 ; Doi , 1998 ; Doi , Hirata , Zukeran , & Sensui , 1997 ), while the bones of the people in the Gusuku period show that they were heavyset and tall , with dolichocephaly ( long narrow head ). It is assumed that this change also follows the population replacement by the immigrants bringing agriculture from the Japanese mainland . Third , in evidence of immigrants bringing agriculture from the Japanese mainland , there is a study of ancient mitochondrial DNA ( mtDNA ) from the people of the Gusuku period ( Shinoda , Kakuda , & Doi , 2013 ). The mtDNA haplogroup D4 , which has high frequency on the Japanese mainland , also has high frequency in the people of the Gusuku period . Fourth , there were large differences in the style of pottery . In the Gusuku period , while the pottery of the distribution products — which is influenced by the pottery style of the Japanese mainland — was widely propagated , the style of pottery made in the settlement varied from the conventional native style to a different style , which is an imitation of the distribution products ( Miyagi , 2011 ).
However , the process of these changes following the introduction of agriculture is unknown . Therefore , we apply ABSs to the hypothetical processes of the anthropological and archeological change following the introduction of agriculture . Similar to our previous study ( Sakahira & Terano , 2014b ), the ABSs in this paper deal with the diffusion process of the trait gene , mtDNA , and the vertical transmission of pottery styles under agricultural diffusion . In this study , we also add the horizontal transmission of pottery styles to the previous simulation model .
2 . Description of the Simulation Model based on ODD Protocol
Our simulation model follows the Overview , Design concepts , and Details
( ODD ) protocol ( Grimm et al ., 2006 ; Grimm et al ., 2010 ). This protocol is intended to address the criticism that agent-based models lack reproducibility . Furthermore , it aims to improve the integrity and standardization of the model description .
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