Field terraces are notoriously difficult to date – but historically of high significance. Here the author uses a Bayesian model applied to radiocarbon dates to date the tiered rice fields of the northern Philippines. They turn out to have been built in the sixteenth century probably by peoples retreating inland and upland from the Spanish.

The dispersal of rice (Oryza sativa) following domestication influenced massive social and cultural changes across South, East, and Southeast Asia. The history of dispersal across islands of Southeast Asia, and the role of Taiwan and the Austronesian expansion in this process remain largely unresolved. Here, we reconstructed the routes of dispersal of O. sativa ssp. japonica rice through Taiwan and the northern Philippines using whole-genome re-sequencing of indigenous rice landraces coupled with archaeological and paleoclimate data. Our results indicate that japonica rice found in the northern Philippines diverged from Indonesian landraces as early as 3500 BP. In contrast, rice cultivated by the indigenous peoples of the Taiwanese mountains has complex origins. It comprises two distinct populations, each best explained as a result of admixture between temperate japonica that presumably came from northeast Asia, and tropical japonica from the northern Philippines and mainland Southeast Asia respectively. We find that the temperate japonica component of these indigenous Taiwan populations diverged from northeast Asia subpopulations at about 2600 BP, while gene flow from the northern Philippines occurred before ∼1300 years BP. This coincides with a period of intensified trade established across the South China Sea. Finally, we find evidence for positive selection acting on distinct genomic regions in different rice subpopulations, indicating local adaptation associated with the spread of japonica rice.

The idea that complex agricultural and irrigation systems lead to centralized control has been refuted in the last three decades. Indeed, ethnographic and archaeological literatures regarding this relationship have been forthcoming in recent years. This article contributes to this body of work by investigating the Ifugao agricultural system. Spatial patterning and ethnographic information from Ifugao suggest that a recursive relationship between the landscape and its users exist where environmental constraints necessitate cooperation among terraced rice field systems. Correlated to this discussion, this article examines the applicability of the “house” concept in defining Ifugao social organization. Results of my ethnographic investigations suggest that the house concept complements kinship analysis, and thus, contributes to a better understanding of Ifugao social relationships. Moreover, this article argues that the agricultural field becomes the node of Ifugao social relationships. In this sense, the agricultural field becomes an emergent property that defines Ifugao social organization. This study provides archaeologists with a model to investigate the precolonial social structure of the Ifugao.

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