Nestled in the mountainous hinterlands of the Philippine Cordillera, the Ifugao people of Batad have lived for centuries, eking out a living in upland sweet potato fields and in the extensive rice terraces they carved out of the mountains.

For many years, the Ifugao people led a complex and ritualistic life, appeasing hundreds of deities. Every aspect of their lives was controlled through sacrifice and communication with the spirit world. To prevent violent death, the heads of their enemies were taken through warfare and ambush along trails. The practice of head-hunting was central to...