The development of rhythm is said to have its roots in natural selection. Early hominids in the African savanna used rhythmic techniques to establish their "battle trances," giving them a leg up on their natural predators. And, of course, rhythm has always played a role in human courtship. But beyond the ability to survive and mate, rhythm provides the backbeat of musical traditions all over the globe, several of which will be on display at the World Percussion Arts Festival. Many of the works presented this year are from Asian drumming traditions, and place an emphasis on storytelling. "Rouge," performed by Maikaze Daiko, explores the horrific rule of the Khmer Rouge regime in 1970s Cambodia. Grandmaster Seiichi Tanaka of the S.F. Taiko Dojo makes a special appearance on Saturday, and the Ong Dance Co. brings a contemporary, modern update to traditional Korean dance and percussion arts. Other featured guests include GONNA, on its first U.S. tour, and the West African/Punjabi dance troupe Duniya Dance and Drum Co.