culture of Goguryeo and Baekje where Chinese influence was more pronounced. Other states Other smaller states or regions existed in Korea before and during this period: Gaya confederacy, Gaya was a confederacy of small kingdoms in the Nakdong River valley of southern Korea since AD 42, growing out of the Byeonhan confederacy of the Samhan period. Gaya polities had economies that were based on agriculture, fishing, casting, and long-distance trade. Constantly engaged in war with the three kingdoms surrounding it, Gaya was not developed to form a unified state, and was ultimately absorbed into Silla in 562. Dongye, Okjeo, and Buyeo, all three conquered by Goguryeo Usan (Ulleung-do) tributary of Silla Tamna (Jeju-do) tributary of Baekje Religion Centuries after Buddhism originated in India, the Mahayana Buddhism arrived in China through the Silk Route in 1st century AD from Tibet, then to Korean peninsula in 3rd century during the Three Kingdoms Period from where it transmitted to Japan. In Korea, it was adopted by the state religion by 3 constituent polities of the Three Kingdoms Period, first by the Goguryeo ruling tribe of Geumgwan Gaya in 372 AD, by the Silla in 528 AD, and by the Baekje in 552 AD. Decline Allied with China under the Tang dynasty, Silla conquered Goguryeo in 668, after having already conquered Gaya in 562 and Baekje in 660, thus ushering in the North–South states period with Later Silla to the south and Balhae to the north, when Dae Jo-young, a former Goguryeo military officer, revolted against Tang Chinese rule and began reconquering former Goguryeo territories. Archaeological evidence Archaeologists use theoretical guidelines derived from anthropology, ethnology, analogy, and ethnohistory to the concept of what defines a state-level society. This is different from the concept of state (guk or Sino ko: 國, walled-town state, etc.) in the discipline of Korean History. In anthropological archaeology the presence of urban centres (especially capitals), monumental architecture, craft specialization and standardization of production, ostentatious burials, writing or recording systems, bureaucracy, demonstrated political control of geographical areas that are usually larger in area than a single river valley, etc. make up some of these correlates that define states. Among the archaeology sites dating to the Three Kingdoms of Korea, hundreds of cemeteries with thousands of burials have been excavated. The vast majority of archaeological evidence of the Three Kingdoms Period of Korea consists of burials, but since the 1990s there has