them consistent with other ancient Peruvians. She found, for example, a universal occurrence of shovel-shaped upper incisors and a near-complete absence of the cusp of Carabelli on upper molars — characteristics consistent with other indigneous peoples and inconsistent with Europeans. According to the analysis of the Chachapoyas objects made by the Antisuyo expeditions of the Instituto de Arqueología Amazónica, the Chachapoyas do not exhibit Amazon cultural tradition but one more closely resembling an Andean one. Given that the terrain facilitates peripatric speciation, as evidenced by the high biodiversity of the Andean region, the physical attributes of the Chachapoyas are most likely reflecting founder effects, assortative mating, and/or related phenomena in an initially small population sharing a relatively recent common ancestor with other indigenous groups. The anthropomorphous sarcophagi resemble imitations of funeral bundles provided with wooden masks typical of the "Middle Horizon", a dominant culture on the coast and highlands, also known as the Tiwanaku–Wari culture. The "mausoleums" may be modified forms of the chullpa or pucullo, elements of funeral architecture observed throughout the Andes, especially in the Tiwanaku and Wari cultures. Population expansion into the Amazonian Andes seems to have been driven by the desire to expand agrarian land, as evidenced by extensive terracing throughout the region. The agricultural environments of both the Andes and the coastal region, characterized by its extensive desert areas and limited soil suitable for farming, became insufficient for sustaining a population like the ancestral Peruvians, which had grown for 3000 years. This theory has been described as "mountainization of the rain forest" for both geographical and cultural reasons: first, after the fall of the tropical forests, the scenery of the Amazonian Andes changed to resemble the barren mountains of the Andes; second, the people who settled there brought their Andean culture with them. This phenomenon, which still occurs today, was repeated in the southern Amazonian Andes during the Inca Empire, which projected into the mountainous zone of Vilcabamba, raising examples of Inca architecture such as Machu Picchu. Characteristics The architectural model of the Chachapoyas is characterized by circular stone constructions as well as raised platforms constructed on slopes. Their walls were sometimes decorated with symbolic figures. Some structures such as the monumental fortress of Kuelap and the ruins of Cerro Olán are prime examples of this architectural style. Chachapoyan constructions may date to the 9th or 10th century; this architectural tradition still thrived at the