In the early 20th century, Egyptologist Sir William Matthew Flinders Petrie deduced that skeletal remains found at pre-dynastic sites at Naqada (Upper Egypt) indicated the presence of two different races, with the Dynastic Race, also referred to as the "Followers of Horus", differentiated physically by a noticeably larger skeletal structure and cranial capacity. Petrie concluded that the physical differences of the remains in conjunction with the previously unknown burial styles, uncharacteristic tomb architecture, and abundance of foreign artifacts, implied this race must have been an invading ruling elite that was responsible for the seemingly sudden rise of Egyptian civilization. Based on plentiful cultural evidence, Petrie determined that the invader race had come from Mesopotamia, and imposed themselves on the native Badarian culture to become their rulers. Petrie adduced new architectural styles—the distinctly Mesopotamian "niched-facade" architecture—pottery styles, cylinder seals and a few artworks, as well as numerous Predynastic rock and tomb paintings depicting Mesopotamian style boats, symbols, and figures.