The First Dynasty of ancient Egypt (Dynasty I) covers the first series of Egyptian kings to rule over a unified Egypt. It immediately follows the unification of Upper and Lower Egypt, possibly by Narmer, and marks the beginning of the Early Dynastic Period, a time at which power was centered at Thinis. The date of this period is subject to scholarly debate about the Egyptian chronology. It falls within the early Bronze Age and is variously estimated to have begun anywhere between the 34th and the 30th centuriesBC. In a 2013 study based on radiocarbon dates, the beginning of the First Dynasty—the accession of Narmer (commonly known as Menes)—was placed at 3100BC give or take a century (3218–3035, with 95% confidence). The dynasty Information about this dynasty is derived from a few monuments and other objects bearing royal names, the most important being the Narmer Palette and Narmer Macehead, as well as Den and Qa'a king lists. No detailed records of the first two dynasties have survived, except for the terse lists on the Palermo Stone. The account in Manetho's Aegyptiaca contradicts both the archeological evidence and the other historical records: Manetho names nine rulers of the First Dynasty, only one of whose names matches the other sources, and offers information for only four of them. Egyptian hieroglyphs were fully developed by then, and their shapes would be used with little change for more than three thousand years. Large tombs of pharaohs at Abydos and Naqada, in addition to cemeteries at Saqqara and Helwan near Memphis, reveal structures built largely of wood and mud bricks, with some small use of stone for walls and floors. Stone was used in quantity for the manufacture of ornaments, vessels, and occasionally, for statues. Tamarix ("tamarisk" or "salt cedar") was used to build boats such as the Abydos boats. One of the most important indigenous woodworking techniques was the fixed mortise and tenon joint. A fixed tenon was made by shaping the end of one timber to fit into a mortise (hole) that is cut into a second timber. A variation of this joint using a free tenon eventually became one of the most important features in Mediterranean and Egyptian shipbuilding. It creates a union between two planks or other components by inserting a separate tenon into a cavity (mortise) of the corresponding size cut into each component." Biological anthropologist, S.O.Y. Keita, conducted a