 Rohl believes the catalyst for this sudden development was the influx of a Mesopotamian "foreign elite" who made their way to Egypt by sailing around the coastline of the Arabian Peninsula into the Red Sea ultimately dragging their boats across the desert to the Nile.Rohl notes numerous pre-dynastic rock carvings found in several locations from Wadi Abbad to Abydos which is suggested depict large Mesopotamian style boats with crews of up to 75, some of which appear being pulled across land.Rohl believes the most dramatic evidence to support this theory is the sudden introduction of distinctly Mesopotamian "niched-facade", also known as "palace facade", architecture found in several early Dynastic sites, most notably the large 1st Dynasty mastabas at Saqqara.