The Ubaid Period a prehistoric period of Mesopotamia. (ca. 6500 to 3800 BC) The archaeological record shows that Arabian Bifacial/Ubaid period came to an abrupt end in eastern Arabia and the Oman peninsula at 3800 BC. After that there is no evidence of human presence in the area for approximately 1000 years, the so-called "Dark Millennium" The Ubaid culture was characterized by large village settlements, with multi roomed rectangular mud-brick houses, and the first temples of public architecture in Mesopotamia and a two tier settlement hierarchy of centralized large sites surrounded by smaller village sites. Domestic equipment included a distinctive fine quality buff or greenish colored pottery decorated with geometric designs in brown or black paint. The appearance of the Ubaid has sometimes been linked to the so-called Sumerian problem, related to the origins of Sumerian civilization. The Vinca culture, also known as Turda? culture or Turda?-Vinca culture, is a Neolithic archaeological culture in Southeastern Europe, dated to the period 5500–4500 BCE. It has startling similarities to the Ubaid culture. Vinca artifacts were made with considerable levels of technical skill. A two-stage method was used to produce pottery with a polished, multi-coloured finish, known as 'Black-topped' and 'Rainbow Ware'. Sometimes powdered cinnabar and limonite were applied to the fired clay for decoration. The Vinca site of Plocnik has produced the earliest example of copper tools in the world. Both cultures depicted their peoples as having reptilian or alien grey-like features. Could this be evidence of an ancient reptilian alien race on Earth?