Sumer
Sumer () is the earliest known civilization in the historical region of southern Mesopotamia, modern-day southern Iraq, during the Chalcolithic and Early Bronze ages, and one of the first civilizations in the world along with Ancient Egypt and the Indus Valley. Living along the valleys of the Tigris and Euphrates, Sumerian farmers were able to grow an abundance of grain and other crops, the surplus of which enabled them to settle in one place. Prehistoric proto-writing dates back before 3000 BC. The earliest texts, from c. 3300 BC, come from the cities of Uruk and Jemdet Nasr; early cuneiform script emerged around 3000 BC.
Mu (lost continent)
There is evidence that the civilizations of the Americas and the Old World developed independently of each other and, in fact, agriculture and urban societies probably first developed after the end of the Ice Age, somewhere in the Levant some 10,000 years ago and gradually spread outwards from there to the rest of the Old World. The development of the oldest known cities, such as Çatalhöyük, can more easily be attributed to local and gradual evolution than to the coming of refugees from a "superior civilization".