"Von Soden observes that “since the discovery of the Indus civilization … it has been almost universally accepted that the Sumerians immigrated from the east.” The immigrants are regarded as having arrived in lower Mesopotamia either at the beginning of the Ubaid period (c. 5000 B.C.) or at the beginning of the Uruk period (perhaps c. 3500 B.C., but perhaps as late as 3250). In either case, the Sumerians seem to have fitted easily into an advanced Chalcolithic culture where writing was already in the early stages of development. Therefore, the implication is that they must have been from another advanced culture, and that points to the East. Bottero agrees that “the Sumerians must have arrived in Mesopotamia during the fourth millennium, apparently from the southeast.” Von Soden further observes that “this immigration could have succeeded entirely by land if the Sumerians immigrated from somewhere in northern India,” and refers suggestively to “the westward migration of the Sumerian groups, whose language may have been related to the Dravidian languages of India.”"