Asia's various modern cultural and religious spheres correspond roughly with the principal centres of civilisation. West Asia and Central Asia have their cultural roots in the pioneering civilisations of the Fertile Crescent and Mesopotamia.South Asia, India and the Indosphere emanate from the Indus Valley Civilization. The East Asian cultural sphere developed from the Yellow River civilization. Southeast Asia's migration waves of more varied ethnic groups are relatively recent. Commercial interaction with South Asia eventually lead to the adoption of essential cultural elements from India and to a lesser extent from China.[8][9] North Asia's harsh climate and unfavorable soil proved to be unsuited to permanently support large urban settlements and only permits the presence of a pastoral and nomadic population, spread over large areas. Nonetheless, North Asian religious and spiritual traditions eventually diffused into more comprehensive systems such as Tibetan Buddhism that developed its own unique characteristics (e.g. Mongolian Buddhism).