Saraswat Brahmins are Brahmins who lived on the banks of the former Saraswati River that once flowed in northern India. Saraswats are considered among the oldest and most widespread community in India, still preserving their own culture. Around 1900 BC, the river Saraswati started vanishing under ground and the people on its banks started migrating to other parts of India thus forming sub-communities.

http://en.wikipedia.org/wiki/Saraswat_Brahmin