[Balazs]

I've just read a great essay about the Sumerian - Scythian relationship. It quotes ancient writers who claimed that the Scythians were originally from the area of Persia, lived in stone houses and had agriculture. Also that they were the first nation having a civilization with laws.
An other source claimed that Scythians and Egyptians had a dispute about the age of their own culture.
Ancient Indo-Europeans did not respect their deaths (at least not in a way the nomad people did) - see the Roman and Greek cremation or the Indo-Iranians way who put the dead body out for the vultures and other animals. Meanwhile nomad people such as Hungarians and yes, the Scythians too in fact did bury the bodies.

These things would clearly abolish the Indo-Iranian origin of the Scythian people (which is based on no evidence) and would assume that the Sumerians after the fall of their civilization fled to the North changing into a nomadic way of life.