well thats almost impossible to do since Scythians were around northwest India possibly a thousand years before Christ...all you can really go on is physical evidence, such as landmarks, clan names, eye colour variations, height, build, hair colour, facial characteristics etc. Again, this is a theory, but this is the only one that actually has proof.
There are also many scholars/historians/professors that have said that Jatts can be classified as a race. Professor Mcleod (University of Cambridge), H.S. Duleh, Dr. Babar Singh Dhillon, Rose etc.
Again, dont forget "randomly-selected".
The Scythians were also known as the most feircest warriors, avid hunters, avid horsemen and had conquered many lands when coming towards northwest India and Pakistan....so where did these people vanish? Such a strong race of kings/soldiers, that had stemmed all the way from Eastern Europe...and they just vanish all of a sudden? Doesnt add up.