Talk of people of same group of languages not different.Europeans like the Iberians, Gauls, Britons, Italian groups, etc, etc. who were closer to each other are very much different from each other.
you are quite poor in linguistics italians are of italic languages, britons and gauls of celtic and iberians of another different group.
do you consider 8th century spanish and portuguese as different?
BTW, I am talking of gangetic plains not punjab which was culturally not as advanced as rest of north india.