my first theory is, i think that pashtuns are a mixture of central asian Caucasians, mongoloids and the indians groped together in one region who's natural restrictions and landscape made them the naturalised citizens of that territory
pashtun people also vary region to region
in pakistani side, there are pathuns who live in hindu kush mountains(like swatis, chitralis etc), and then there are pashtuns who dwell in sulaiman mountains(like mehsuds, waziristanis etc), both differ in topography
when i say indian then the proof is pashtuns practiced budhism which the north indians also practiced, i don't see any resemblence of judaism monothiestic influence in budhism, both are far apart, i don't see how pashtuns lived a separate life style surely they were influenced by the regions surrounding them like iran, south asia, central asia
my second theory is, pashtuns may well be the outer reach of iranian group who got isolated in the hindukush region and later mixed up with local indian, turk, or the russian(central asian Caucasian) culture
i maybe wrong though