These HG probably got rather deadly diseases from the animals they hunted& ate but these were self-limiting due to the relative isolation. Moreover those specializing in certain prey, like bats or primates most like underwent natural selection against the pathogens acquired from those sources (i.e. natural immunity) –like say bat- & primate- eating tribes from different parts of India – circulating antibodies against bat-borne viruses for e.g.
This probably went hand-in-hand with the practice of active xenophobia that was strongly selected for as a defense against infection-laden foods & pathogens acquired from strangers who had immunity to them.(5)
With the neolithic a new pathogen-community developed from the domesticates & this continued over a long period. It had a 2-edged effect:
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- probably increased the ambient disease load among the neolithic agriculturalists s – this is supported by the fact that many of our modern pathogens can be traced back to domesticates
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- On the +side it probably gave the neolithics an edge in their encounters with HG & helped the former in wiping them out/absorbing them.
Rural preference
I suspect this was 1 of the reasons that after the Indo-Aryan conquest of northern India there considerable hesitancy in returning to the peak urbanity for it was associated with a large disease load that the Arya elite avoided with their more rural lifestyle. In fact they even seem to have even advocated the araNya for part of their life suggesting that they retained some of their old ways at least among the elite.
In light of this 1 wonders if the so-called second urbanization of india was accompanied by a Harappan genetic rebound that provided the disease resistance they had acquired in their original urban phase to sustain the new urbanization. The old H urban organizational principles & jati segregation, which moderns thunderously object to, might ’ve also arisen as behaviors to limit urban pathogen spread.