I'm trying to create a world where after really violent wars, Humanity nearly disappeared due to the power of newly developped technologies. After that, survivors decide through multiple modifications (DNA or someting like that...) to connect all people born after them with a sort of collective consciousness, but for feelings, to try to create a "global empathy" to nullify violence.
I'm searching for reason why this solution worked on a short period, the test period but went wrong after a long time (possibly on next generations), leading to a worse world than ever.