If we accept the biological approach to happiness, then history turns out to be of minor importance, since most historical events have had no impact on our biochemistry. History can change the external stimuli that cause serotonin to be secreted, yet it does not change the resulting serotonin levels, and hence it cannot make people happier.
Sounds like Harari needs to read up on epigenetics. There *can* be generational change in biochemistry as a result of historical events. Look to survivors of slavery, wars, and other historical hardships and see the effects of those events on their children who did not personally endure the events themselves.
