In his book "Sapiens - a Brief History of Humankind", Harari argues that the biochemistry of "happiness" in any person can only move within bounds, dictated by genetics.

He also argues that happiness only improves momentarily when objective circumstances improve, and only e.g. a degenerative disease or permanent physical pain can result in lasting change. This seems to be widely accepted and is backed by numerous studies.

I could not, however, find any studies supporting his statement that events such as the agricultural revolution had no lasting impact on humankind's objective happiness.

Are there any scientific studies on the biochemistry of happiness of generations that lived before and after major historic events like the cure of a disease that affected large parts of the studied community?

Whats psychology's take on human happiness throughout history?

Please suggest edits, as I am no expert on any of this.