If we take 'happiness' to be the fitness function of human evolution and a driver for adaption then I think it highly unlikey humans would ever change to become less happy. Infact, I might suggest that human happiness (amount of) is likely to be the one thing in common to modern civilizations as to those 200,000 years ago.

In addition, be careful to use the word 'evolution' with timeframes as miniscule as 200,000 years - the author correctly uses the word 'adoption'.