I was reflecting a bit on the history of philosophy and religion and how they view human life. My question is the following: Why does it seem ( at least from my readings and knowledge, I might have confirmation bias ) that pessimism is more of prevelant view in philosophy/religion?
Eastern religions basically see everyday life as samsara (perpetual cycle of infinite suffering), something to escape and be liberated of, offering moskha or nirvana as path, which heavily relies on asceticism, denial of wordly pleasures and a need to transcend human condition in general (nirvana is literally seen as "extinguishment" of desire, will to live/become). Christianity views humans "tainted" with original sin, and it's main objective it's salvation trough union with God/Christ (this need for transcendental value its present here again, altough in very different way compared to eastern religions). The main branch of philosophy that deals with human existence, existentialism, seems again heavily influenced by this negative sentiment, all the main thinkers seem to at least partake in this view: Kierkegaard, Dostoievski, Nietzsche, etc.
We know from a biological perspective that the objective ("meaning" in some way) of life is further propagation, therefore existence is tuned towards survival and not happiness ( or more loosely positive emotion, since happiness is such an abstract concept).
It seems to me that philosophical optimism doesn't have as much as relevance or attention in opposition to philosophical pessimism. Do you think this is true or not, and why do you think it? I'd appreciate philosophical conjectures or "scientific ones" (like maybe positive emotion is less intense and frequent as negative emotion).