Abiathar, I believe that mankind, at least our species Homo Sapiens, had a propensity for spirituality. paleo-anthropologists interpret prehistoric cave paintings as having a religious/ritualistic component - we worshipped what we ate. This however has nothing to do with an anthropomorphic 'god' that you mentioned. You could have spirituality and other beliefs such as animism and ancestor worship without a personal god.
"What is temporary can give only temporary happiness!"
We can be happy throughout our entire lifespan of three score and ten years. That would be temporary but fulfilling. No god needs to be involved.
"That means humans—whether in poverty or in material abundance—would seek spirituality, our inherent nature."
And you assume that it has to be a theistic spirituality that is tied in to belief in god/s. As far as poverty and riches are concerned it is well known by sociologists that poverty stricken areas tend to be more religious - religions that emphasize an afterlife of rewards. Two examples are, the deep south, (the 'Bible Belt') in the United States and ghetto areas. While well off people may be religious/spiritual impoverished people need some extra incentive in their miserable lives. Poverty breeds more religiosity than wealth.
And somewhat off topic:
"Just like water has TEMPORARY nature [becoming vapor when heated above 100 degree] and PERMANENT nature [liquidity],"
Water in all three forms can have a PERMANENT nature. Examples:
- An ice planet, too far from its sun for its ice to melt.
- A planet, too warm to freeze and without an ocean, with water vapor making up its entire atmosphere .
- A water world where there is no freezing.