Climate change.
Think about how many times you control your local micro climate around you. Think about how many times you talk about the weather with whomever.
It's a big force in the human condition.
About as many as the moments in which we have to talk with somebody but lack something better to break the ice!
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P.S.: I've read so far about a number of possible cases for which humans started to walk upright and none had climate change as a primary cause.
Climate change.
Think about how many times you control your local micro climate around you. Think about how many times you talk about the weather with whomever.
It's a big force in the human condition.