Why are you so pessimistic about humans?
I am not pessimistic about humans. I am, rather. realistic about the nature of the human. For me humans aren't evil, good or bad. they just are. I try not to confuse 'ought' and 'is.' I do not believe in genetic determinism but I do believe that we carry much evolutionary baggage. There are probably no Caliban's whom Prospero, in "The Tempest," described as: "A devil, a devil born, on whose nature/ Nurture can never stick;........." as there are likely no saints. Humans that passed on their genes were greedy, gluttonous, hypocrites who rarely worried about means to their ends. They were highly suspicious creatures, bereft of altruism, driven by self interest. They rarely, if ever, thought deeply, as most circumstances involved surviving immediate dangers like starvation or being chased by predators, best dealt with by instinct.
To the extent that evolution is such a slow process our brains are still running on those very same survival principles. Fortunately they are tempered by cultural, political, economic and social innovations such as laws, tribal affiliations, security and humanism.
It is instructive to consider that the area around Chernobyl [http://news.nationalgeographic.com/2016/04/060418-chernobyl-wildlife-thirty-year-anniversary-science/] is today thriving with the local flora and fauna, well beyond anything seen during the time before humans disappeared from the area.
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