NTHE Questions #5 and #6

What would Planet Earth have been like if Homo sapiens female had been genetically similar to female praying mantises or female black widow spiders (i.e., practicing sexual cannibalism)?

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Assume you are politically omnipotent and can convince everyone on Earth that human extinction is assured in decades … what activities or projects, if any, would you persuade humanity to engage in, or disengage from? Why would it be worthwhile? Would it transcend or depreciate futility?