There doesn't exist anywhere near enough nuclear weapons to kill all humans. Even in the 1980s, people were predicting between 20 and 100 million immediate Amer

There doesn't exist anywhere near enough nuclear weapons to kill all humans. Even in the 1980s, people were predicting between 20 and 100 million immediate American deaths from a full-scale Soviet attack, and since then there are much fewer nuclear weapons. See e.g. the discussion in this comment thread: https://slatestarcodex.com/2015/10/31/ot32-when-hell-is-full-the-thread-will-walk-the-earth/#comment-255524 https://slatestarcodex.com/2015/10/31/ot32-when-hell-is-full... It has been suggested that humans recovered from a population bottleneck of less than 30,000 individuals (the Toba catastrophy). A nuclear war would leave billions alive.