AT THE END of 2019, David Finnigan, a writer and performer from Canberra, agreed to do his father a favour. John Finnigan, a climate scientist, was being treated in hospital for a spinal infection, and the drugs made him too foggy to work on his paper about “six key moments in human history, six turning points where we changed course”. The premise was that humanity is “an adolescent species”, still growing up, but by examining these turning points in our collective past we might be able to glean lessons, or morals, to help us secure our admittedly precarious future. How, for instance, had Homo sapiens survived the catastrophic eruption of Toba, a supervolcano in Sumatra, which nearly wiped out all life on earth some 74,000 years ago? What might the…