One of the oldest human ideas is that we are somehow different from animals, somehow superior to them. That’s a mistake, argues the environmental philosopher Melanie Challenger. “Many of the things we most value — our relationships, the romantic sensations of attraction and love, pregnancy and childbirth, the pleasures of springtime, of eating a meal — are physical, largely unconscious and demonstrably animal,” she writes in her book “How to Be Animal: A New History of What It Means to Be Human.” The consequences of resisting our fellowship with other species, she argues, have been devastating to them and to the planet. Challenger’s arguments are fascinating in their own right, but they also have a particular resonance at this moment of tremendous technological advancement. Humans have long defined ourselves by our cognitive intelligence, yet the machines we’re building are rapidly surpassing our minds. What does it mean to be human in a world where we are no longer superior by the standards we’ve created? Have we set ourselves up for a specieswide existential crisis? And how can embracing our status as animals help us navigate this bizarre future?