In his swan song, Frans de Waal writes about the feelings of chimpanzees, bonobos, and other animals – and about the biologists who did not want to take such emotions seriously.

In his posthumous book, Frans de Waal reflects on the emotional lives of animals, challenging the long-held view of them as mere instinct-driven machines. He recounts his academic journey advocating for a more empathetic understanding of animal behavior, highlighting the shift in scientific perspectives during his lifetime. De Waal emphasizes the recognition of moral feelings like empathy and compassion in various species, asserting that social animals genuinely care for one another. He critiques the overemphasis on human brain size, questioning its significance in cognitive abilities. The book serves as a memoir, a history of scientific thought, and a tribute to pioneering figures in primatology, illustrating the complexity of animal minds and the importance of observing their behaviors without anthropocentric biases.