" Humans diverged from apes about as long ago as African and Asian elephants did from each other, and they are genetically as close or distant. Yet we freely call both of those species “elephants” while obsessing over the specific point at which our own lineage moved from being an ape to being human. We even have special words for this process, such as humanization and anthropogenesis. That there was ever a point in time is a widespread illusion, like trying to find the precise wavelength in the light spectrum at which orange turns red. Our desire for sharp divisions is at odds with evolution’s habit of making extremely smooth transitions. "

― Frans de Waal , Mama's Last Hug: Animal Emotions and What They Tell Us about Ourselves