All of us animals, humans and non, lost a great friend and advocate with the death of primatologist, author, and storyteller Frans de Waal in March.

Gently and convincingly, de Waal debunked the arrogant assumptions that only humans experience complex emotions, are capable of empathy, or engage in complex thoughts and behaviors.

A prolific writer, de Waal authored the bestselling “Are We Smart Enough to Know How Smart Animals Are?” and “Mama’s Last Hug: Animal Emotions and What They Tell Us About Ourselves.” His style is approachable, and the stories he shares are profound. One of my favorites is the study he did on pay equity with Capuchin monkeys. Spoiler: Monkeys recognize — and push back on — unfairness, as do dogs, chimps, and many other non-humans.

Unafraid of controversy, de Waal took on more than moral behavior in animals, addressing “alpha” male behavior, gender differences, and much more, consistently challenging “accepted” wisdom and expanding our understanding of non-humans’ abilities.

His final work, on how humans’ thinking about animals has evolved, will be released next year, according to the New York Times obituary for de Waal.