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In 1978, at 21 and fresh out of Harvard, Robert Sapolsky went to Kenya to watch a troop of wild baboons, and he went back nearly every year for about 25 years, measuring the animals’ stress hormones. Back at Stanford, where he is a professor of biology, neurology and neurosurgery, he studied what those same hormones do to neurons in the brain. His books carry that double life to general readers: why chronic stress makes humans ill when it rarely does zebras, what happened to his baboons, and, in Behave and Determined, what biology says about violence, kindness and free will. This guide covers his seven key books, in order, and where to begin.
By Lisanne Swart · 7 key books · 1992–2023 · Updated October 2026
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Quick answer
Robert Sapolsky has written seven books. The best known are Behave (2017), winner of the Los Angeles Times Book Prize for science and technology, Why Zebras Don’t Get Ulcers (1994), A Primate’s Memoir (2001) and Determined (2023), his argument that free will does not exist. Start with Why Zebras Don’t Get Ulcers, the book built on his own research into stress.
Where to Start with Robert Sapolsky
If you want the book his research is built on
→ Why Zebras Don’t Get Ulcers (1994) — stress, hormones and why it makes us ill.
If you want a memoir rather than a science book
→ A Primate’s Memoir (2001) — his years with the baboons in Kenya.
If you want his big synthesis
→ Behave (2017) — the biology behind human violence and kindness.
If you want the argument everyone debates
→ Determined (2023) — the case against free will.
7 Robert Sapolsky Books, in Order
Stress, the Aging Brain, and the Mechanisms of Neuron Death
His academic monograph, published by MIT Press. It reviews the animal research on glucocorticoids, the adrenal stress hormones such as cortisol, and argues that prolonged exposure to them can leave neurons in the hippocampus more vulnerable to strokes, seizures and possibly Alzheimer’s disease. It is written for scientists, not general readers.
Why Zebras Don’t Get Ulcers
A zebra’s stress is a short crisis, such as outrunning a lion; human stress is often chronic, such as worrying about a job. Sapolsky explains how the same hormones that save an animal in an emergency damage the body when they stay switched on, and how social factors such as poverty and child abuse raise the risk of disease. The last chapter is about coping. He revised it in 1998 and again in 2004.
The Trouble with Testosterone
A collection of essays. The title essay looks at how far the hormone really explains male aggression; others ask whether wild primates treat themselves with medicinal plants, follow a baboon troop that discovers a tourist lodge’s garbage dump, and look for the neurobiological roots of religious belief. In Britain it was published as Junk Food Monkeys.
A Primate’s Memoir
His account of the years with one baboon troop in Kenya, from his first season at 21 onwards, alternating the troop’s rivalries with his own life in East Africa: Masai neighbours, his camp manager Samwelly, and a trip into Uganda during the Uganda–Tanzania War. His last visit in the book is a far darker one for the troop. It was nominated for the Aventis Prize for Science Books in 2002.
Monkeyluv
Eighteen essays on how genes and environment shape behaviour together: how hormones, nutrients and the immune system affect thinking, why openness to new music and new experiences tends to close at a certain age, and the parent who fabricates a child’s illness in Munchausen’s syndrome by proxy.
Behave
An 800-page attempt to explain a single act, violent or kind, by working backwards in time: what happened in the brain a second before, the hormones of the hours and days before, then adolescence, childhood, the womb, genes, culture and evolution. Along the way it covers tribalism, hierarchy, morality, and war and peace. It won the Los Angeles Times Book Prize for science and technology and was a New York Times bestseller.
Determined
The sequel in argument to Behave: if every act follows from biology and circumstances nobody chose, Sapolsky says, there is no free will, and no one deserves blame or praise. He makes that case, including why chaos theory and quantum physics do not rescue free will, then asks how justice and punishment would work without it. It was a New York Times bestseller and drew wide criticism from philosophers.
In What Order to Read Robert Sapolsky
None of his books depends on another, but they fall into three groups: the stress books (Why Zebras Don’t Get Ulcers and the academic monograph before it), the lighter books (two essay collections and the baboon memoir), and the two big late books, Behave and Determined.
Read Behave before Determined. The later book takes the evidence of the first as given and draws the conclusion about free will from it, so it makes more sense once you have seen that evidence laid out. Stress, the Aging Brain, and the Mechanisms of Neuron Death is a scientific monograph and is only for readers who want the research behind the stress books.
A reading path
1. Why Zebras Don’t Get Ulcers (1994)
2. A Primate’s Memoir (2001)
3. The Trouble with Testosterone (1997)
4. Behave (2017)
5. Determined (2023)
The years · 1957–2023
Quick facts about Robert Sapolsky
- Known for
- Robert Sapolsky is known for his research on how stress hormones affect baboons and the brain, and for arguing, in Behave and Determined, that human behaviour is fully the product of biology and circumstance, with no room for free will.
- 1957
- Born in Brooklyn, New York
- 1978
- First season with the baboons in Kenya
- 1987
- MacArthur Fellowship
- 2017
- Behave
- 2023
- Determined
- Born
- 6 April 1957, Brooklyn, New York, to an Orthodox Jewish family of immigrants from the former Soviet Union
- Education
- BA in biological anthropology, Harvard (1978); PhD in neuroendocrinology, Rockefeller University
- Position
- John A. and Cynthia Fry Gunn Professor of biology, neurology and neurosurgery, Stanford University
- Fieldwork
- About 25 years studying a wild baboon troop in Kenya; research associate of the National Museums of Kenya
- Honours
- MacArthur Fellowship (1987); Los Angeles Times Book Prize for Behave (2017)
- Family
- Married to the neuropsychologist Lisa Sapolsky; two children
The red mark is 2017: Behave, his book on the biology of human behaviour, which won the Los Angeles Times Book Prize.
How Robert Sapolsky Writes: From the Neuron to Evolution
Sapolsky writes from his own research. Why Zebras Don’t Get Ulcers grows out of his lab work on glucocorticoids and the brain, and the baboons in A Primate’s Memoir are the same animals whose stress hormones he measured in Kenya. In a 2004 paper in PLOS Biology he and Lisa Share described how one troop, Forest Troop, became markedly less aggressive after tuberculosis killed its most aggressive males, and how the new males that joined later took on the calmer culture.
His big books are built on a fixed structure. Behave takes one behaviour and moves outward in time, from the second before it to the evolution of the species, bringing in endocrinology, psychology, anthropology and genetics along the way; The Guardian called it “a miraculous synthesis of scholarly domains”. Reviewers of his memoir and essays point above all to the jokes: The New York Times praised the comedy of A Primate’s Memoir.
He does not hedge his conclusions. Determined states plainly that free will does not exist and goes on to ask what should follow for blame and punishment. That directness is also where critics push back: even reviewers who liked the book, in Science and The Atlantic, said it does not engage enough with philosophers’ arguments, including the view that free will is compatible with determinism.
Watch
Introduction to Human Behavioral Biology
The opening lecture of Sapolsky’s Stanford course Human Behavioral Biology, recorded in 2010, in which he sets out how he approaches human behaviour through biology.
Frequently asked questions about Robert Sapolsky’s books
How many books has Robert Sapolsky written?
Seven: Stress, the Aging Brain, and the Mechanisms of Neuron Death (1992), Why Zebras Don’t Get Ulcers (1994), The Trouble with Testosterone (1997), A Primate’s Memoir (2001), Monkeyluv (2005), Behave (2017) and Determined (2023). Junk Food Monkeys is the British title of The Trouble with Testosterone, not a separate book.
What are Robert Sapolsky’s books in order?
Stress, the Aging Brain, and the Mechanisms of Neuron Death (1992), Why Zebras Don’t Get Ulcers (1994), The Trouble with Testosterone (1997), A Primate’s Memoir (2001), Monkeyluv (2005), Behave (2017) and Determined (2023).
Where should I start with Robert Sapolsky?
With Why Zebras Don’t Get Ulcers, his guide to stress and stress-related disease, which comes straight out of his own research. If you prefer a story, start with A Primate’s Memoir, about his years with the baboons in Kenya.
What is Robert Sapolsky’s most famous book?
Behave: The Biology of Humans at Our Best and Worst (2017). It won the Los Angeles Times Book Prize for science and technology and was a New York Times bestseller. Why Zebras Don’t Get Ulcers is his best-known earlier book.
Should I read Behave or Determined first?
Behave. Determined builds on its evidence about how biology and circumstance shape behaviour, and uses it to argue that free will does not exist.
Why is Determined controversial?
Because it argues that free will does not exist and that nobody truly deserves blame or praise. Several philosophers and critics, including Kieran Setiya in The Atlantic, John Martin Fischer in Notre Dame Philosophical Reviews and Jessica Riskin in The New York Review of Books, said it treats a philosophical question as a purely scientific one and does not engage with the view that free will is compatible with determinism. Other reviewers, in the Los Angeles Times and The Wall Street Journal, praised its research and writing.
What prizes has Robert Sapolsky won?
Behave won the Los Angeles Times Book Prize for science and technology for 2017, and A Primate’s Memoir was nominated for the Aventis Prize for Science Books in 2002. He received a MacArthur Fellowship in 1987.
What happened to Sapolsky’s baboons?
In 1983 tuberculosis, traced to infected meat in a tourist lodge’s garbage dump, killed the males of his Forest Troop that fed there, the most aggressive ones. The surviving troop became noticeably more peaceful, and the males who joined it in later years adopted that behaviour. Sapolsky and Lisa Share reported this in PLOS Biology in 2004.
Is Robert Sapolsky still alive?
Yes. He was born on 6 April 1957 in Brooklyn, New York, and is a professor at Stanford University.
Can I watch Robert Sapolsky’s lectures?
Yes. Stanford has published his undergraduate course Human Behavioral Biology, recorded in 2010, free on YouTube. He also appears in the National Geographic documentary Stress: Portrait of a Killer (2008).
Footnotes
- Robert Sapolsky — Wikipedia
- Determined: A Science of Life Without Free Will — Wikipedia
- Los Angeles Times Book Prizes 2017 — Bookreporter
- A Primate’s Memoir — Kirkus Reviews
- A Pacific Culture among Wild Baboons — PLOS Biology, 2004
- Stanford scientist, after decades of study, concludes: We don’t have free will — Los Angeles Times, 2023
Bibliography last verified 9 October 2026. Where sources give different first-publication years, this page uses the year in library catalogues or the publisher’s own record.
This list was not put together by a machine.
The notes are all mine,
and the books are all his.
Lisanne x
Written by Lisanne Swart, who has curated reading lists and author guides at lisanneswart.com since 2021.
See more on her personal bookshelf.
“We’ve got no free will. Stop attributing stuff to us that isn’t there.”
— Robert Sapolsky, interview with the Los Angeles Times (2023)
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