Behave: The Biology of Humans at Our Best and Worst

Author: Robert Sapolsky (wiki link).
Publishing year: 2017.

Humans are a violent species. At the same time, we hate the wrong kind of violence. This book attempts to explain our violent behavior. Even more, it highlights the meaning behind our aggressive tendencies.


The brain receives a lot of information at any given moment. For example, it simultaneously receives smells, sounds, visual images and environmental temperature. Additionally, the brain is processing internal information.

This multitude of stimuli contributes to making a behavior. Because of the complexity of this information and the way it interacts, we sometimes have reactions that are more autonomous than we might think. 

Girl throws stone in water. The same behavior means something else in a different context.
The same behavior means something else in a different context.

In order to understand how our personality was molded into behavioral patterns we need to take the journey back in time.

The Behavior Hypothesis

The hypothesis of the book is that there is no single cause for our behavior. One gene can not explain why we are violent. Furthermore, an isolated brain region cannot be singled out as responsible for our attitude. We can not point to a hormone, or to a single incident, nor past trauma. Finally, there is no single evolutionary mechanism that can explain our nature.

This can only be described and understood as multiple layers of causation.

Our behavior is complex and it can not be simplified to a single cause.

The Journey

In order to understand what causes behavior, the book takes us back in time on a journey of increasingly larger scales.

We start our exploration one second before the reaction occurs. Here we find the immediate triggers. But we need to go further: exploring what was happening minutes before the incident.

Next, we continue our journey back into the insight of behavior looking at the time span hours to days before the reaction occurred, where hormones  influence us. Further still, we go back to weeks and months. This is the timescale our brain can change due to our experiences. This is neuroplasticity in action.

Even further, we have to take the account of years. This takes us back to our adolescence and our developing years. Our decision center is also shaped by environment:

“Because is the last to mature, by definition the frontal cortex is the brain region least constrained by genes and most sculpted by experience. This must be so, to be the supremely complex social species that we are. Ironically, it seems that the genetic program of human brain development has evolved to, as much as possible, form the frontal cortex from genes”.

Finally, we reach the period when we were still developing in the womb, as an embryo. We have now traveled decades. At this scale epigenetic changes leave their mark on our personality. 

This journey explains how genes work in combination with the environment. We need to understand both in order to get a clear picture.

Going Further

Our personal journey backwards in time does not end at the moment of our conception. In order to understand how our personalities are shaped we need to understand our culture. We need to go back in time even further, centuries more. 

Study group of young students. Our behavior is shaped by multiple layers of causation.
Our response to one incident is already ingrained in our personality.

Finally, we need to go back millions of years, to be able to comprehend how evolution works. By shaping our genes, evolution has also shaped our behavior.

Robert Sapolsky is a neurologist and a primatologist. He explains violence as aggressiveness and conflict. At the same time being opposite to collaboration and empathy. Our reaction to an adverse situation depends on a myriad of things and they are all intertwined: hormones, muscles, brain, genes.

Buy the book on and support our website.

Back to Top