Nature and nurture

Professor Marlene Zuk’s newest book dives in to the debate about what drives behavior.
November 10, 2022

In her latest book, Dancing Cockatoos and the Dean Man Test, Marlene Zuk, illuminates how all our attributes, behavior or not, are shaped by both genes and the environment, in a complex way that defies a simple binary. She shared her thoughts on the topic as well as writing about science.

What was the impetus for this book?
Most if not all of my books are about genes, evolution, and behavior, and this one is no different. I suppose you could ask why I keep writing the same thing over and over, but I assure you each one takes a separate tack on this very large subject. In this book, I became fascinated with the way that we keep coming back to the nature-nurture debate, no matter how many times we think we have resolved it. The minute I describe a behavior in an animal, the first thing people want to know is whether that behavior is instinctive (or genetic, or hard-wired, or a number of other synonyms), or whether it is learned (or cultural or flexible). We know it isn’t really a dichotomy—all traits are both—but the nature-nurture debate has become what you might call a “zombie” idea, one that we can try to kill but that just keeps resurrecting itself.

What do you think people get wrong about behavior and why and how it evolves?
First, people think behavior is special, or different from other characteristics like the physical body or physiology. You don’t get particularly worked up about whether your liver is the size that it is because of your environment or your genes (news flash, it is a bit of both). But ask about a trait like sexual orientation or intelligence, and people are very invested in claims that it’s all one or the other. Again, it’s both. Second, it’s tempting to see behavior evolving for a purpose—“we needed to communicate, so we evolved language” (or bees evolved dancing). But evolution doesn’t have a goal, and it doesn’t march along improving organisms, those funny—and inaccurate—cartoons showing the fish moving out of the water followed by a reptile, an ape, and finally a person notwithstanding.

The book explores the intersection of nature and nurture. What are some of the unexpected ways behavior has evolved in response to that interaction?
Because I’m arguing that all behavior, like all other traits, evolves because of interaction between genes and the environment, you might say that whatever behavior you find unexpected is an example of that interaction. Some of my favorite examples have to do with parasite manipulation of host behavior. For instance, a one-celled parasite called toxoplasma has to get into both a rodent and a carnivore, like a cat, to complete its life cycle. Mice infected with toxoplasma change their behavior and become more reckless around predators, increasing their likelihood of being eaten.

This is your fifth popular science book. How has your approach to communicating science evolved since you started doing this?
I think of my writing as a scholarly endeavor on its own, rather than me “dumbing down” facts for the general reader. People don’t want someone to translate a jargony scientific paper into words of one syllable, they want to understand the importance and wonder of the natural world.