Science writer Carl Zimmer explores the complexities of heredity in She Has Her Mother’s Laugh (Dutton, June).
You’re a science journalist at a time when science seems to be under attack. How does this affect your work?
I’m always prepared for a story I write to generate a lot of pushback, regardless of the fact that the science I’m reporting on is rock solid. It is overwhelmingly clear that modern humans originated in Africa, for example, and that Europeans 10,000 years ago had dark brown skin. But judging from Twitter, some people can’t stand hearing that. I don’t shy away from these controversies; instead, I try to use them as an opportunity to show readers how scientists know what they know.
The book describes both historical abuses and cutting-edge advances in the field of heredity. Were some topics more difficult to write about than others?
There are an overwhelming number of stories in the history of heredity, so picking out the best ones for my book took a lot of research. Some of these stories chronicle the brilliant insights that helped us understand the nature of heredity. But to pretend that there was no dark side to this work would be to ignore history. In either case, I looked for the stories that I could tell with the richest human detail.
You argue that heredity extends far beyond genes. Does that mean genes don’t matter?
Definitely not. The genes we inherit can influence us in all sorts of ways—not just the color of our eyes, but our personalities and our skills. And I think we need to be much more skeptical about other forms of heredity, like epigenetics. There’s a huge excitement over the possibility that the experiences of parents alter the heredity of future generations. That seems to be true for plants, but the evidence for us is incredibly thin.
You write that we each have an “inner heredity.” Why should we think of our own bodies that way?
Each of us starts out as a single cell and ends up as over 30 trillion cells—muscle cells, neurons, liver cells, and more. Each of those cells inherited the genes, and much more, from that original cellular ancestor. Tracing that genealogy in our bodies is one of biology’s big challenges today—and it could help doctors come up with new ways to treat all sorts of diseases in which that genealogy goes awry.
What was the most surprising thing you learned while working on this book?
I was surprised by how so many animals have to inherit bacteria from their ancestors in order to survive. Cockroaches, for example, carry bacteria that have to infect their eggs so that the next generation can use them to survive. It’s a parallel kind of heredity happening all around us—and maybe even inside us, too.