An Interview With Carl Zimmer

“Heredity is a lot more complex than most people think. In She Has Her Mother’s LaughNew York Times columnist Carl Zimmer dives deep into the ways that we pass along our genetic inheritance. Through history, science, and a boatload of personal curiosity (the book originated from questions he had regarding his own child, and he had his entire genome mapped in the process of writing it), Zimmer seeks to retell the story of heredity in broader and more inclusive terms than the ones we’re used to hearing. For example, who we become is determined by our ancestors’ genes, yes; but it is also a product of our own cells—for one cell can contribute to millions of future cells. How we treat ourselves, what we learn, and even how we feel, eventually contributes to our hereditary future. The forces at work are myriad, mostly unseen, and subject to variables that we barely understand. Zimmer is trying to help us here, to teach us, and in doing so he succeeds in entertaining us as well. –Chris Schluep, Amazon Book Review”

I interviewed Carl with some questions about the book, and here are our interview questions:


Armen: Leaders of the past don’t appear wise with regards to attempts to continue their bloodline, with inbreeding leading to genetic defects. What is an example of something done today in genetic research or modification that may turn out to be just as shortsighted?

Carl Zimmer: I think that genetic modification of crops has the potential to bring tremendous benefits to humanity. But there are many ways in which it could fail. We’ve already witnessed one such failure, which came about because we didn’t respect the power of evolution. Many crops have been engineered with resistance to glyphosate, so that farmers can then use glyphosate more effectively to kill weeds rather than crops. The thinking behind this strategy, as far as I can discern, was based on the assumption that weeds could never evolve resistance to glyphosate–only engineering could achieve that. Well, we ran that experiment. And we were wrong. Because farmers only used glyphosate on their fields, they created a very strong benefit to any mutation that offered any resistance to the herbicide. In a matter of years, natural selection produced weeds so resistant to glyphosate that the herbicide is useless against them. Now GM crop producers are offering new plants engineered to resist a different pesticide, Dicamba, but we should not assume that now, at last, we have escaped evolution.

Armen: Is there any path for Jennifer Doudna and the CRISPR researchers that doesn’t involve continuous editing to the point of rewritten code like programming languages?

Carl Zimmer: I expect that for the foreseeable future, CRISPR will be used to make a few tweaks to DNA at most. It will be used to try to fix single-mutation genetic disorders like sickle cell anemia, for example, or to change the flowering time of tomatoes by altering a single genetic switch. Scientists don’t know how to reliably and safely make lots of edits to DNA at once. And we don’t know enough about genes to make useful changes on such a grand scale.

Armen: Like Watson and Crick stealing upon the research that Rosalind Franklin did, and getting the credit for it, will there be any credit given to those with certain genes that we will copy for the future, or will the desired traits become ubiquitous and no longer unique?

Carl Zimmer: It’s possible. Helen Hobbs, a scientist at professor at the University of Texas Southwestern Medical Center, and her colleagues discovered a mother and daughter in Texas with a rare mutation to a gene called PCSK9 that leads to very low cholesterol. That discovery then led to the invention of drugs that may be able to dramatically reduce the risk of heart disease. If society came to accept editing the DNA of embryos to reduce chronic diseases, I could imagine they might put PCSK9 on their list.

Armen: In the same way that Mexicans broke people down into colors types such as mestizo and mulatto, does heredity continue the separating of every single trait into a hierarchy?

Carl Zimmer: Social hierarchies are social constructions. I inherit traits–and the DNA for those traits–from thousands of ancestors who lived across Europe and the Near East, whose ancestors, in turn, lived in Africa. What category people put me in because of that genetic melange has no deep biological meaning–it’s a product of our culture.

Appreciations to Carl for taking part in the interview. You can find more material from Carl at these locations:

Matter, a weekly science column for the New York Times
She Has Her Mother’s Laugh, a book about heredity. (“Magisterial”–The Atlantic)
Friday’s Elk, a weekly newsletter
More information at

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