02/28/2025

What Does An Animal’s Size Have To Do With Its Cancer Risk?

Sub-adult African elephant male waling in the savanna. Grumeti, Western Serengeti. Serengeti National Park, Tanzania.
Credit: Shutterstock

If you throw a huge party, there’s more of a chance of problems than if you host a quiet get-together for a couple of friends. The logic is simple: Having more people around means more opportunities for chaos. Similarly, it would seem to make sense that in animals, a bigger species with more cells might have a greater chance of something going wrong with one of those cells, including mutations leading to cancer.

Back in 1977, a British epidemiologist named Richard Peto observed that that didn’t seem to be true. Bigger animals didn’t seem to have a greater risk of cancer than smaller ones. That became known as Peto’s Paradox, and has been a topic of debate among cancer biologists ever since.

Research published this week in the Proceedings of the National Academy of Sciences takes a new look at Peto’s Paradox using an unusual set of data—death reports from zoos around the world. Dr. Sarah Amend of Johns Hopkins Medical School joins Host Flora Lichtman to explain why, in their findings, Peto’s Paradox doesn’t seem to hold up—and what studying animal cancer rates could teach scientists about improving human health.


Further Reading


Donate To Science Friday

Invest in quality science journalism by making a donation to Science Friday.

Donate

Segment Guests

Sarah Amend

Dr. Sarah Amend is an associate professor of Urology and Oncology at Johns Hopkins University Medical School in Baltimore, Maryland.

Segment Transcript

The transcript of this segment is being processed. It will be available early next week.

Meet the Producers and Host

About Charles Bergquist

As Science Friday’s director and senior producer, Charles Bergquist channels the chaos of a live production studio into something sounding like a radio program. Favorite topics include planetary sciences, chemistry, materials, and shiny things with blinking lights.

About Flora Lichtman

Flora Lichtman is a host of Science Friday. In a previous life, she lived on a research ship where apertivi were served on the top deck, hoisted there via pulley by the ship’s chef.

Explore More