An Animal’s Size And Its Cancer Risk | Bastetodon, A 30 Million-Year-Old Apex Predator

Mar 4, 2025

Dr. Sarah Amand, an Associate Professor at Johns Hopkins, challenges Peto's Paradox, which maintains that larger animals don’t have higher cancer risk. She reveals fresh findings suggesting that larger species might actually face increased cancer rates. The conversation also explores the fascinating traits of cancer-resistant animals like elephants. Additionally, a remarkable fossil of Bastetodon, a 30-million-year-old predator, is unveiled, connecting ancient ecological dynamics to cultural history.

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INSIGHT

Peto's Paradox Challenged

Peto's Paradox, an observation by Richard Peto, stated that larger animals don't have higher cancer risks than smaller ones.
New research challenges this paradox, finding that larger species actually show a greater cancer prevalence.

INSIGHT

Zoo Data Challenges Paradox

A new study using zoo death reports reveals Peto's Paradox may be false.
Larger species demonstrate an increased cancer prevalence, contrary to the paradox.

ANECDOTE

Elephant Cancer Resistance

Elephants, despite their size, exhibit some cancer resistance.
They possess multiple copies of the P53 tumor suppressor gene, offering higher protection.

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A study finds that Peto’s Paradox, which states that larger animals are no more likely to get cancer than smaller ones, may not hold up. Also, a nearly complete predator skull was found in the Egyptian desert. Its lineage indicates that it was a top carnivore of the age.

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

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.

Meet Bastetodon, A 30 Million-Year-Old Apex Predator

Once upon a time, some 30 million years ago, what is now Egypt’s Western Desert was a lush forest. Humans had not evolved yet, the nearest relatives being monkey-like creatures. And through those forests stalked Bastetodon syrtos, a newly described apex predator from an extinct lineage known as the Hyaenodonts—one of the top carnivores of the age.

Researchers recently discovered a nearly complete skull of the creature. They reported on the find in the Journal of Vertebrate Paleontology. Host Flora Lichtman talks with Shorouq Al-Ashqar of the Mansoura University Vertebrate Paleontology Center about the discovery, and the picture it helps paint of ancient life.

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