Do Turtles Get Cancer?
SMJ Mortazavi
Professor of Medical Physics, Shiraz University of Medical Sciences (SUMS)
A brilliant new paper in BioScience explores this compelling question — and adds another piece to the puzzle of Peto’s Paradox. The development of multicellularity necessitated the ability to suppress cancer. Since each cell carries some likelihood of becoming cancerous, larger and longer-lived organisms would theoretically face a higher risk of developing cancer compared to smaller, shorter-lived ones. However, this expected correlation between body size and cancer risk does not hold true, a phenomenon referred to as Peto's paradox. Remarkably, animals with cell counts 1,000 times greater than humans do not experience higher cancer rates, indicating that natural mechanisms in these organisms are capable of suppressing cancer far more effectively than those in human cells.
Read the article: https://academic.oup.com/bioscience/advance-article/doi/10.1093/biosci/biaf100/8185759
Despite their large bodies and extreme lifespans, turtles rarely get cancer. Drawing on zoo necropsies, pathology data, and molecular evidence, the authors reveal that turtles exhibit remarkable resistance to oxidative stress and protein damage — traits that may underlie their natural tumour suppression. This makes them a promising, yet underexplored model in longevity and cancer research.
As a team working at the interface of environmental biology, evolutionary medicine, and cancer epidemiology, we’ve been exploring these paradoxes for years. Our previous work questioned the simplistic notion that cancer is just “a matter of random mutations.” Instead, we see carcinogenesis as a systems-level phenomenon, shaped by:
- Evolutionary pressures (e.g., why whales don’t get more cancer than humans) https://pubmed.ncbi.nlm.nih.gov/39027707/
Compared to tutles, humans serve as a superior model. An excellent approach would involve studying the mechanisms of resistance to radiation-induced cancers in regions where natural radiation levels exceed those found on the surface of Mars.
- Environmental exposure and human adaptability (e.g., the adaptive response seen in Ramsar residents exposed to high background radiation — Health Physics, 2002), Health Physics 82(1):p 87-93, January 2002., Health Physics 122(4):p 508-512, April 2022. | DOI: 10.1097/HP.0000000000001521
- Comparative models from nature (as discussed in Dr. James Welsh’s book - Sharks Get Cancer, Mole Rats Don’t) https://www.thelancet.com/journals/lanonc/article/PIIS1470-2045(16)30459-4/abstract
- Population-level traits (like our recent work probing the nuanced association between breast size and breast cancer risk, moving beyond correlation to causal complexity — JBP&E, 2025). https://pubmed.ncbi.nlm.nih.gov/39975528/
Cancer resistance in nature isn’t just a curiosity — it’s a blueprint for innovation in oncology. Turtles, elephants, naked mole rats, and even humans in extreme environments all point to one truth: The fight against cancer must be informed by biology, environment, and evolution.
How can we better integrate insights from natural models into mainstream cancer research?
Selected References:
Mortazavi SMJ, Zare O, Ghasemi L, Taghizadeh P, Faghani P, Arshadi M, Mortazavi SAR, Sihver L. A Reexamination of Peto's Paradox: Insights Gained from Human Adaptation to Varied Levels of Ionizing and Non-ionizing Radiation. J Biomed Phys Eng. 2024 Jun 1;14(3):309-314. doi: 10.31661/jbpe.v0i0.2402-1729. PMID: 39027707; PMCID: PMC11252545.. https://lnkd.in/eaXQpmay
Faraz M, Nematollahi S, Tahmasebi S, Welsh JS, et al. The Association between Breast Cup Size and Breast Cancer Incidence: Insights from a Global Dataset. J Biomed Phys Eng. 2025. doi: 10.31661/jbpe.v0i0.2412-1869. https://lnkd.in/gsAPQAge
Sharks Get Cancer, Mole Rats Don't, Cancer and SocietyBooks, Volume 17, Issue 10p1359October 2016
#PetoParadox #ComparativeOncology #CancerResearch #LongevityScience #EvolutionaryMedicine #Turtles #RadiationBiology #BioScience2025 #Ramsar #BreastCancer #HBRAs #CupSize
Medical Physicist | MSc Graduate – SUMS Researcher, Ionizing & Non-Ionizing Radiation Research Center
3moThat’s a fascinating question! It also makes me wonder whether the turtle’s microbiome — on its shell, skin, or gut — might contribute to its remarkable cancer resistance by producing anti-tumor metabolites. Could this be an overlooked factor in Peto’s Paradox?