Larger species do develop more cases of cancer

A study has debunked a 45-year-old belief about cancer in the animal kingdom, showing that larger species such as elephants and giraffes have higher rates of cancer than smaller ones such as mice or frogs. The research, by experts from the University of Reading , University College London (UK) and Johns Hopkins University (USA), analysed data on cancer in 263 species of amphibians, birds, mammals and reptiles. The findings challenge the “ Peto paradox ”, which suggested there was no relationship between an animal’s size and its risk of cancer.

The study, published in PNAS , showed that larger animals have a higher prevalence of benign and malignant tumors. However, species that evolved quickly to grow, such as elephants, developed natural defense mechanisms against cancer.

For example, an elephant has about the same risk of cancer as a tiger, despite being much larger . Researchers also found exceptions, such as the budgerigar, which has much higher cancer rates than expected for its size, and the naked mole rat, which has almost no cancer.

Carlo Maley, director of the Arizona Cancer Evolution Center (USA), highlights the relationship between the evolution of body size and defenses against cancer, although he suggests that an increase in body size may need time for an adequate defense to evolve. He also points out that, although the study suggests that larger animals may have more cancer, the relationship is not as strong as expected.

Frédéric Thomas and Antoine Dujon of the CNRS consider the study to be a valuable analysis, although they acknowledge that statistical choices and data heterogeneity may affect interpretation. Overall, they believe that research into the relationship between body size and cancer is promising, but that further exploration of the underlying molecular mechanisms is needed.

In summary, although the study supports the relationship between body size and cancer prevalence, further studies and analyses are needed to validate the findings and understand the evolutionary defense mechanisms against cancer.