New research overturns a 45-year-old belief that an animal's size does not affect its cancer risk, showing that larger animals such as elephants and giraffes have higher cancer rates than smaller animals. The study also found that species that quickly evolved into large animals, such as elephants, developed stronger natural defenses against cancer, with some species experiencing unexpected rates of cancer.
Large animals face a higher risk of cancer, but some, like elephants, have evolved strong defenses. Understanding these defenses could lead to breakthroughs in cancer research.
A new study challenges long-held beliefs about cancer in the animal kingdom, revealing that large animals such as elephants, giraffes and pythons have higher cancer rates than smaller animals such as mice, bats and frogs.
Researchers from the University of Reading, University College London and Johns Hopkins University School of Medicine analyzed cancer data from 263 species across four major animal groups: amphibians, birds, mammals and reptiles. Their findings contradict "Peto's Paradox." "Peto's Paradox" is a theory proposed in 1977 that holds that an animal's size has nothing to do with its risk of cancer.
The study, published in the Proceedings of the National Academy of Sciences, found that larger animals have consistently higher rates of benign and malignant tumors. However, larger animals that have evolved more quickly, such as elephants, have also developed greater natural resistance to cancer.
Professor Chris Venditti, senior author of the study from the University of Reading, said: "Everyone knows the myth that elephants are afraid of rats, but when it comes to cancer risks, rats are less scary. We have shown that large species like elephants do face higher rates of cancer - which is what you would expect because they have more cells that can go wrong."
The study analyzed the largest data set of its kind to date. The researchers studied cancer records in 31 species of amphibians, 79 species of birds, 90 species of mammals and 63 species of reptiles dissected by veterinarians. They used advanced statistical methods to analyze the relationship between cancer incidence and body size, taking into account the evolution of different species.
They looked at birds and mammals, which stop growing at a certain size, and amphibians and reptiles, which grow throughout their lives. Although there are differences in growth patterns between the two groups of animals, the overall trend is the same - larger species have higher rates of cancer. However, research shows that species that have rapidly evolved to large sizes within short evolutionary timescales, such as elephants, have evolved better mechanisms to control cell growth and prevent tumors. For example, elephants have about the same risk of cancer as tigers, which are only one-tenth the size of elephants.
Co-author Dr Joanna Baker from the University of Reading added: "When species need to get bigger, they also evolve extraordinary defenses against cancer. Elephants should not be afraid of their size - they have developed sophisticated biological tools to control cancer. This is a beautiful example of how evolution can find solutions to complex challenges."
It's difficult for modern medicine to know exactly how humans adapted to this body type-cancer pattern. The study shows a general trend of higher cancer rates in larger species, but also reveals how some species evolve better cancer defenses as they increase in size. Together, the findings support the idea that superior cellular defense mechanisms - such as improved control of cell growth - evolved at specific points in time and in larger species. This opens a new door to understanding cancer mechanisms, potentially providing new insights into human disease and its treatment.
On average, larger species have more cancers than smaller species. However, the researchers also found a subset of species with cancer rates that were much higher or lower than expected for their size. For example, researchers found that the common budgerigar (Melopsittacus undulatus) has cancer rates that are more than 40 times higher than expected for its size of less than 30 grams. In contrast, almost no cancer incidence has been documented in naked mole rats (Heterocephalusglaber).
Dr George Butler, lead author of the study, from University College London and Johns Hopkins University, said: "Discovering which animals are naturally better at fighting cancer opens up exciting new avenues for research. By studying these successful species, we can better understand how cancer develops and potentially discover new ways to fight cancer. This could lead to breakthrough treatments in the future."
Compiled from /ScitechDaily
DOI:10.1073/pnas.2422861122