Why Whales and Dolphins Don’t Get Cancer: The Surprising Truth

Whales and dolphins are some of the longest-living creatures in the animal kingdom. The average life expectancy for whales ranges from 50 to 100 years, depending on the species. Killer whales, which live in the ocean, can reach an age of up to 90 years old. It is not uncommon for them to outlive humans by decades! Similarly, many species of dolphins have been known to survive into their 70s or 80s. Some research has even suggested that certain types of dolphins may be able to live up to 200 years! These incredible lifespans make it all the more remarkable that whales and dolphins don’t get cancer as many mammals do, a phenomenon scientists are still trying hard to understand.

Why Whales and Dolphins Don’t Get Cancer

Cetaceans like whales, dolphins, and porpoises are the largest and longest-living mammals, and they have the remarkable ability to resist cancer. Scientists have long been puzzled by this phenomenon, known as Peto’s Paradox, which suggests that organisms with more cells should have a higher risk of developing cancerous mutations. A recent study has discovered that cetaceans have genes that rapidly evolve to suppress tumors.

An international group of researchers from Britain, Chile, and the United States investigated how natural selection led to the development of 1077 tumor suppressor genes in the whale and dolphin lineage. To compare, they looked at those same genes in 15 other mammalian species, including humans. It was discovered that the rate at which the genes mutated and were gained or lost was nearly 2.4 times higher in cetaceans than in other mammals — most notably in baleen whales (which include blue, humpback, and right whales).

The research suggests that whales and dolphins don’t get cancer because of genetic characteristics which may also cause them to grow larger and live longer. The study revealed that there were signs of positive selection in genes that control DNA damage, tumor growth, and immunity. In addition, 71 genes related to cancer prevention and 11 genes connected to longevity were found to have been duplicated. Taken together, these results suggest that natural selection has favored whales and dolphins with genetic traits that help them fight cancer and live longer lives.

Do Other Big Animals Get Cancer?

Well, elephants don’t. And they are certainly big. Not as big as a blue whale, but big enough.

Elephants are the largest land mammal and can grow to be up to 13 feet tall at the shoulder. They weigh between 4,000 and 14,000 pounds, depending on their species. African elephants typically have larger bodies than Asian elephants, while Indian elephants tend to have smaller frames. They are highly intelligent animals that live in tight-knit family groups and communicate with each other through a variety of sounds, smells, body language, and physical gestures. In addition to being incredibly large creatures with impressive intelligence levels, they also demonstrate remarkable longevity—many living well into their 60s or 70s. Despite this incredible size and lifespan, though, it appears that cancer is relatively rare among elephant populations.

Why Don’t Elephants Get Cancer?

For elephants, a plausible explanation as to why they don’t get cancer may be attributed to the gene known as p53. Elephants possess 20 copies of this gene, whereas humans and most animals only have one, which produces two proteins. A new study from Molecular Biology and Evolution looks into how elephants’ multiple copies of the gene provide cancer-fighting benefits that can help both elephants and humans. This research also opens up the potential for further exploration into how cells defend themselves against a damaged genome.

Mammals rely on a gene called p53 to protect them from developing cancer. In humans, this gene has been damaged in over half of all cancers. Scientists studied the 40 copies of the p53 gene in elephants and found two ways it helps them avoid cancer. The multiple copies lower the risk of mutations occurring, and the different triggers they respond to better detect and remove mutated cells.

These extraordinary discoveries suggest that elephants possess various methods to utilize p53. This opens up the potential for scientists to develop useful strategies in humans to prevent cancer. Scientists are currently examining an African elephant at the Vienna Zoo to assess how its p53 proteins interact with altered cells and other relevant molecules and plan to contrast those results with findings from human cells. This is an unexpected yet valuable source of information for people studying how cells react to DNA damage.

Did Big Dinosaurs Get Cancer?

A study published in The Lancet Oncology in 2020 discovered that even massive dinosaurs were susceptible to cancer. Evidence of this was found in a 76 million-year-old centrosaurus fossil from Alberta, Canada, that had osteosarcoma, a tumor similar to those found in humans. Its bone resembled a human fibula that had been inflicted with the same form of cancer.

At first, scientists assumed that the odd shape of a fossil was a result of a broken bone that had not healed properly. However, a recent research project compared the internal structure of the fossil with a bone tumor from a human to determine the cause of the odd shape. The results of the study showed that the dinosaur had osteosarcoma, a type of cancer that normally affects teenagers and young adults. This condition causes tumors of immature bone tissue, usually located in the bones of the legs.

The findings from the researchers are groundbreaking, as it is the only time that cancer has been identified at a cellular level in dinosaur fossils. Previous studies have found benign cancers in fossilized Tyrannosaurus rex bones and advanced arthritis in duck-billed hadrosaurs, and a diagnosis of osteosarcoma in a 240-million-year-old turtle. However, these discoveries have been unable to confirm a diagnosis of cancer at the cellular level until now. The research team’s results open up new possibilities for further study into how dinosaurs may have developed cancer and what this can tell us about our own development and future health implications.

Experts, such as radiologists, surgeons, pathologists, and paleontologists, studied the structure of cells in fossils using computerized tomography imaging and narrow sections under a microscope. They noticed tumors had advanced enough to likely have caused the animal’s death in a similar case with a human. However, since the fossil was found in a bone bed containing several Centrosaurus specimens, the dinosaur likely perished in a flood event like the rest of its herd instead of cancer. The researchers suggest that close examination of peculiar fossil deformations with modern imaging and diagnostic methods could bring forth new discoveries about the evolutionary beginnings of illnesses.

Are There Any Other Animals That Don’t Get Cancer?

Despite their unappealing appearance and subterranean lifestyle, naked mole rats possess a trait that many other creatures, including humans, envy: they never suffer from cancer. Recently, scientists uncovered the source of the rodent’s superior health. A complicated sugar that prevents cells from clumping together and forming tumors.

Naked mole rats have a remarkable ability to resist cancer, and scientists are trying to reproduce this trait artificially. A study has revealed that this is due to the presence of a polymer called hyaluronan, which helps to control the growth and mechanical strength of cells. When hyaluronan was removed from the naked mole rats, cancer was allowed to spread as normal. They have five times more of this polymer than humans do.

Researchers believe that enhanced amounts of hyaluronan in the skin of the naked mole rat could be the cause of their cancer resistance and extended life span. While the similarities between humans and these creatures are limited, the study results could still be beneficial in helping to create treatments and cures in the future.

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