Article content continued

Dr Vincent Lynch, the study author, said: “A major constraint on the evolution of large body sizes in animals is an increased risk of developing cancer.

“If all cells have a similar risk of malignant transformation an organism with many cells should have a higher risk of developing cancer than organisms with fewer cells. Organisms with long lifespans have more time to accumulate cancer-causing mutations than organisms with shorter lifespans and therefore should be at an increased risk of developing cancer.”

However elephants do not face an increased risk of cancer — a discovery dubbed “Peto’s Paradox” named after Sir Richard Peto, the Oxford University scientist who found that the incidence of cancer does not correlate with the number of cells in an organism.

These results suggest that an increase in the copy number of TP53 may have played a direct role in the evolution of very large body sizes

Now scientists believe they know why. Elephants are the first species found to have 20 copies of the TP53 gene, which stops cancer growth by spotting when cells are damaged.

“These results suggest that an increase in the copy number of TP53 may have played a direct role in the evolution of very large body sizes,” added Dr Lynch.

The researchers hope it may now be possible to use this newly discovered protein to develop new treatments that can help stop cancers from spreading or even developing in the first place.

Dr Lynch said: “It may be possible to develop a drug that mimics the function of the TP53 gene. The next steps are to figure out precisely how these extra copies are working in the cell, and if there are other genes with elephant-specific changes evolved in their cancer resistance.”

The research was published on the online science network BioRxiv.