Greenland sharks are known for having a lifespan of nearly 400 years. They can grow up to 20 feet in length and weigh over 1,400kg. This shark species inhabits the deep waters of the North Atlantic and Arctic Oceans and has been a scientific mystery. Now a study has shed light on the reason for their long lives, without any tumours and cancers.

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Science suggests that the longer an organism's lifetime, the higher the chances of it getting cancer. Accumulation of damage to DNA causes cancer, and since animals with longer lifespans have more cells, the chances of cell division going wrong increase.

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However, in the case of Greenland sharks, this theory has not held true, also known as Peto's paradox.

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How do Greenland sharks live a healthy, long life?

The team of scientists mapped the Greenland shark's complex genome and got some answers to the paradox. They studied a class of genes within the shark’s genome that is involved in the regulation of a key immune system protein. They found that the Greenland shark has enhanced DNA damage response and repair mechanisms.

The study noted that these gene families activate the protein NF-kB which helps regulate inflammation, immunity, and cell survival. These mechanisms are involved in suppressing tumours and cancers. What further helped the Greenland sharks was the fact that they had more copies of these genes compared to other short-lived shark species. This kept their genome more stable and prevented damage.

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“These genomic analyses offer new insights into the molecular basis of the exceptional longevity of the Greenland shark and highlight potential genetic mechanisms that could inform future research into longevity,” scientists wrote in the study.

They are also at a lower risk of infectious diseases and autoimmune problems because of their "robust immune defence". 

Living in the depths of the ocean, the Greenland sharks adapt to a slow life in the dark. The eye protein rhodopsin helps them with this and makes them more adept at processing blue-light wavelengths.