Geneticists reveal how whales became giants

(ORDO NEWS) — Of all modern animals, none can compare with whales – giant marine mammals, reaching almost 200 tons in weight. And now geneticists have figured out how they got so big.

The evolutionary history of whales began about 50 million years ago, when their ancestors, medium-sized ungulate predators the size of a dog, roamed the land, and today among these animals are the largest creatures on Earth, reaching 33 meters in length and weighing over 150 tons.

However, such a gigantic size brings not only benefits, such as passive protection from predators or the ability to go without food for a long time: large animals grow slowly and produce small offspring, and a long lifespan increases their risk of developing neurodegenerative diseases and cancer.

So what genes played a key role in why whales became giants?

A group of researchers from the University of Campinas (Brazil) performed a molecular and evolutionary analysis of nine candidate genes: five genes (GHSR, IGF2, IGFBP2, IGFBP7 and EGF) associated with the production of growth hormone, and four (NCAPG, LCORL, PLAG1 and ZFAT), responsible for the increase in body size in cows and sheep – land relatives of whales.

The researchers evaluated these genes in 19 species of whales, including seven that are over ten meters in length.

This made it possible to reveal signs of positive selection of the GHSR, IGFBP7, NCAPG, and PLAG1 genes in the evolutionary line of “giant” species. Apparently, it was these four genes that provided the whales with the ability to grow to enormous sizes.

Curiously, in addition to directly affecting the increase in body size, the GHSR and IGFBP7 genes were involved in the control of cell divisions and suppression of the development of cancerous tumors.

Thus, the work of these genes not only allowed whales to become huge animals, but also suppressed some of the unpleasant consequences of gigantism.

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