The great white shark accounts for about half of fatal shark attacks. But scientists think the ocean’s most fearsome predator could one day offer hope for saving human lives.
A team of scientists announced in recent days that they have cracked the genetic code of the great white, as a step toward unlocking the secrets of a species with a notorious reputation, an impressive resistance to genetic damage and a 500-million-year record of success.
“It’s really a miracle of evolution,” says the biologist Matt Hooper in the movie “Jaws,” where the great white made its ferocious debut in the public imagination. “All this machine does is swim and eat and make little sharks, and that’s all.”
But as real marine biologists know, that’s not all. The great white can cross the ocean. It can dive below 3,000 feet. It has a powerful sense of smell and the ability to detect other animals’ electric fields. And of great potential practical interest, its body heals wounds quickly and its cells resist the genetic damage that can lead to cancer.
“It’s famous or infamous, depending on how you look at it,” Mahmood Shivji, director of Nova Southeastern University’s Save Our Seas Foundation Shark Research Center and Guy Harvey Research Institute, one of the leaders of the project. “Its evolutionary design is pretty remarkable. These things get massive. They can cross ocean basins. They’re partially warm-blooded, which is quite rare in fishes. It can swim really long distances. It can dive down to at least 1,000 meters. And it’s one of the ocean’s apex predators. It’s really an evolutionary design marvel.”
Also leading the team were scientists from Cornell University and Monterey Bay Aquarium, with the discovery reported in the latest issue of the Proceedings of the National Academy of Sciences.
Although typically found in colder waters, such as the oceans off New England or California, great whites can be found off Florida. Last Sunday a group of spearfishermen encountered one off Jupiter and came back with video of the shark swimming lazily along the ocean floor. Although attacks on people are rare, great whites rank among the three most dangerous shark species, along with bull sharks and tiger sharks. Of the 160 recorded fatal shark attacks, they accounted for half, according to the International Shark Attack File.
It took scientists four years to decode the shark’s entire genome. With due respect to human beings, possessors of those big brains that produced the Sistine Chapel, quantum theory and “The Simpsons,” it’s apparently more complicated to build a saw-toothed shark that eats seals. The great white’s genome, which means its total amount of DNA, is 50 percent bigger than the human genome.
The shark’s genetic information will help conserve a species listed as “vulnerable” internationally. It will yield insights into their biology. And far down the road it could provide benefits to human health.
Great whites, given the nature of how they make their living, get into some violent encounters. But scientists have long observed that their wounds heal with impressive speed. In examining their genes, they found several that would account for this, including one involved with blood clotting.
Of potentially greater human significance, scientists have begun unraveling the genes that may help great whites prevent cancer. Large animals, because of the sheer number of cells in their bodies, should be at greater risk that cells will turn cancerous, Shivji said. This should be particularly true of species such as the great white, which can live 70 years or more, giving its cells ample time to develop cancer-causing mutations. But scientists suspect that sharks have a higher resistance to cancer than other vertebrates, and one reason may be the genetic mechanisms for preventing the DNA damage that produces cancer.
In great white, scientists found several genes that played roles in maintaining the stability of the genome, preventing the mutations that could lead to cancer or age-related diseases.
Will this ever help people fight cancer? No one knows, but there are practical steps that can be taken to find out.
These steps involve placing the shark genes in human cells in the laboratory, exposing the cells to carcinogens such as harmful chemicals and seeing if the shark genes offer any protection, Shivji said.
This effort will take years. Meanwhile, no one should take shark cartilage pills, which the U.S. Food and Drug Administration has labeled a fake cancer cure. Or eat sharks in hopes of gaining some sort of advantage over cancer. This just hurts shark populations while doing nothing for people.
“What we absolutely don’t want to do is encourage people to eat sharks,” Shivji said. “Thinking that eating sharks is going to cure cancer or other diseases is about as silly as thinking eating sharks is going to make you swim better or breathe underwater.”