And that process could potentially be sped up artificially.
"These mutations are already there, they just need to be spread out," said Mikhail Matz, an author of the study and a professor of biology at the University of Texas.
Giving coral evolution a boost isn't an entirely new concept. Some scientists have already suggested genetically modifying corals through artificial breeding, or doing the same for the tiny microbes that live inside corals and are essential to reef growth.
This study shows that human interventions may indeed be possible soon.
The team discovered the heat tolerance genes while cross-breeding individuals of a branching coral (Acropora millepora) located on the far northern Great Barrier Reef with members of the same species about 335 miles further south. Those from the northern part of the reef passed on the genes to their offspring, which had 10 times the normal survival rate when exposed to higher temperatures.
The researchers believe the coral larvae had altered genes working in the mitochondria — which power the cells and are inherited solely from mother corals. This discovery may lead to greater understanding of how cells in corals react to heat — and how best to protect them from it.
"The take-home message is that the genetic capacity is already there," Matz said.
Matz also believes this sort of polite evolution nudging may be applied to other marine animals -- such as other species of coral, sea urchins, sea cucumbers and maybe even fish.
For now, the researchers hope to push back coral extinction by shuffling adult forms of the species from one area to the next, which would require a permit from the Great Barrier Reef Park Authority.
But that won't be enough to secure the safety of the world's reefs. Rising temperature — we're talking about a two-degree change — is just one stress that coral has to face. They're also putting up with an increase in ocean acidification and greater threats of disease.
"It's not easy being a coral in the modern world," said Line Bay, a study author from the Australian Institute of Marine Science. "The challenge is to see if the winners of the heat are the winners under the other stressors."
The burning of fossil fuels has forced the oceans to absorb greater amounts of carbon dioxide, making the water more acidic and therefore making it difficult for corals to make calcium carbonate, the basic ingredient in building reefs.
Coral under higher stress throughout the world have recently undergone massive "bleaching events." When temperatures are too high or when corals are overexposed to sunlight, they expel the algae living in them and become a ghastly white. That doesn't mean they're dead, it just means they're sick and are less tolerant of diseases.
So far the researchers have only discovered genes that can be bred to raise corals' tolerance of heat, and they expect to come up with other "genetic markers" that would help the corals adapt.
In many parts of the world, including in the Caribbean Sea and Great Barrier Reef, coral cover has been cut in half since the 1970s, according to studies, and climate change is a primary culprit. That's important because reefs support quite a bit of the global economy — some $9.7 billion in tourism and $5.7 billion to fisheries — according to the National Oceanic and Atmospheric Administration.
Researchers warn, though, that as the oceans continue to heat up, the solution would only be temporary.
"Eventually, the corals will run out of genetic variation," Matz said. "But this might buy us time. We might feel safe for the next few decades."