On a remote island in Disko Bay, Greenland, a scientist in 1990 was collecting specimens of narwhals, the whales with unicorn-like tusks. He noticed an unusual skull on a hunter’s roof.

The teeth were bizarre: The top ones pointed forward. A couple spiraled out. They looked like a mix of narwhal and beluga, but with too many for a narwhal, too few for a beluga.

The hunter told the scientist that the skull had belonged to a strange animal he’d killed in the late 1980s. He had also killed two other similarly strange whales the same day. All had beluga-like flippers, narwhal-like tails and solid gray skin, he said.

Mads Peter Heide-Jørgensen, the narwhal scientist, convinced the hunter to donate it to the Natural History Museum of Denmark for analysis. But at the time, he could only conclude it was a possible hybrid or deformed beluga.

Thirty years later, he and others have finally cracked this cold case. A genomic analysis of DNA extracted from the John Doe skull revealed that it belonged to an adult, first generation son of a narwhal mother and beluga father. The study, published Thursday in Scientific Reports, shows how a little DNA can go a long way, that hybridization isn’t that unusual and that as long as museums keep storing mysterious stuff, the right technology might one day set their stories free.

“There are certainly things lying around that can tell us about the natural world around us and how it shifts and changes,” said Eline Lorenzen, the museum collection curator who first decided to pull the skull off its shelf.

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Her lab extracted DNA from the dust of its teeth and bones, and compared it to genomes derived from tissue samples of belugas and narwhals from the same area. The analysis, conducted by Mikkel Skovrind, a graduate student, revealed it was a male and a 50/50 narwhal and beluga mix. A first generation hybrid — perhaps a narluga?

And analysis of mitochondrial DNA, which only comes from the mother, indicated — surprise — she was narwhal. Generally only male narwhals have tusks, which may play a role in advertising social dominance and attracting females, kind of like deer antlers. But this female narwhal didn’t seem to mind a tuskless beluga.

The hybrid whale’s combined features are completely weird, Dr. Lorenzen said. “It’s like if you took 50-percent beluga and 50-percent narwhal and shoved their teeth in a blender, that’s what would come out.”

That probably complicated slurping prey like a toothless narwhal or chewing it like a beluga. Despite that, the large skull indicated he had survived well into adulthood. Remnants of carbon and nitrogen in his bones suggested that he had fed on the seafloor, more like a walrus or bearded seal than a typical monodontidae.

Reproduction may also have challenged the creature. Many hybrids in nature — think mules, the offspring of a horse and donkey — are sterile.

Others like him probably have existed, but wouldn’t occur frequently, said Randall Reeves, a marine mammal biologist who has studied the skull, but was not involved in the recent genomics research. There is no evidence in the beluga or narwhal genomes of interbreeding in at least a million years.

The skull came from one of the few places on Earth where narwhals and belugas are found together during mating season. And despite constant monitoring of these and other whale populations by experienced hunters, government agencies and biologists, there are no reports of other oddballs, not even rumors, Dr. Heide-Jørgensen says.

Still, the chances that this occurred only once in a million years and they just happened upon the skull are slim, said Dr. Lorenzen.

Blue whales have recently hybridized with fin whales. And belugas have interacted with and even adopted narwhals. Humans and Neanderthals, horses and donkeys, polar bears and brown bears, at least 16 different whales: Genetics are revealing that hybridization, though rare, may be more common than we think.

For now, it’s only possible to speculate about the circumstances that led to the conception of the baby beluga narwhal, perhaps the cutest-sounding animal that ever existed. But perhaps it’s just a matter of time before someone unlocks the secrets of other weird whale skulls that are waiting to be found.



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