Narwhals have survived 1 million years despite low genetic diversity: study

The narwhal has survived as a species for one million years, despite having low genetic diversity — a discovery that has scientists scratching their heads.

Eline Lorenzen, an associate professor and curator of mammals at the Natural History Museum of Denmark at the University of Copenhagen, is a co-author in a recent study that lays out the findings.

She says the narwhal’s resiliency over its evolutionary history is surprising because that’s not something generally seen in species with low genomic diversity.

“If you think of it as a toolbox that you have at home where you have lots of different tools in case something happens at your home … the more tools you have available in your toolbox, the higher chances you’ll have the correct tools to fix whatever’s going on,” Lorenzen said. 

Eline Lorenzen says the mystery isn’t why narwhals have low genomic diversity but how they’ve survived over a million years. (University of Cophenhagen)

“Now the narwhal, it looks as if it has a toolbox with just not very many tools, yet it’s been able to fix whatever it has needed to fix throughout its evolutionary history.”

Generally, Lorenzen said, a species will only display low genetic diversity after an event causes a population to crash, or a subset of a species establishes itself in a new area.

She said scientists understand why narwhals have low genetic diversity — they have a very low population of approximately 170,000 across Arctic waters. The mystery is how they’ve been able to survive for so long.

“We hypothesized that the species, because it’s had such low diversity for so long, has somehow adapted to surviving with that low diversity.” 

But Joanasie Mucpa, an elder who lives in Pond Inlet, Nunavut, where the world’s largest population of narwhal migrates every summer, has another theory. He suggested the narwhal may have adapted over its evolutionary history through migration.

“The animals follow their food all the time,” he explained.

Lorenzen said her team didn’t speak to local Inuit populations for this particular study.

Unexpected discovery

The genome discovery itself came as a bit of a surprise to Lorenzen’s research team. They were sequencing the genome of the narwhal and comparing it with DNA from ancient narwhal specimens “to see what is a narwhal and what is not,” she said.

“Then we got this super interesting finding of it having a really unique evolutionary trajectory.”

The question now is, with such a low genomic diversity, how well will narwhals be able to adapt to a changing Arctic climate?

Lorenzen explained a species will either go extinct, move to a new location or adapt to a changing environment. With the narwhal, she doesn’t know what to expect.

“Our concern is that, because of the low variation across the genome, the narwhal does not have a lot of opportunity to adapt,” she said.

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