I was reading about whales and wondered why did only narwhals, among all other species of whales, evolve to have tusks? Is there a specific environmental reason, for example something unique about the Arctic environment that requires them to have a tusk for easier survival?

I researched a bit and found many reasons why narwhals have tusks, but couldn’t find a reason why other whales do not have tusks.

I was reading about whales and wondered why did only narwhals, among all other species of whales, evolve to have tusks? Is there a specific environmental reason, for example something unique about the Arctic environment that requires them to have a tusk for easier survival?

I researched a bit and found many reasons why narwhals have tusks (e.g. weapons for fighting other male narwhals to compete for mates, sensing the environment, attracting female narwhals, echolocation, stunning prey for easier hunting) but couldn’t find a reason why other whales do not have tusks.

Sources: https://www.google.com/amp/s/api.nationalgeographic.com/distribution/public/amp/news/2017/05/drone-footage-narwhal-tusk-mystery

https://www.google.com/amp/s/ocean.si.edu/ocean-life/marine-mammals/why-tusk-real-life-unicorns-sea-and-tusks-make-them-famous%3famp=

https://oceanconservancy.org/blog/2019/03/08/exactly-narwhal-tusk/

https://scholarblogs.emory.edu/evolutionshorts/2014/04/25/the-evolutionary-significance-of-the-narwhals-tusk/