Cultural Differences May Be Splitting Orcas Into Different Species

Brilliance | Dec. 18, 2017

Orcas and humans share a lot of similarities. We're both intelligent, we have the same average lifespan, and we're both social creatures. In fact, our social lives are so similar that they're causing another similarity: cultural differences may be causing orcas to evolve into different species.

How It's Happening

Like people, orcas live all over the world. The ocean-dwellers have no natural boundaries, so they're free to move about. And move they do, up to 100 miles (160 kilometers) a day. This freedom also means that they can mate with any other orca they encounter, even if it was born on the other side of the world.

But scientists noticed that in practice, this isn't the case. Many orca populations have an area they call home, where they hunt particular prey using particular strategies known only to them. For example, orcas in the Antarctic will charge an ice floe in formation to knock seals into the water and devour them. Orcas off the Norwegian coast, meanwhile, work together to herd schools of herring into a tight "bait ball," which they slap with their tails to stun the fish and make them an easy dinner. Orcas also seem to have different dialects. Just like American families use different techniques in the kitchen than Japanese families, these are cultural differences that make orca groups distinct from one another. This is no metaphor: biologists actually refer to these behaviors as culture.

Sometimes, cultural differences translate into genetic differences. For example, dairy farming made some humans evolve the genes for digesting milk. Andrew Foote at the University of Bern, Switzerland and his team set out to determine whether this happened in orcas. It did, in fact: the five groups the researchers studied each had distinct genomes to mirror their cultural niches. They're still the same species, of course, but if this keeps up, they won't be for long.

Why It's Important

This makes orcas the first non-humans whose evolution has been caused by culture. It means that culture could be a driving factor for changes in a number of species, though they would probably require the same kind of intelligence and social strengths that humans and orcas share. It turns out that in both animals, culture is a more important part of life than we ever gave it credit for.

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