Cultural experiences shape orca whale evolution

While researchers have come to accept that cultural experiences have played a key role in human evolution, they had never discovered evidence to suggest that any other species of living creature underwent biological changes in order to fulfill a specific niche – until now.

Writing in Tuesday’s edition of the journal Nature Communications, Andrew Foote, an ecologist at the University of Bern, Switzerland, and his colleagues revealed that they had found evidence indicating that such cultural experiences might shape killer whale evolution.

As New Scientist explained, humans developed genes for lactose tolerance after they first became dairy farmers, indicating that their behavior had a direct influence on their genomes. Now, Foote and his fellow researchers have found that, despite their wide distribution, individual orca groups appear to remain in one general area and stick to a specific predatory strategy.

For instance, some heard their prey into bait balls, while others intentionally beach themselves in order to attract seals or other mammals. Since these groups tend to remain stable for up to several decades, these behaviors can be passed on from one generation to another. The authors identified five specific niches, and set out to see if the groups were genetically distinct from one another.

They found that the genomes of killer whales could be categorized into five distinct groups, each of which directly corresponded with one of the five cultural niches. Even though each of the orca groups shared a common ancestor as recently as 200,000 years ago, the research revealed that all of them experienced a different genetic evolution due to this social learning.

Orca whale stalking a seal

Cultural experiences change how certain groups of orca whales hunt. Credit: John Durban, NOAA Southwest Fisheries Science Center

Geographic spread is the key to orca evolution, authors says

While each group is a member of the species Orcinus orca, all of them exhibit a significantly different set of behaviors, according to the Guardian. Some live on fish while others prefer to dine on mammals and still others consume birds and reptiles. Some live in the Arctic and some in the Antarctic, and some tend to travel while others tend to roam around.

In all cases, Foote explained, these cultural niches have had an impact on the genes of the killer whales, and as he told the British newspaper, “What is remarkable is that it is incredibly close to what we see in humans. Generation time – the time of becoming an adult and having offspring – is also quite similar, roughly 25 years, and they live to roughly the same age.”

His team’s findings help to explain how orcas became genetically diverse from one another, New Scientist said. Each of the five groups were formed by a small offshoot of the overall killer whale population, and as it expanded over time, this so-called “population bottleneck” resulted in these groups adapting and evolving differently in response to their surroundings, thus ensuring that all of the groups ultimately developed a unique and distinctive genetic identity.

“I think it is linked to the geographic spread,” Dr. Foote told the Guardian. “Kkiller whales are found from the Arctic to the Antarctic and all the waters in between. Humans and also brown rats are the only other mammals that spread across such a wide geographic range. I think it is all the different prey items that make it possible. As a species they feed on almost everything.”

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Image credit: Thinkstock

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