Orcas are the first non-human species to have demonstrable coevolution of genes and culture. What does that mean? The most famous example of human culture influencing genetic evolution is lactose tolerance: humans gained genes that help digest cow milk only after turning to dairy farming. And there are many other examples, not all of which carry benefits today-- sickle cell anemia in yam farmers, and type II diabetes in seafaring cultures, for example. Both evolved due to fitness pressures brought about by culture: increased incidence of malaria for people chopping down trees to make yam farms, and risk of hypothermia and starvation on long sea voyages for the latter. Now, researchers have strong genetic evidence that orca evolution has similarly been driven by culture. But what are we talking about when we refer to "culture" in animals? Surely orcas are not farming yams or, uh, building boats...
Anytime animals have distinct behaviors that are transmitted through learning or imitation, scientists define this as culture. For example, orcas speak in distinct dialects, and even have peculiar "memes" or cultural fads! When a female orca started carrying around a dead salmon in her mouth, this swiftly became a hot fashion fad that spread like wildfire for a summer. Just as quickly as it arose, like a Furby or bellbottoms, the dead-salmon-carrying-fad disappeared (I term it the "mullet analogue in cetaceans").
But orca culture is most famously illustrated by their wide variety of intergenerational hunting strategies, which cluster in discrete cultural groups. The Stranding Orcas of Patagonia* launch their bodies onto land, effectively "stranding" themselves in an attempt to kill elephant seal pups (video of similar behavior here. Warning: orcas play with their still-living prey, so don't watch unless you want to see that). Carousel Feeding Orcas take turns looping in circles beneath their piscine prey, chattering and blowing bubbles to weave the fish tightly together at the surface (in a nightmarish orca carousel). The famous Wave Generatorscoordinate their swim-surges towards an ice floe, sending giant waves crashing under and over the floe (and sending their prey careening into the water). These are just three examples; orca pods all over the world have a wide variety of advanced, specific hunting strategies. Because they are long lived and social, young orcas have plenty of time and ability to learn these culturally transmitted behaviors.
Amazingly, scientists have now documented genetic changes co-evolving with these cultures. Writing in Nature Communications, Andrew Foote and colleagues find that although orcas radiated less than 250,000 years ago, "socially inherited ecological niches" have promoted rapid allele diversification between different cultural groups. In other words, culture sparked rapid evolution!
We have now documented coevolution of genetics and culture in two species on earth: orcas, and humans. Which will be next?
* Which would be an epic band name
“One of the main conclusions is that variation within killer whales, humans and likely many other species arises from multiple interacting processes rather than being attributed to just culture, ecology or genetics,” says Foote. But Whitehead is not sure that the co-evolution of genomes and culture will turn out to be a common feature throughout the animal kingdom. After all, killer whales and humans share a number of unusual features, including their intelligence, longevity and social natures – which work together to create an ideal environment for social learning that can strengthen group identity and reinforce genetic distinction. “In both,” says Whitehead, “culture is in the driving seat.”