Killer Whales Orcas

Culture drives distinct genetic evolution in killer whales — the first non-human animal to do so

Researchers at University of Bern, Switzerland, found that Orcinus orca (killer whales) populations have evolved distinct genetic lineages due to unique hunting strategies. Adults pass down knowledge about what and how to hunt to the young, a form of cultural transfer. This implies that culture has had such a profound effect on the orcas that individual groups have started to diverge. This has only been observed in humans before.

Killer Whales Orcas

Credit: Pixabay

Humans are a globally dispersed species, but the populations vary in their genetic makeup. Environmental cues like temperature, food availability, the seasons and such force adaptations like dark skin in Africa, for instance. But besides the natural ecosystem, humans also receive inputs from their own fabricated microcosmos. We wear clothes, live in homes that shelter us from the elements and farm food.

These cultural cues will also trigger genetic changes, which will vary from population to population. Perhaps the clearest example is the domestication of cattle which forced the adaptation of lactose tolerance genes. Lactose tolerance varies greatly by geographical distribution, though. Up to 90 percent of Northern European populations are lactose tolerant, but in some Asian countries, 90 percent of the population is lactose intolerant.

Lactose Tolerance map

Credit; Nature

Like humans, orcas are also highly dispersed around the globe, living in waters ranging from the tropics to the poles. Like humans, orcas form communities which occupy a certain single area for a very long time, like a permanent settlement. In these communities, the orcas will develop their own hunting strategies, adapting to the kind of prey available. Some will target fish, while other groups or pods will specialize on seals.

These very niched strategies are sophisticated and require the kind of coordination and knowledge which isn’t available from birth. Instead, the adults will train the juveniles over decades if necessary.

Knowing this, some biologists wondered: will these distinct cultural trends result in distinct genetic populations in orcas just like in humans? Andrew Foote at the University of Bern and colleagues set out to answer this question. The team sampled and sequenced genetic material from 50 killer whales belonging to five distinct niches.

Results suggest the five cultural niches corresponded to exactly five distinct genomes, confirming the hypothesis. All of these groups share a common ancestor which lived as recently as 200,000 years ago, the researchers wrote in Nature Communications. 

Foote says each niche was occupied initially by a small group of founding members then gradually expanded. These founding members, which we can call eccentrics because they decided to venture into a new niche, were successful thanks to their individual flexibility. But the survival of the entire pod over centuries in the same niche relies on know-how transfer, hence culture.

This research is striking because it proves culture is powerful enough to transform the genetic makeup of populations, in humans and non-human animals alike. Is this the case of other animals besides humans and orcas? Should be, but there aren’t that many that can boast the necessary characteristics like sophisticated social structure, longevity and high-order intelligence. Whales and other primates might also confirm the findings.

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