Research has revealed that orcas are the first non-human species whose evolutionary adaptations are altered by culture. According to a team of scientists based out of the University of Bern, Switzerland, different populations of killer whales have shown rapid genomic changes in response to different whale behaviors related to geographical distribution or hunting patterns:
Functional enrichment analyses provided evidence for regional genomic divergence associated with habitat, dietary preferences and post-zygotic reproductive isolation.
The researchers behind this study examined the habits and genomes of five different groups of orcas - three in the Antarctic ocean and two in the Pacific ocean. Some of the groups were observed to hunt by corralling fish into balls, while other groups hunted by stranding themselves onto land where mammals such as seals could be caught.
Not only did each separate group of whales display vastly different behavior, but also had distinctly different genomic traits. While all killer whales share common ancestors around 200,000 years ago, today there are genetic differences among populations that imply separate evolutionary lineages.
These genetic differences are believed to be due to differences in geographic distribution or hunting and mating behaviors among separate groups of orcas. For example, among orcas living in colder waters, the genetic markers for the growth of adipose tissue (fat) was much more prominent in response to selection based on environmental stimuli.
Furthermore, different levels of amino acids involved in the breakdown of animal-based proteins were observed among the different groups of orcas, implying that geography-specific diets have influenced the evolution of orcas’ digestive physiology.
According to the research, this implies rapid changes that occurred after a past evolutionary bottleneck:
Behavioural adaptation has facilitated the colonization of novel habitats and ecological niches. Founder effects and rapid formation of reproductive isolation, followed by population expansion, have promoted genome-wide shifts in the frequency of alternative alleles in different ecotypes due to genetic drift.
In this way, orca evolutionary history mirrors that of modern humans. When humans developed agriculture and began keeping livestock, human consumption of milk rose. In response, the genes for lactose intolerance became more prominent in many human populations. The shift to agriculture also triggered selections for physiological changes in response to the culturally-driven changes in human diet, such as smaller teeth and brains.
This new research sheds light on the complex mechanisms behind evolutionary adaptations. As human culture continues to evolve at an ever-increasing rate due to the changes brought about by the information age, we might begin to see unprecedented and unexpected changes to the human genome.