A new study of 90 different species of whales and dolphins has found a striking similarity in the evolution of the brains of cetaceans and primates, including humans. The study looked at the social complexity of each species, and used that factor to determine if brain size could be used to predict the richness of the culture of each type of marine mammal.

Physically speaking, dolphins and whales have well endowed brains, with sperm whales and orcas taking the top number one and two spots in brain size, respectively, in the animal kingdom (including humans), and many species of cetaceans have a higher brain to body mass ratio than humans. Along with this, cetaceans also have complex social structures, typically within tightly-knit groups, that includes behavior such as cooperative hunting, shared language, including the ability to assign names to individuals, and the ability to cooperate with other species.

The study found that encephalization, or the expansion of the brain, appears to occur in response to the increased complexity of an individual species’ social structure. Intelligence itself does not appear to rely on brain size — many birds, especially ravens, are downright brilliant, despite having "bird brains" — however, according to the study "brain size predicts the breadth of social and cultural behaviors, as well as ecological factors."

"As humans, our ability to socially interact and cultivate relationships has allowed us to colonize almost every ecosystem and environment on the planet," according to study co-author and evolutionary biologist Dr Susanne Shultz, with the University of Manchester’s School of Earth and Environmental Sciences.

"We know whales and dolphins also have exceptionally large and anatomically sophisticated brains and, therefore, have created a similar marine based culture," Schultz continues. "That means the apparent co-evolution of brains, social structure, and behavioral richness of marine mammals provides a unique and striking parallel to the large brains and hyper-sociality of humans and other primates on land."

Stanford University neuroscientist Dr. Kieran Fox, also involved with the study, points out that "cetaceans have many complex social behaviors that are similar to humans and other primates. They, however, have different brain structures from us, leading some researchers to argue that whales and dolphins could not achieve higher cognitive and social skills.

"I think our research shows that this is clearly not the case. Instead, a new question emerges: How can very diverse patterns of brain structure in very different species nonetheless give rise to highly similar cognitive and social behaviors?"