Cetaceans, the group of animals including dolphins and whales, are intelligent, big-brained creatures with several social behaviors similar to those of humans. And, according to new research, the bigger the brain, the more social the cetacean.
Dolphins engage in several behaviors that demonstrate their sociality and resemble human culture. They play, babysit one another’s offspring, hunt cooperatively and teach one another how to do things. “They have signature whistles. They actually have names for each other,” study co-author Michael Muthukrishna tells Newsweek. Muthukrishna is an assistant professor of economic psychology at the London School of Economics.
Many scientists have sought evidence of connections between dolphin behavior and the dolphin brain. Some of them have approached the topic by calculating the encephalization quotient—the ratio of actual to predicted brain mass for a given species relative to body mass. But that measurement is limited in its usefulness. “You do need to control for body size in some way,” says Muthukrishna. “But a lot of research is actually showing that encephalization quotient is actually a terrible measure of brain power.”
This new study, conducted by researchers at the University of Manchester, the University of British Columbia, the London School of Economics and Political Science, and Stanford University, took a different tack. Instead of looking at the encephalization quotient, they focused on absolute brain size. Their research, published today in the journal Nature Ecology and Evolution, found a relationship between social behaviors and absolute brain size.
Researchers gathered data from years of studies examining brain sizes of 90 different species of whales and dolphins and cataloging their social intelligence. Then, they gathered data from studies done by field scientists documenting the social behaviors of wild dolphins and whales in the ocean. By assigning a value to the different species based on how often they took part in social behaviors, they were able to plot the sociability and brain size on a graph. The graph showed that, as brain size increased, so did social behaviors.
Scientists have long wondered whether our distinctiveness as a species is evident in our brain size. Research on brain size and sociality within humans and other primates have faced a challenge establishing a causal relationship between intelligence and sociality because nonhuman apes are closely related to humans. They don’t represent a good species to use as a control against humans because they are too similar to us genetically.
Dolphins may accomplish what primates cannot. “It would be nice if we could discover an alien species out there and to measure us against, to discover what makes us different, but we don’t have that,” Muthukrishna says. “But we do have this sort of alien taxa [evolutionary group] under the water.” That’s why cetaceans are ideal.
And the findings point strongly to the notion that social structures grow in proportion to brain size in humans too. "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,” said study co-author Susanne Shultz, an evolutionary biologist in Manchester's School of Earth and Environmental Sciences, in a statement.
Although whales and dolphins do have humanlike societies in a social sense, they also lack certain abilities that were necessary for human evolution. They can communicate well and hunt efficiently, but they do not have thumbs required to make complex tools, and they can't use their environment to advance in the way humans did. “They will never discover fire because it’s very difficult to light a fire underwater,” says Muthukrishna.
Instead, the sophisticated aquatic mammals will have to settle for being overlords of the ocean.
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