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There is "overwhelming" evidence whales and dolphins live in "complex" societies with distinct cultural traits, scientists have found.
This is according to a landmark study of brain sizes and social behaviours in 90 different species of cetacean - a branch of aquatic mammals that includes dolphins, whales and porpoises.
Just like with primates, the cetaceans' sophisticated brains allow them to work together for mutual benefit, including teaching each other how to use tools and hunting cooperatively.
In a seemingly compassionate manner, they were also observed caring for the youngsters of the herd who weren't their own offspring, and showed an ability to work with different species, including humans.
They were even spotted using complex sounds to communicate vocally, and their ability to "speak" to each other was particularly fascinating for the scientists.
The researchers observed the creatures using different "dialects" and recognising different "names" or identifying "whistles" with each other.
Lead scientist Dr Susanne Shultz, an evolutionary biologist at the University of Manchester, said: "As humans, our ability to socially interact and cultivate relationships has allowed us to colonise almost every ecosystem and environment on the planet.
"We know whales and dolphins also have exceptionally large and anatomically sophisticated brains and therefore have created a similar marine-based culture.
The brain sizes and social behaviours of 90 different species of cetacean were observed.
"That means the apparent co-evolution of brains, social structure, and behavioural richness of marine mammals provides a unique and striking parallel to the large brains and hyper-sociality of humans and other primates on land.
"Unfortunately, they won't ever mimic our great metropolises and technologies because they didn't evolve opposable thumbs."
The study, published in Nature Ecology & Evolution, argues that anatomically sophisticated brains are an evolutionary response to social environments which are complex and information-rich.
Co-author Dr Michael Muthukrishna, from the London School of Economics, said: "This research isn't just about looking at the intelligence of whales and dolphins, it also has important anthropological ramifications as well.
"In order to move toward a more general theory of human behaviour, we need to understand what makes humans so different from other animals.
"And to do this, we need a control group. Compared to primates, cetaceans are a more 'alien' control group."
Dr Kieran Fox, another study participant and a neuroscientist from Stanford University, said the research showed how the non-primate brain structure of cetaceans still allowed sophisticated thinking.
"A new question emerges," said Dr Fox: "How can very diverse patterns of brain structure in very different species nonetheless give rise to highly similar cognitive and social behaviours?"
(SKY NEWS)
