Dolphins: look like fish, think like primates?

Although they live in water and they may look more like a big fish, dolphins are actually more similar to primates (which includes us humans) than you might think. In particular the size and complexity of the dolphin brain, which relates to their cognitive capacity, has been found to compare on a primate level, especially with the human brain. The dolphin brain is bigger in size than the human brain, and when measured as a proportion of body size many cetacean (whales, dolphins and porpoises) species follow closely behind humans, and in fact ahead of our closest relatives, great apes. This suggests that although still falling behind humans, dolphins may have a higher capacity for cognition, or intelligence, than other non-human primates and our closest land mammal relatives.

There are many similarities and differences between human and dolphin brains, primarily to do with the brain structure and in relation to function. For example, the dolphin brain has a completely different organisation compared to the primate brain, but they have been observed to exhibit and execute the same level of behavioural and cognitive abilities. Research shows that dolphins are capable of solving problems, communicating and processing in ways that are as complex as primates. Through MRI scans it has been found that the dolphin brain is is composed of structures seen in the human brain, but organised differently, and therefore it is possible that dolphins may be capable of higher cognitive capacities similar to humans. Through evolution the human brain grew frontally, whereas the dolphin brain has grown in width. The high volume of convolution, or brain folding, present on the dolphin brain and also seen to a very similar degree on the human brain, increases the surface area of the brain and results in higher neural density and complexity, which increases the potential of enhanced cognition.

When it comes to determining cognition, or 'intelligence', although brain size and structure is taken into consideration, many scientists believe that certain behaviours and abilities exhibited also play a major role in the level of intelligence of an animal – these behaviours and abilities are known as 'intelligence indicators'. These 'indicators' include self awareness, tool use and communication, and show that the animal is able to learn and develop beyond their innate behaviours. As well as their complex brain structure, there is evidence of dolphins demonstrating these 'indicators' both in captivity and wild. This has lead us to question just how intelligent these animals are, and whether such animals should be treated as non human 'persons', having the right to freedom of living in their natural environment and not being kept in captivity for public entertainment!