Convergent evolution with humans
WHALES and dolphins (order Cetacea) have very big brains, live in closeknit social groups, have elaborate relationships, and talk to each other as humans do.
Humans and other primates are only distantly related to cetaceans, but both groups of mammals have developed unusually large brains. Evolution of extremely large and complex brains (encephalisation) is not uniform among mammals, but occurred in both groups because each independently developed advanced sociality. This involved the coevolution of intelligence, sociality and language. Social learning is essential in both humans and cetaceans.
Cetaceans are marine mammals very closely related to the order Artiodactyla (eventoed ungulates that include sheep, cattle, pigs and hippopotami, having two or four hoofed toes). Cetaceans evolved about 50 million years ago, their closest living ancestor being a hippopotamus.
Humans are primates (an order of mammals that dates back 65 million years). The first primates were furry squirrellike in size and shape, and had grasping hands and feet for manipulating objects and climbing trees. Stereoscopic vision developed early. Monkeys evolved around 33 million years ago.
It seems remarkable that these two very dissimilar groups of mammals should have each developed such similar patterns of complex social behaviour and accompanying large brains, language and intelligence.
A major study published last month in Nature Ecology & Evolution associating the complexity of cetacean culture and behaviour with the size of the brain was conducted jointly by research teams at the universities of Manchester (UK), British Columbia (Canada), the London School of Economics (UK) and Stanford University (United States). It found that 90 species of cetaceans (whales, dolphins and porpoises) all had rich cultures and societies resembling those of humans. The similarities include: complex social alliances, teaching others how to hunt and use tools, teamworking when hunting, talking and complex vocalisation with regional dialects, individually distinctive methods of vocalising and ‘‘name’’ recognition, teamworking with humans and other species, foster parenting, and social play.
One of the researchers, Dr Susanne Schultz, said the similarities between humans and cetaceans result from the cetaceans’ exceptionally sophisticated brains, allowing cetaceans to create a similar culture in the oceans.
She noted that they will never produce a submarine counterpart of our great metropolises and technologies because cetaceans did not evolve an opposable thumb.
This large work provides a fresh insight into the human condition through studying a very alien species that has evolved a comparable social culture, highlighting the need to treat other species with respect and empathy, as fellow inhabitants of our fragile and precious planet.
(Fox, K.C.R., Muthukrishna, M, Schultz, S 2017. The social and cultural roots of whale and dolphin brains. Nature Ecology & Evolution DOI: 10.1038/s415590170336y)