In his book  Other Minds – the octopus and the evolution of intelligent life  Peter Godfrey-Smith  goes back 600 million years to find the common ancestor of octopuses and humans. It was probably a simple worm-like creature, living at a time when no organisms had made it on to land.

Octopus cyanea at Lizard Island in an unusual inflated posture. Note the dark false eyespot below the real eye and regular rows of white spots near the arm tips. © Vanessa Messmer


Octopuses,squid and cuttlefish are all cephalopods, a class of molluscs.  It also includes nautilus, which have distinctive external shells. Cephalopods are found all around the Australian coast, including on the Reef. PGS writes “Because our most recent common ancestor was so simple and so far back, cephalopods are an independent experiment in the evolution of large brains and complex behaviour.  …evolution built minds twice over.  This is probably the closest we will come to meeting an intelligent alien”.

This photograph, taken at Whyalla, shows the great range of colours giant cuttlefish produce using mechanisms layered in their skins. © Peter Godfrey-Smith


The giant cuttlefish and octopuses that feature in Other Minds are remarkable animals. Octopuses have three hearts that pump blue-green blood, using copper as the oxygen-carrying molecule (our red blood uses iron).  They are able to sense light and colour with their skin as well as with their highly developed but colour-blind eyes. They can recognise individual human faces and are clearly quite smart.  They are able to morph their colours and shapes across a bewildering range of possibilities, making it very difficult to know if the animal you saw a few moments ago is the one you are seeing now.  Some are masters of camouflage and impersonation.

This is a photograph of an octopus:

© Peter Dudley-Smith

Here it is again, with labels

Note how the head has adopted a dark colour and shape to blend in with the rock and crevice, while the arm has adopted a colour and texture that blends with the sand. © Peter Godfrey-Smith


This octopus has produced a very close colour match to the seaweed behind it. © Peter Godfrey-Smith


Mimic Octopus Thaumoctopus mimicus at Lizard Island © Darren Coker.  This animal is able to change its colours and shape at will.  It goes beyond camouflage to mimic and impersonate poisonous animal species, including lion fish, sea snakes, flatfish and jellyfish, as a way of discouraging its predators.


The same Mimic Octopus in a different shape © Darren Coker July 2012.  Darren followed it for an hour as it demonstrated impersonation skills, at one stage swimming like a flounder.


Octopuses are able to get from A to B by jet propulsion which they achieve by squirting water through an organ called a ’siphon’. Compared with us, their central brains and distributed nervous systems are more integrated, less separate.  This is called “embodied cognition”.

This cuttlefish was called Kandinsky, after the Russian painter and art theorist who inspired the Expressionists. It displayed red-orange-green shapes flowing over its skin, like passing clouds. © Peter Godfrey-Smith


Octopus and cuttlefish are just two examples.  There are the countless other species of life in the sea, each wondrous in its own way. They are especially concentrated on coral reefs.

Other Minds provides a superb illustration of why marine science is important and worth supporting. The final sub-chapter begins with this observation: “The mind evolved from the sea. Water made it possible. All the early stages took place in water; the origin of life, the birth of animals, the evolution of nervous systems and brains, and the appearance of the complex bodies that make brains worth having.”  It concludes: “When you dive into the sea, you are diving into the origin of us all”.

A giant cuttlefish producing a complex range of reds, oranges and silver-white marks. It is also exhibiting a flow of temporary shapes in the skin above its eye. © Peter Godfrey-Smith