Around 700 million years ago, we find the first ever sensorimotor systems laying down the first ever memories in the first ever minds. The memories belong to marine invertebrates on the ocean floor. What they remember is the chemical ambience of the water where they were a few seconds ago. They compare this memory with where they are now, before deciding whether to swim straight ahead or to do a tumble-turn. They navigate by chemical concentration gradients, seeking or avoiding chemicals, in a type of movement called chemotaxis.
In ‘Animal Evolution and the Origins of Experience’, Peter Godfrey-Smith goes back to the Cambrian Explosion fossil record to show how ‘mind evolved in response to other minds’, and ‘bodies evolved in response to other minds’.
For most of the Ediacaran Epoch (635–541 million years ago) nervous systems don’t put in much of a shift. After a light spot of metabolic homeostasis, the mycoplasma unwind with a lazy backstroke. Even at this stage, however, these multicellular organisms establish a rule that will hold will hold for the rest of time: right from the start there is no brain without brawn. As Peter Godfrey-Smith says ‘only organisms with neurons also have muscle cells’.*
* Peter Godfrey-Smith, ‘Mind, Matter and Metabolism’, Journal of Philosophy, 2017.
The Ediacaran Eden is the peaceful flotation tank of evolution. Life on earth will never again be so Zen. It’s a steam bath, a jacuzzi. Ediacaran marine invertebrates are benthic grazers on microbes, filter feeding on whatever comes their way. Nobody eats anybody else. There’s no predator–prey action. No fossils of half-eaten organisms come from the Ediacaran.
But all that changes with the Cambrian Explosion, which inaugurates both the Cambrian Period (541–485 million years ago) and the three-hundred-million year long Paleozoic Era. The Cambrian Explosion does for the Ediacaran what Prohibition does for Chicago. Now, the wild rumpus begins, and there goes the neighbourhood! Signs of predation are everywhere. The Cambrian fossil record shows a body-count going up and up. Everyone is packing some kind of piece: a claw, a spike, armour, pincers and shivs. With predators lurking in the murky depths, you need to react in real time to what is going on around you.
‘New kinds of bodies appear’, says Peter Godfrey-Smith. ‘For the first time in history the details of what were going on around start to matter.’ Now the first antennae go up. Now come the first getaway fins and spines. Now come the first real-time sensory-motor complex arcs. Now come what Peter Godfrey-Smith characterises as ‘image-forming eyes for tracking other animals at a distance’.
To survive the Cambrian you need a body capable of anticipating or responding to whatever dark and devious proto-thoughts are going on in the Haikouichthys swimming towards you. This is what he means by saying that both mind and body evolve in response to other minds.
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In The Sea Around Us (1951) Rachel Carson, the famous ecologist and marine biologist, describes how the composition of our blood faithfully records the precise ratios of sodium, potassium and calcium in Cambrian oceans. Since the brain works by means of pumping sodium and potassium ions, it is tempting to speculate that the ability of the mind to bring just one thing at a time into consciousness copies chemical patterns used in taming the pre-Cambrian benthic blitz. In ‘Mind, Matter and Metabolism’ Peter Godfrey-Smith describes how life originated in a ‘molecular storm’:
[T]he origin of life went not from simple to complex but from disorderly to orderly … The evolution of life was a matter of channeling and taming a sea of interactions not taking a few simple interactions and stringing them together.
Perhaps organisms mimicked or accidentally ingested the ambient chemical processes. Inside the cellular membrane this biochemistry – as if conscripted – carried on doing what it had been doing before, but this time it found itself taming not an ocean but incoming sensory overload into one coherent and orderly mental workbench.
From a blizzard of mental activity the mind brings just one or two things into consciousness, and lays them on the mental workbench or ‘global workspace’. Within this noisy chemical bombardment the brain finds its scallop-shell of quiet. We say ‘I can’t think’ when there is too much going on in our heads, not when there’s too little. The exception to this rule is Homer Simpson’s sad lament: ‘I want to be left alone with my thought’. Is it possible that flow patterns in the brain mimic biochemical patterns from ancestral seas?
This is not a hypothesis that Peter Godfrey-Smith himself entertains, I hasten to add. In fact, in ‘Cephalopods and the Evolution of the Mind’,* he suggests a more convincing hypothesis than mine for how the mental workbench evolved. It may have come about he suggests by the demands of extractive foraging, and by ‘the way the need to perform novel combinations of operations presses events into consciousness … [because] they must maintain information for explicit use over a period of time.’ In his ‘Cephalopods’ paper, Peter Godfrey-Smith is intrigued by the way that octopuses achieve a single integrated consciousness despite the fact that two-thirds of their neurons are in their arms:
* Peter Godfrey-Smith, ‘Cephalopods and the Evolution of the Mind’ Pacific Conservation Biology, 2013.
Although many processes are going on in parallel in our brains, what we are aware of at any time in a single integrated scene … The familiarity of the fact that conscious experience is integrated in this way disguises the fact that this integration is a significant achievement for our brains.
If it is a significant achievement for us, then how much more so for the decentralised octopus! The last common ancestor of human and octopus shimmied along the Ediacaran ocean floor, about 600 million years ago. Since they have a completely different evolutionary trajectory to us, this makes them, he says
an independent experiment in the evolution of large and complex nervous systems … Where their minds differ from ours, they show us another way of being a sentient organism.
Because octopuses live short lives, only a few years at best, neoteny has nothing to do with the evolution of their smarts as it has for ours. And since octopuses are not very sociable, you can’t ascribe their intelligence to the social brain theory, which is another theory for the origin of human intelligence. And yet the octopus demonstrates sophisticated levels of planning and tool use in excess of even the higher primates.
About twenty years ago, for example, marine biologists in the Indonesian Sea first noticed octopuses carrying pairs of coconut shells, like stacking bowls. No-one knew where they were taking them or what they were going to do with them when they got there. It remained a mystery for a couple of decades, but a recent paper appears to have solved the enigma. The octopuses, it turns out, are using the coconut shells as a portable storm shelter. When cyclones roll rocks and stones along the ocean floor, the octopuses climb into the coconut halves, and seal them shut with their strong arms. It’s a self-assembly spherical storm refuge.
I can’t tell you how depressed I was by this finding. For as long as I live, a part of me will always hope that the real reason octopuses carry pairs of coconut shells is for the sarcastic ridicule of seahorses.