Other Minds: The Octopus, The Sea, and the Deep Origins of Consciousness, Peter Godfrey-Smith, c. 2016.

Other Minds: The Octopus, The Sea, and the Deep Origins of Consciousness, Peter Godfrey-Smith, c. 2016.

Opens with a quote from Williams James, The Principles of Psychology, 1890. 

The demand for continuity has, over large tracts of science, proved itself to possess true prophetic power. 

We ought therefore ourselves sincerely to try every possible mode of conceiving the dawn of consciousness so that it may not appear equivalent to the irruption into the universe of a new nature, non-existent until then. 

Octopuses, squids, and cuttlefish. Cuttlefish and squid close related to each other than to octopusses.  Modern soft-bodied cephalopods split into two main superorders

• Superorder Decabrachia (Decapodiformes) — 
• Ten-limbed group:
• Defining traits: Eight arms plus two specialized, retractable tentacles used for catching prey. They usually possess an internal stiffening structure (a chitinous pen/gladius or a calcified cuttlebone).
• Key Orders:
• Sepiida: Cuttlefish (characterized by a broad internal cuttlebone and W-shaped pupils).
• Teuthida / Myopsida & Oegopsida: Squids (pelagic and inshore squids with a flexible internal pen).
• Superorder Octobrachia (Octopodiformes) — 
• Eight-limbed group:
• Defining traits: Generally possess eight arms and lack the two long prey-capturing tentacles found in squids. Their internal shells are heavily reduced or completely lost (sometimes replaced by tiny stylets).
• Key Orders:
• Octopoda: True octopuses, split into Cirrina (finned, deep-sea varieties) and Incirrina (benthic/common octopuses and argonauts).
• Vampyromorphida: The vampire squid (Vampyroteuthis infernalis), which is not a true squid but an ancient relict group representing a sister lineage to octopuses.
• Early Divergence: 
• The lineage leading to Coleoidea lost or internalized its heavy external shell during the Paleozoic era (around 400 to 275 million years ago) to gain speed and agility against jawed fish.
• Modern Radiation: Following the K-Pg extinction event (which wiped out ammonites and belemnites), modern families of squids, cuttlefish, and octopuses rapidly diversified into the dominant forms seen today.
• The Decapod/Octopod Split: Genetic and fossil evidence shows that the ten-armed and eight-armed lineages split more than 300 million years ago. 

I find it simply amazing how "evolution" can do such amazing things. It is clear that the same genes are present (they don't disappear) but regulatory genes determine which genes will be expressed.

AI:

Connecting that to our timeline, the evolutionary event you are describing is endocochleation—the process where the shell becomes entirely enclosed by the mantle. When the ancestors of modern octopuses (the soft-bodied coleoids) internalized their heavy external shells roughly 300 million years ago, it triggered a massive cascade in gene expression.

Shedding that protective armor forced a biological tradeoff, shifting survival strategies from passive defense to extreme agility and intelligence. This morphological shift aligns with fascinating genetic mechanisms. 

Rather than inventing entirely new genes to dissolve the shell, coleoid ancestors underwent widespread genomic rearrangements. [I think Darwin and Darwinists would frown on the way this is described ... inventing entirely new genes....]

• Regulatory Changes: The gene regulatory networks controlling shell matrix proteins were modified or deactivated in specific tissues.Tissue Expression: The shell gland—which dictates shell growth in other mollusks—altered its expression patterns. Instead of secreting a heavy exterior wall, it minimized production, leaving modern octopuses with only tiny internal cartilage-like rods called stylets.

Unlocking the "Brain" Genes

• Without a heavy shell to drag them down, the metabolic energy of these creatures shifted toward spatial awareness, camouflage, and predatory hunting.
• Gene Expansion: This freedom correlates with a massive expansion in protocadherin gene families, which regulate complex neural connections.Dynamic Phenotypes: Octopuses heavily express these genes across their body, effectively decentralizing their nervous system so their arms can "think" and react independently.

Dynamic RNA Editing

• Because their physical defense was gone, octopuses evolved an extraordinary method of dynamic expression called high-level RNA editing. 
• While their foundational DNA remains fixed, they use enzymes to heavily edit the temporary RNA copies before they are translated into proteins. This acts as a real-time regulatory system, allowing them to rapidly alter protein behavior to survive extreme temperature swings and changing environments without waiting generations for DNA mutations.

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Cephalopods -- p. 4-5

Cephalopods: osctopuses, cuttlefish, squid.

Other well-known cephalopods: nautiluses, deep-sea Pacific shellfish which live quite differently from octopuses and their cousins. Octopuses, cuttlefish, and squid have something else in common: their large and complex nervous systems.

600 mya: LCA.

LCA: between humans and an octopus, of mammals and cephaopods. 600 mya, LCA.

600 mya, LCA. Almost twice as long as the LCA between mammals and birds.

Worms on the bottom of the seabed.

One path forward from that underwater split to our branch of the tree. It leads to vertebrates.

The other pad leads to a great range of invertebrate species, including crabs and bees and their relatives, and many kinds of worms, and also the mollusks, the group that includes clams, oysters, and snails. This branch does not contain all the animals commonly known as "invertebrates," but it doesinclude most of the familiar ones: spiders, centipedes, scallops, moths. -- p. 9.

Octopuses: the closes we may ever come to meeting an intelligent alien.

William James' epigraph: p. 11.

The key word in this book: "a feeling." What it feels like to be an intelligent animal.

A philosophy book as well as a book about animals and evolution.

The octopus (its neuro system / its brain) is not a survivor but a second expression (another expression) of what was present before. 

The best line: "The octopus is not Ishmael from Moby-Dick, who escaped alone to tell the tale, but a distant relative who came down another line, and who has, consequently, a different tale to tell." 

Chapter 2: A History of Animals

Earth: 4.5 billion years old.

Life began: about 3.8 billion years ago.

Animals arrived much later perhaps one billion years ago.

For most of Earth's history, then, there was life, but no animals. A world of single-celled organisms in the sea. Much of life today goes on in exactly that form.

Eukaryotes: 1.5 billion years ago. 

They edge close to a particularly sense: vision, p. 17.

Ediacaran: a discussion begins on p. 28.

635 to 542 mya. Think jellyfish. Cnidarian stingers. On both sides of the Ediacaran divide.

Cambrian explosion: began around 542 mya. (Does it matter whether it was 542, 550 500, 600 mya?)

Cambrian: the beginning of predation, p. 34. 

An "arms race" began.

But also another revolution: bilaterians, p. 34.

Possibly existed in the Ediacaran but unstoppable in the Cambrian, p. 35.  

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