8 ideas
Sophisticated active bodies requiring some measure of intelligence arose separately in arthropods, cephalopods, and vertebrates, after these lineages diverged from a common ancestor that had at most a few simple nerve cells. This makes the cephalopod path an independent experiment in building a mind, not a variation on the vertebrate template.
Octopuses recognize and respond differently to individual human keepers, spray disliked people with water, and manipulate their environments with apparent curiosity and mischief. Reading these idiosyncratic, person-specific behaviors as signs of inner experience treats consistent individual reactions as a window into other minds.
Because the last common ancestor of humans and octopuses was a tiny worm-like animal roughly 600 million years ago with little more than a simple nervous system, any complex cognition in octopuses evolved separately from ours. Meeting an octopus is therefore the closest we can come to meeting an intelligent alien, and comparing the two lineages shows which features of mind are contingent and which recur whenever evolution builds large brains.
About two-thirds of an octopus's roughly 500 million neurons sit in its arms, not its central brain, and severed or unattended arms can still grasp, taste, and carry out reaching motions on their own. Octopus behavior is thus a mix of top-down direction and local arm-level control, a form of embodiment where the boundary between 'the mind' and 'the body' is genuinely blurred.
Giant cuttlefish send rapid waves of color and pattern across their skin, yet most cephalopods appear to be color-blind, having only one type of photoreceptor. Their skin may sense light directly with the same opsin proteins used in eyes. Much of the display may also be a leaky readout of internal state, an expressive channel that goes beyond deliberate communication and blurs the line between signaling and simply having a visible inner life.
Subjective experience did not flip on at one point in the tree of life but came in degrees, emerging as sensing and acting were bound together into an organism with a point of view. The rise of active, mobile bodies during the Cambrian, with animals that had eyes, pursued prey, and fled predators, created feedback loops between action and perception that pushed this gradual deepening of experience.
Inner speech is a way of producing a signal and then taking it in as input, the same way we hear our own voice. Using Vygotsky's work, the author presents it as an evolved tool for combining information and regulating behavior, a feedback mechanism that may help explain the integrated, narrative quality of human experience compared with octopus experience.
Octopuses have large brains and learn quickly yet typically live only one to two years, which appears to waste the investment in intelligence. Following the evolutionary theory of aging, the author argues that high predation historically selected against long life: mutations with harmful late-life effects accumulate because few individuals survive to express them, so a big brain was built for a complex body and foraging life, not for longevity.