I previously blogged about V. A. Firsoff's Life Among the Stars, which, among other things, explained how tree octopuses may one day become a spacefaring species. Life in Darwin's Universe (1981) by Gene Bylinsky, with illustrations by Wayne Mcloughlin, covers similar ground, asking what shape intelligent life elsewhere in the Universe may take under Darwinian constraints using Earth species as analogies. Of course it includes octopuses.
Bylinsky doesn't propose arboreal octopuses as candidates for likely Star Fleet founders. (He references Firsoff's work, so he must be aware of Firsoff's Out of Trees theory of cephalopodic space exploration, but doesn't mention it.) At first he considers octopuses as analogues to inhabitants of landless waterworlds, who would develop radial symmetry and eventually converge to the octopus bauplan. Still, he does allow for some alienness:
Of all the marine beings, an octopus-like creature would have the best chance to emerge as the ruler of an ocean kingdom, becoming the kind of superoctopus shown in our illustration. This king of the seas could have two telescopic eyes looking upward to the light and surface of the sea. Around the middle of its head, it could have a ring of large camera eyes. It could have as many as twenty or forty tentacle arms, each subdivided into three tapering, flexible fingers. Tentacles as long as one hundred feet would be needed to catch crabs and other delicacies. When coming close to each other, the giant octopuses would communicate by rapidly changing their colors.
Elaborating on the octopus's reputation for intelligence, he recounts Jacques Cousteau's discovery (taken from Octopus and Squid: The Soft Intelligence,) of "Octopus City" -- a collection of "houses" built by octopuses off the coast of a Mediterranean island -- and imagines extraterrestrial octopuses creating even more complex construction:
Lastly he brings up land octopuses, arguing that they would, like other large terrestrial animals, evolve toward four-leggedness should they take up land-walking under the effects of Earth-like gravity -- much to their advantage:
In a land-dwelling octopus, such capabilities [coordinated movement of multiple arms for different purposes] could be significantly enhanced. Such a creature could walk on four arms, which would turn into legs, and have four additional arms free for manipulating objects. Already displaying a prodigious talent as a builder, a land-dwelling octopus could become a real architect.
While not even the sky is the limit for such four-armed go-getters, Bylinsky notes that octopuses might have other priorities, perhaps more sensible than our own:
With its arena of stimulation widened spectacularly, a land-dwelling octopus could develop a large brain and engage in activities that would be unthinkable in the sea. Aside from becoming a skilled builder, it might master fire-making and even start a technological civilization. But such a leap is not entirely necessary for an intelligent creature. The land-dwelling octopus, therefore, might choose not to advance higher technologically than, say, becoming a highly skilled gardener. Lack of technological prowess, of course, is not a mark against a creature's intelligence. It might actually be a big plus where its continued survival as a species is concerned, since its means of destruction would be limited.
Bylinsky's book is (unfortunately!) not entirely about octopuses and their potential rise to interstellar greatness. Like Firsoff, he explores other species' likelihood of intellectual advancement had historical contingencies worked out differently, as they certainly have on other planets. For instance, had the savanna not given upright distance walkers like humans an advantage, perhaps our flying cousins, the bats, would be running the place:
Bat-men could have become dominate creatures on Earth. Both men and bats stem from the same ancestor, a shrewlike mammal. The reason man emerged was the opening of the savannas due to geological and climatic reasons. Had the grassy plains never appeared, the bat would have been favored over man to emerge as the Earth's dominant animal. That sequence could have happened on other worlds.
(See my synopsis of Gerald Heard's short story The Lost Cavern for a take on a bat-men society living alongside that of human-men.)
On another alternate Earth, placentals might not have surpassed marsupials, and the world would be ruled by hyperintelligent koalas, whose brains could balloon as large as needed without the head-size constraints of the placental birth canal:
MARSUPIAL MEN—Humanlike creatures can develop elsewhere from koala-bear-like ancestors. Marsupial females are equipped with pouches in which they rear their prematurely born young—a big advantage for evolution of large brains. Marsupial manlike creatures like those in our illustration could easily have evolved on Earth if marsupials had dominated the other theaters of life as they did Australia.
The fairly narrow birth canal of human females may block the further evolution of man's brain. At birth, our heads are already so large that they barely fit through the pelvic opening. If the brain is to grow further, future man must either enlarge the birth canal or manipulate the developmental processes so that the brain can continue to grow long after birth. Our marsupial cousins, though, could grow much larger heads, with brains like those Dale Russell projects for man nine hundred thousand years from now. The marsupial female [below] may strike us at first as very odd, but her children may be unimaginably ahead of us in intelligence and technology.
Bylinsky rewinds the tape of life further to consider reptiles and insects becoming the dominate intelligence. He also reviews concepts of "life as we don't know it" -- life without earthly analogues, e.g. "sulfur-breathing monsters with ammonia flowing in their veins" -- from science fiction and less rigorous scientific musings, and finds them wanting. He concludes that life out there must look much like life here, because the laws of nature demand it.
As is required whenever discussing intelligent non-human earthlings, dolphins are brought up. While Firsoff was pessimistic about their prospects beyond the seas due to their useless-for-all-but-swimming flippers, Bylinsky and Mcloughlin propose some sort of atavistic evolution (quoting Dr. N. J. Berrill for support, as Bylinsky does often throughout) that will enable cetaceans to make it onto land and into the trees, an important step on the path to the Cosmos:
"When you think that a fish fin became a walking leg and has now reverted to being a dolphin flipper, you can't say that a dolphin flipper couldn't in the course of a long time become reconverted into a walking leg, if the animal had a chance to get out of the water," says Dr. Berrill.
I think we see here an implied impetus for a tree octopus space program. Should these hunched dolphin-men clamber out of the sea and start eying the trees as their new home, arboreal octopuses would want to leave the planet as quickly as possible, rapidly flashing whatever skin color is associated with "nope".