I was listening to a science podcast the other day from which I learned that our brain took a big leap in intelligence when we started walking erect. The idea being that it freed up our hands. I realize that there is not a concensus on this matter but it seems reasonable.
But then it dawned on me that freeing up a beings hands is only helpful if that hand has fingers and an opposable thumb - that evolved from climbing trees. I’m not sure that walking erect would help a dog, for instance.
So if trees would never have evolved or if another planet with life never had climbing structures could advanced civilizations evolve? It would be hard to make a stone axe with a paw… much less a spaceship.
This is more opinion than fact but… Take a look at critters like octopi. They are believed to be extremely intelligent despite a lack of hands. It’s impossible to say that X or Y will always happen or never happen.
In general though, I agree with your point about the dog. If the animal’s strategy is “good enough” and they have no selective pressures that would cause them to evolve a certain kind of appendage, they are likely to stay in stasis.
Another species that has intelligence and an ability to manipulate objects would be elephants. The trouble with a sample of one - humans - is that it does not adequately show all options.
Wolves, feral pigs, and especially bears are also reputed to be fairly intelligent - an obvious necessary trait for any predator that doesn’t have an alternate gimmick (like a cheetah’s speed). Bears come close to front-paw maiplation capability.
Humans have a number of adaptions that allow for our extremely advanced levels of intelligence (for some of us). Upright let us use our hands to manipulate things; but also made us efficient long-distance runners for hunting. We learned to use tools to substitute for attributes we had not evolved - rocks and pointy sticks to take down animals we would not have been able to handle otherwise, fire and sharp rocks to subdivide and soften dead critters for chewing so we did not need fancy canines (the teeth, not the show dogs), herd action allowed us to collectively hunt much larger animals, that again, we could not take on single- or double-handed. That same herd socialization led to more elaborate planning resulting in bigger brains and better communication. The large amounts of meat we obtained this way allowed us to feed those bigger brains to support this intelligence (although some vegans seem to be trying to trend the opposite direction). In the end, we are a confluence of far too many convenient evolutionary choices.
Birds, for example, are bipedal - but other than penguins using wings as flippers, I’m not aware of any flightless birds who have wings evolved to be more manipulative of their environment.
OTOH plenty of species seem to climb around and swing from tree to tree without opposable thumbs so I’m not sure how that feature can be complete blamed on trees. It was either an accident of evolution that gave us an edge in the trees perhaps(?) or selection after trees when we began needing to get a better grip on our environment.
A couple of things. First, the hominid lineage became more terrestrial long before big brains evolved. Austrolopithicus afarensis (“Lucy”) was quite terrestrial (although still climbed trees) but had a brain not much bigger than a chimp.
Second, tree climbing is not the only reason to evolve opposable digits. Giant Pandas and Red Pandas have evolved “thumbs” of sorts just to handle their diet of bamboo. Raccoons are quite adept at manipulating things even without thumbs. Elephants and octopuses have appendages that can be used to manipulate that have nothing to do with tree climbing.
High intelligence is more associated with high sociality than it is with the presence of hands (as in dolphins). While some kind of appendage to dexterously manipulate the environment is necessary for technology, having one is not the only path to high intelligence. And there are other paths to acquiring such an appendage than climbing trees. So there is no necessary relationship between trees and technology.
And a relative of the bear - the panda - has evolved a “thumb” of sorts that makes it even more dextrous.
Don’t think raccoons are considered particularly close to bears, but their front paw are very capable despite not having thumbs. If dexterity ever becomes (more) advantageous to these guys they might evolve something like the panda’s solution, if not an outright opposable thumb. Or maybe what they have would be just good enough. Contrary to rumor, evolution doesn’t promote perfection, just workable solutions.
Birds don’t manipulate things with their wings. They use their feet. My parrots have four digits on each foot, and two of them oppose against the other two. They also use beak/foot combinations to hold and manipulate objects.
Crows are also known for their intelligence. Like most birds, they have one digit on each foot that opposes the other three and, again, also utilize their beaks. The Caledonian crow is know for tool use and even making crude tools as well as some very good problem-solving abilities.
The big limitation for birds is that flight is so costly in metabolic terms and requires so much specialization, and also requires a relatively small body size. Birds that gave up flight either then specialized for swimming/cold (penguin feet aren’t particularly dexterous) or running (ostrich feet are good for locomotion, crap for manipulating objects). Wings don’t seem to evolve into manipulators when that happens (penguins specialized them for swimming, in the ratites they atrophied, in some cases into near non-existence).
One statistic I heard is that 30% or so of our metabolic intake goes to feed our big brains. Therefore that organ better have a serious advantage in terms of food acquisition to compensate for the need.
One story is that early humans started off scavenging carcasses left behind by the big predators, and used rocks and sticks to drive off the other scavengers, and rocks to break open bones for more tasty treats. This evolved into using these weapons to bring down larger game; and fire to soften otherwise hard to digest raw meat.
Meat is an extremely concentrated source of protein, a very useful source of food - especially when it comes in 1,000lb packages wandering in large herds all over the plains. You gotta gather a LOT of beans and tubers over a long time with a lot of work to make up the equivalent nutrition.
Dolphins are pretty intelligent and they can’t climb trees.
Also another big factor in brain growth was fire. Fire allowed us to shrink our jaw muscles, which gave us more cranial space for larger brains.
Supposedly the big factor in intelligence is being a social animal. In social animals everyone is trying to take more from the group than they contribute, while also stopping others from doing the same. Also they are trying to figure out how to rise to the top of the social ladder since those positions involve better mating and feeding options.
I believe most intelligent species tend to have social systems. There are exceptions like orangutans.
Another interesting point about trees and evolution - supposedly we have two eyes side-by-side because the resultant local depth perception was important for hopping from branch to branch. This positioning gives us a better 3D perception of the workspace where we are manipulating things with our handy hands.
It is a mistake to assume that any particular feature of the evolutionary development of human sapience or cognition is an obligate step for general intelligence, and indeed, that the sapience or cognitive abilities of an alien species will look anything like human intelligence. In the generic scheme of the development of any kind of intelligence the only thing that can be assumed is some environmental pressure that gives advantage to general problem solving abilities and (possibly) social behavior and communication. Anything beyond that is purely an assumption based upon preconceptions of what a particular intelligence should look like.
We’re sufficiently intelligent as individuals to understand why destroying habitats and using precious natural resources beyond their sustainability is bad. We just lack the consensus on a societal level to exert the will to make choices that benefit the majority in the future rather than the easy decision today, which is less an artifact of intellect than of short term greed and gluttony of the leaders who run our institutional systems of governance and commerce. The appeal to “the market” as a solution for all ills is simply a naive assumption of inexperience rather than a lack of basic intellect.
A friend of mine once had a pet raccoon that probably could’ve been taught to deal cards. Can’t raccoons kind of use one of the digits on each forepaw as kind of a quasi-opposable “thumb”?
If there is no thumb, a thumb *can *be evolved- no tree climbing needed. But a thumb doesn’t make a species smart enough not to be on the verge of extinction from stupidity.
BTW, pandas do climb trees. Given their body size and shape, surprisingly well.
I think the OP makes an interesting point. Sure, dolphins, octopuses, elephants, etc. have a surprising amount of intelligence given our innate speciesism. But they never developed fire, sharp bladed tools, decent throwing spears, etc. A large part of those skills were possible due to the eons spent in trees developing brains, binocular vision and agile hands. Note that mere opposable thumbs aren’t enough. We had to develop a precision grip that no other primate has.
But we had to get out of the trees to get to the next level. E.g., being able to run for an extended period of time helped a lot. This allowed a diet that relied on meat eating (and then fire) which really changed our bodies so we didn’t end up like pandas.
#/media/File:Darwin_Tree_1837.png){kind=link}
