Pictured above is a sea squirt. What's fascinating about sea squirts is that, similar to a frog, they are tadpoles when they are young, but instead of growing legs, upon adulthood they root themselves into the ground and live the rest of their lives stationary as if they're plants. And as soon as that happens, they eat their own brain.
Why? Simply because once the squirt gives up on movement, snacking on its own brain gives more value than keeping it. Without the ability to move, a brain is worse than dead weight. This is a deep coupling of the mind and the body. It is a living demonstration of the fact that intelligence is only desirable if it's beneficial from an evolutionary standpoint.
Imagine if dogs were as intelligent as humans. Would there be dog civilizations? I don't think so. Humans are the most intelligent species by far for a reason. It is our hands that give us the ability to manipulate and our feet that make us bipedal, freeing the upper two limbs up, that gave rise to our intelligence.
This is an example of a whole field called "embodied cognition," the idea that our thinking is tied, functionally, to the way we move in and through the world.
http://blogs.scientificamerican.com/guest-blog/a-brief-guide-to-embodied-cognition-why-you-are-not-your-brain/
There are already canine civilizations in embryonic form. It's called wolf packs. If their intelligence were greater their civilizations likely be more complex. Crows have greater intelligence than wolves, in fact they are the equivalent to chimpanze's.
Yes, they do have civilizations. The flock. They do have a language and they do have an oral tradition from one generation to the next. In many ways Crows are similar to what humans were fifty thousand years ago. They are tool users also, moreso than Chimps. They even make their own tools to the extent that they can with their limited ability to manipulate.
If Crows were to be genetically engineered to have arm-hand-thumbs the potential would be interesting.
I'm fascinated by the potential. I write about it at @everittdmickey and publish sci-fi books
speculating about the myriad possibilities.
Visit sometime.