> Regardless, my question is why did consciousness arise? What was the need?

I have my own theory that explains what, why, and how. First, there is no singular consciousness, that's an illusion created by only one part of the brain having an internal verbal monologue. I think that we are actually a collection of smaller consciousnesses working in concert.

We have the reptile brain for basic functions, it's aware of being hungry and sleepy, etc. It also takes care of basic memory storage and emotional imprinting. It's the oldest brain, evolved as a simple logic operator, where it evaluates an input, and then triggers a response. Hungry? Look for food. Scared? Run. Etc. It learns and stores memories too. I nearly got eaten when I went over there, scary, tag that place memory with a bad feeling.

Then we have a more advanced mammalian cognition level, where more advanced behaviors came from, more complex memory indexing making the reptile brain more useful for long term storage and more nuanced learning. Daytime over there is fine, night can be scary. Oh, that scary thing over there is actually safe, but let's be careful there anyway. More advanced social interactions, forming packs and such with social hierarchies.

Now we also have a more advanced logical component and pattern matching ability. A rustling of that specific type of bush tends to mean there's a lion in there. When I see dark clouds, I should find shelter because water might fall. I can take this stick and push it in this anthill to get ants, or I can take this other stick and knock down fruit I can't reach. Rocks from over here chip really well when I bang them together the right way, and I can use the result to cut things. Now we see high order logical cognition emerge.

That leads to a part of the brain that helps coordinate the other parts of the brain leading to the ability for abstract thought, symbolic thought, and internal monologue for enhanced creative thinking. This part of the brain is what we think of as "us", our "mind" but it's just a part. Other parts aren't as verbal. That's why sometimes ideas "just come to you", and something you can't quite recall is on the tip of your tongue, another part of the brain was working independently, and pushed that information over to your forebrain, or your forebrain remembers a trigger for a memory, but the memory part isn't quite picking up on the index cue. It's why we "sleep on things", or go for walks and need time to think, we're letting our various parts work independently so they can not worry about communicating with each other for a bit and focus. It's why you get "in the zone" when you're really productive, and it's even why we go on "autopilot" and get home but don't remember the drive, our forebrain shuts up for a bit, or is naval gazing and the other parts took over the drive.

I'm not saying these are the only parts, but ever since reading Marvin Minsky's "Society of Mind" and learning evolutionary physiology it's a concept that made a lot of sense. I don't think it's all as subdivided or mindless as Minsky think, but I REALLY think is over all concept is dead on.

In short, consciousness doesn't arise FROM anything, consciousness is what the brain is doing. It's not a side effect, it's the main one. We just think it's special and different from animal cognition because we have language. We think and feel just like dogs and cats and elephants, just in a more complex fashion.