Indeed, it changes the world much more than expected. One of the head researchers makes a final breakthrough earlier than expected after years of performing his own experiments on the lab equipment after-hours. He manages to unexpectedly create something that is way beyond the bio-machines he had been working on for his company during normal work hours: he invents intelligent cells. These cells have been designed by him with the functionality needed to work together, evolve together, even - he finds - think together.

When his experiments are discovered and ordered terminated, he injects the intelligent cells into his bloodstream to smuggle them out of the lab. But soon they multiply, adapt and take over his body: millions, even billions of them spread throughout his body and develop into a sort of civilization within him, a galaxy of intelligent life within the body of one man. Soon, though, they discover the universe that lies outside of that man, and they spread there too.

This setup is intuitively implausible. Evolution selected a pretty efficient design for our brains, but it still takes a hell of a lot of neurons to get the conscious intelligence we have in our skulls; so how plausible is it that a cell or even a cluster of one hundred cells could be as intelligent as a monkey (which Bear says at one point)? Fortunately he provides a more plausible explanation later on, but I will not spoil the book by getting into that. Needless to say, these 'noocytes' multiply magnificently and pretty soon they make up a gigantic hive-mind of sorts (though full of semi-distinct personalities).

At one point, a character named Bernard is contemplating the offer by the noocytes to have his brain - his memories and mind and personality - copied by them, transcribed into their mode of existence and spread throughout their civilization-mind. Basically, they offer to upload his consciousness into their hive-mind and copy it around, preserving him throughout their civilization even if one copy gets destroyed. Here's an excerpt of his thoughts on the matter which I rather enjoyed:

In North America-what happened to all the bad people whose memories were preserved by the noocytes? They were, to be sure, suspended from the world in which they had been bad just as surely as if they were in prison-far more suspended. But being bad meant bad thinking, being evil meant being a cancer cell in the society, a dangerous and inexplicable screw-up, and he was not just thinking of ax murderers. He was thinking of politicians too greedy or blind to know what they were doing, white collar sharpies who had swindled the life's savings from thousands of investors, mothers and fathers too stupid to know you shouldn't beat your children to death. What happened to these people and to the millions of screw-ups, evil screw-ups, in human society?

Were all truly equal, duplicated a million times, or did the noocytes exercise a little judgement? Did they quietly delete a few personalities, edit them out...or alter them?

And if the noocytes took the liberty of altering the real screw-ups, perhaps fixing them or immobilizing them some way, going into their thought processes and using a kind of grand consensus of right thinking as a pattern for corrections.

Then who was to say they weren't altering others, people with minor problems, people with all the complexes of little screw-ups and errors and temporary nastiness...things all humans have. Occupational hazards of being human. Of living in a tough universe, a different universe than the ones the noocytes inhabited. If they did correct and edit and alter, who could say they were good at it? Knew what they were doing, and retained workable human personalities afterward?

What did the noocytes do with people who couldn't handle the change, who went crazy? [...]

Would there be conflict, revolution?

Or would there be profound quiet-the quiet of the grave, because of a deletion of the will to resist?[...]

Bernard, do you now feel the fear of Big Change? The completely different-sublime, or hellish-as opposed to the difficult, often hellish status quo?

This is a problem for those transhumanists who see uploading as a solution to personal mortality. The chance that you could remain you inside a hive-mind of some sort seems doubly slim; even if there is no conscious editing by the hive-mind consensus, surely simply existing in that new way would change the very way you perceive and think and understand. Surely it would change you and you would no longer exist as the same person who chose to upload your consciousness. Instead, you would likely merely register as a slight blip on the hive-mind's internal representation of itself, lead to a few minor changes perhaps, but the hive-mind would balance out soon after, very little changed by your presence; and no longer would you be you.

This is why hive-minds, as cool as the concept is, do not present a solution to personal mortality. The 'Big Change' Bernard is talking about in the excerpt above is not the change of the world as the noocytes spread and reshape it; it is not even the change of his location from a physical human body to a distributed intelligence across a vast network of cells. The change he is pondering is personal death. It is taking the step to a new existence, but by definition he cannot continue to exist as he does after he takes that step. So what he would be doing by joining the noocytes is suicide, but suicide in which somehow his experiences and memories resonate and add to a bigger collective (like memes spreading through a society today). It is a form of influencing the future, of merging into it, into something bigger, but it is not personal immortality.

That, I think, is why we fear the 'Big Change'. Not because the Borg seem to lead such boring lives as drone-slaves, but because when a person joins the Borg, they cease to exist as the person they were before. Hive-mind existence is death for individual minds. But at the same time, something bigger goes on, and contributing to that in some way could be seen as living on in the same way authors can live on through the centuries through their books. The authors may not be around, but they have achieved a different sort of immortality: they have made an impression on the world.

Indeed, we are all doing that each and every day with all of our actions. The littlest action can have great consequence through chaotic effects (like a butterfly flapping its wings and eventually altering weather across the glove). If it turns out that humanity someday goes the way of the Dodo and something completely different (like a hive-mind) replaces us, then perhaps we can take solace in the fact that though we personally die out in 'joining' it, the minor influence of our integration might influence things in unknown, amazing ways. And that seems pretty cool, even if we aren't around to enjoy it, because someone or something will be.