Chris Rollins has a great post on Emergent Behavior on Scientific Blogging.
He makes a great series of points hear about the relationship between emergent behavior and entropy, and how they can possibly coexist:
Emergent behavior, or the spontaneous creation of order, is present all around us. Insects are a good example because they are familiar to us and manage to undertake massive building projects which we can appreciate. Other parts of the animal kingdom also display autonomous order – fish organize themselves into schools that move in concert; birds and pack animals flock or herd in a similar manner. And nonliving examples also abound – natural magnets align themselves into a common North-South orientation and crystals can form from liquids, showing a spontaneous increase in order despite the lack of a more “intelligent” force.
There’s a major thermodynamic problem with all of this, of course – entropy, a measure of disorder, is supposed to continually increase. The universe tends toward chaos.
How, then, can spontaneous order arise, especially in a purely physical system?
Entropy still must increase, even when crystals form or birds flock, but the important distinction is in where the entropy increases or decreases. It turns out that nature will allow entropy to decrease in certain areas provided that it increases elsewhere to compensate. For instance, when a sugar solution begins forming crystals those crystals have a net lower energy level than the free-floating molecules of sugar in the solution. When the sugar enters the structure, it loses energy that is transferred to the water in the form of heat: the most disorganized form of energy.
Therefore, the crystalline portion of the solution has now decreased in entropy while the total system – including the water and the crystal – has had a net increase in entropy.