The book is in four parts: 1 – The Simple and the Complex, 2 – The Quantum Universe, 3 – Selection and Fitness, and 4 – Diversity and Sustainability … and most of those words are not used in the way you think they mean … “complexity”, “fitness”, “diversity” all are based on really obscure mathematical theories and Gell-Mann jumps right into the thick of that in most of these, leaving behind (I'm guessing) most readers until he comes back out to the broad-stroke discussions.
The first part is particularly hard to wrap one's head around … here are some cherry-picked section headings: “Complex Adaptive Systems”, “Information and Crude Complexity”, “Indeterminacy from Quantum Mechanics and from Chaos”, “Context Dependence”, “Conciseness and Crude Complexity”, Algorithmic Information Content”, “The Uncomputability of AIC” (see previous header), “Compression and Random Strings”, “Random or Pseudorandom?”, “Complex Adaptive Systems and Effective Complexity”, “Falsifiability and Suspense”, “Scale Independence”, “Depth and Crypticity”... I suspect that you'd be surprised to find that, in the course of those, markets, sub-atomic particles, infants acquiring language, the predictability of place names, the inter-relation of chemistry and biology, etc., were all looked into in a reasonably lively manner.
The second part is pretty straight forward (OK, so as straight forward as quantum stuff gets!), but it's dense … to illustrate this, take a look at this bit from the “Decoherence for an Object in Orbit” section:
... simple, right? Not too many pages after that he's talking Schrödinger's Cat, and then introducing his model of a complex adaptive system – IGUS – information gathering and utilizing system (which said cat could be argued to be), and thence into “Self-awareness and Free Will” (this is still in the discussion of quantum effects). Since Gell-Mann is the originator of the Quark, this heads off in that direction too, with discussions of QED, QCD, Gluons, Neutrinos, the varieties of Quark, assorted violations of symmetry, SuperString theories, stuff in the Planck scales, multiple universes, forward and backward time, etc. Fun stuff … no, really … it's always great to hear some guy who actually “gets” this stuff riffing on it.Say the object in orbit has mass M, the linear dimensions of the small regions of space are of order X, and the time intervals are of order T. The different possible coarse-grained histories of the object in the solar system will decohere to a high degree of accuracy over wide ranges of values of the quantities M, X, and T. The mechanism responsible for that decoherence is again frequent interaction with objects the fates of which are being summed over. In one famous example, those objects are the photons composing the background electromagnetic radiation left over from the initial expansion of the universe (the so-called big bang). Our orbiting object will repeatedly encounter such photons and scatter off them. Each time that happens, object and photon will emerge from the collision with altered motions. ...
You might expect that the “Selection and Fitness” part is where the titular Jaguar comes in … well, yes and no. The chapters here go: “Selection at Work in Biological Evolution and Elsewhere”, “From Learning to Creative Thinking”, “Superstition and Skepticism”, “Adaptive and Maladaptive Schemata”, and “Machines That Learn or Simulate Learning” … a lot of ground gets covered here! The author asks “Is There A Drive Towards Higher Complexity?”, borrows terminology more familiar from Multiverse theories to look at “Fitness Lanscapes”, name-checks Dawkin's “The Selfish Gene”, charts out chromosomal cross-over, considers population biology, talks about the “incubation” of ideas (the middle phase of Helmholtz's model), and “boundaries” of problems. The “Superstition and Skepticism” chapter is very interesting, although being, as one might have guessed, a bit skewed to the skeptical.
The last section is a bit of soap-boxing on the part of Gell-Mann, advocating actions and policies for both cultural and environmental diversities. While some of this is no doubt “evergreen”, based on the material that precedes it, being a decade out at this point, there's been a lot of unanticipated change (or perhaps the absence thereof), which throws this off. There is a nice summation about where the book has been up to that point, however, which I think is useful:
Again, The Quark and the Jaguar is not exactly an easy read, nor a particularly coherent one (in his efforts to pull so many things together, there is a quite a bit of jumping around), but it can't be said that it's not an interesting read, and it is bursting with data points that will surprise and amaze (I doubt there are a lot of readers out there whose knowledge spans what Gell-Mann has crammed in here). So, with the caveat that it's a good bit of a slog, I'd recommend this to those willing to expend the effort. Tellingly, this is still in print (perhaps it's used as a college text?), and the big boys have it on-line for a bit off of cover. However, since it has been out for a decade, the new/used guys have copies for as little as a penny (if I recall correctly I got my copy from either the Newberry Library Book Fair, or one of Open Books' awesome "box sales"), so you can pick it up without too much of an investment.We have examined how simple rules, including an orderly condition, together with the operation of chance, have produced the wonderful complexities of the universe. We have seen how, when complex adaptive systems establish themselves, they operate through the cycle of variable schemata, accidental circumstances, phenotypic consequences, and feedback of selection pressures to the competition among schemata. They tend to explore a huge space of possibilities, with openings to higher levels of complexity and to the generation of new types of complex adaptive system. Over long periods of time, they distill out of their experience remarkable amounts of information, characterized by both complexity and depth. … The information stored in such a system at any one time includes contributions from its entire history.