The birth of this volume was a symposium on the same subject at the University of California, Los Angeles, in 1977. That this title has come along so many years later is a blessing, presumably to be attributed to the editors. For once, the papers from a symposium have been rewritten, reviewed, and assembled with the idea that a collaboration can be coherent and cohesive. One would not expect fifteen writers to agree on everything — they certainly do not — but at least they are discussing the same region and addressing some of the same issues.