American Scientist

Sudden Origins: Fossils, Genes, and the Emergence of Species. Jeffrey H. Schwartz. 368 pp. John Wiley and Sons, 1999. $27.95

Evolutionary biology is a catchall term for questions of evolution and is thus composed of many splinter groups, such as paleontology and genetics. A geneticist will look at dominant or recessive characters, alleles or regulatory genes, and a paleontologist will identify not only extinct and extant species but also their changes over long periods. Despite their apparent dissimilarities, especially in their language, they are rather dependent on each other for illuminating and interpreting the whole question of evolution. The essential question of how visible morphology of a species changes (genetics) into a new species (as illustrated by the examples of paleontology) continues to haunt evolutionists. Jeffrey Schwartz's Sudden Origins is a worthwhile attempt at bridging the new developments in how species may change and the evidence for the patterns of those changes.

Sudden Origins relates how our species came to terms with its long evolutionary lineage. It is one thing to think of other creatures evolving, but when Neanderthals were first described, they were the first extant species to be labeled hominid. This not only immediately led to the search for other pieces of our evolutionary tree, but it also placed in our lap the importance of how we define a species and how a species may evolve. After summarizing the development of the paleoanthropological record, Schwartz's discussion shifts to the development of possible mechanisms of evolution.

Much of this is a history lesson in genetics, from Gregor Mendel and the problems that Darwin and his cousin Francis Galton had over panagenesis to the seeming discordance that such early geneticists as August Weismann and Hugo de Vrie had over gradual evolution. Reconciliation between genetics and evolution began with the ground breaking work of William Bateson on inheritance, among others.

There were of course others who combined laboratory manipulation of heredity characters with mathematical speculation, including Sewall Wright, John Haldane and Ronald Fisher. By the 1940s, paleontologists began to acquaint themselves with the techniques and results of geneticists and the latter to familiarize themselves with the stratigraphy and methodology of paleontology. This was (and still is) imperative for both.

As Schwartz points out, patterns could be seen in the fossil record, but how quickly morphological change happened was still in question. It is here, in the final chapters, that the author pushes the importance of homeobox genes, which "regulate an organism's development by way of sending signals from one to another in the form of the protein it produces." This then determines an organism's development. And since the switching of these genes is random, or "chanced," the organism will find its characteristics either suitable or not suitable to its surroundings. These sudden genetic shifts resulting in morphological change would not necessarily show up in the fossil record. The often sought after links "probably did not exist."

In order to bridge any gap, an individual must take steps toward new or seemingly obscure regions of thought. Most would find this recent intellectual bridging a decent first step.—Tim Tokaryk, Eastend, Saskatchewan, Canada