The first part of this chapter explains the origin of new species as the result of the evolution of reproductive isolating mechanisms. I stress the fact that speciation is in no way a "goal" of evolution, but, rather, the secondary result of the processes of evolution (discussed in the previous chapter) producing genetic variation between an isolated portion of a species and the parent species. Populations may be reproductively isolated by a number of differentiating traits operating at different levels. I introduce the idea that speciation may be a relatively rapid event if isolation is the result of a macromutation.
The result of speciation and the subsequent action of the processes of evolution is adaptive radiation, which accounts for the diversity of the earth's life. Examples are given of different cases of adaptive radiation, including that of the primates, to be discussed in more detail in Chapter 10.
The tempo of evolution—the pace of change within species and the speed and frequency of speciation—determines the overall shape of life's family tree. The basic model of punctuated equilibrium seems to best fit what we know about evolution—essentially, that evolutionary change is the result of speciation rather than change within species. At the same time, individual species do change, although they tend to do so around an adaptive norm.
Finally, I return to the theme of science by looking at the pseudoscience of "scientific" creationism. I define pseudoscience, give several examples, and then show how "scientific" creationism is a perfect case. It is also, I point out, an example of the purposeful promotion of a pseudoscience by a small group who know exactly what they are doing and who have rather clear ulterior motives for doing so. I have now added “intelligent design,” a thinly disguised form of creationism, to the discussion.
