A portion of Douglas J. Futuyma’s textbook Evolution is available on the web – the chapter that describes natural selection and adaptation. The NCSE describes Futuyma as the “Distinguished Professor in the Department of Ecology and Evolution at the State University of New York at Stony Brook.” In other words, he is a highly respected, mainstream evolutionary biologist. His textbook (the linked chapter is from the second edition) is a widely used, mainstream text on evolution which was reviewed by dozens and dozens of other scientists. While it may seem trivial to point this out, we will soon see it is a very important consideration.
I want you to consider a key excerpt from the text, entitled Design and mechanism:
The complexity and evident function of organisms’ adaptations cannot conceivably arise from the random action of physical forces. For hundreds of years, it seemed that adaptive design could be explained only by an intelligent designer; in fact, this “argument from design” was considered one of the strongest proofs of the existence of God. For example, the Reverend William Paley wrote in Natural Theology (1802) that, just as the intricacy of a watch implies an intelligent, purposeful watchmaker, so every aspect of living nature, such as the human eye, displays “every indication of contrivance, every manifestation of design, which exists in the watch,” and must, likewise, have had a Designer.
Supernatural processes cannot be the subject of science, so when Darwin offered a purely natural, materialistic alternative to the argument from design, he not only shook the foundations of theology and philosophy, but brought every aspect of the study of life into the realm of science. His alternative to intelligent design was design by the completely mindless process of natural selection, according to which organisms possessing variations that enhance survival or reproduction replace those less suitably endowed, which therefore survive or reproduce in lesser degree. This process cannot have a goal, any more than erosion has the goal of forming canyons, for the future cannot cause material events in the present. Thus the concepts of goals or purposes have no place in biology (or in any other of the natural sciences), except in studies of human behavior. – (p. 282; emphasis not added).
Let’s pull out the key point to make it crystal clear: