In 1964, The Rolling Stones recorded “Time is on My Side.” Evolutionary biologists continue to sing this song today with the latest rendition coming from Richard Dawkins in his newest book, The Greatest Show on Earth. In it, Dawkins presents what he thinks is the best evidence for the evolutionary paradigm.
I am currently working on a chapter-by-chapter response to the case Dawkins presents for biological evolution in his latest work. (Go here and here for comments on chapter one, and chapters two and three, respectively.) This week I continue my critique, focusing on chapter four and Dawkins’ assertion that the vast history of the Earth provides sufficient time for evolution.
In the first few chapters of his book, Dawkins argues that species are not fixed entities, but malleable, capable of being shaped by the forces of artificial and natural selection. Even though the observed changes to species are relatively minor on the time-scale of human history, Dawkins (and other evolutionary biologists) commonly argue that microevolutionary changes can generate dramatic evolutionary transformations if given enough time. Time is on evolution’s side.
This chapter argues that enough time does exist for evolution’s mechanism to generate life’s diversity. Dawkins spends most of the chapter describing methods scientists use to date the age of the Earth and of fossils, focusing mostly on radiometric techniques. Accordingly, Dawkins’ reasoning in this chapter goes something like this:
- The Earth is old (about 4.5 billion years old).
- Life is old (life has been present on Earth for at least 4 billion years).
- There is enough time for evolution to have transformed life in a step-wise, gradual fashion from single-celled entities to the diversity of complex life-forms on the planet today.
- Therefore, evolution is a fact.
I found this chapter quite disappointing. Not so much with the quality of Dawkins’ argument for the antiquity of Earth (with which I happen to agree), but with his use of straw man tactics. Dawkins creates the perception that people who question the evolutionary paradigm are singularly young-earth creationists who believe that the Earth is about 6,000 years in age. And all he has to do to is demonstrate that the Earth is old in order to respond to the challenges that these creationists level against evolution. He ignores the fact, however, that a number of intellectuals have serious doubts about the capability of evolutionary processes to exclusively account for life’ history and diversity, yet at the same time accept the scientific evidence for an old earth. In fact, there are a number of creationists who think that the best biblical interpretation of Genesis 1 is fully compatible with an old Earth. (See Hugh Ross’s A Matter of Days for the biblical and theological case for an ancient Earth.)
This straw man approach creates a diversion from the real issue. The question is not how old the Earth is or even how much time is available for evolution to work. The question has to do with the capability of evolution’s mechanism. Can the mechanism that undergirds microevolutionary changes and speciation be extended to macroevolutionary transformations? We simply can’t assume that the answer is yes because of the antiquity of the Earth. As I pointed out last week, there does appear to be boundaries beyond which species can’t evolve.
In my view, we can’t really answer this key question because we lack a fundamental understanding of how changes in genotype relate to changes in phenotype. This is one of the central questions in modern biology. Until this understanding emerges, there is no way to know if the mechanism that explains microevolution and speciation can be applied to macroevolutionary transformations.
Currently, field studies and the fossil record represent the best way to assess the capability of evolution’s mechanism. Do we see evidence for microevolutionary changes operating over vast periods of time to effect macroevolutionary transformations in the fossil record? To date, the answer appears to be no.
It seems to me that the evolutionary paradigm is running out of time.