Post Author: Bill Pratt

I have followed the intelligent design (ID) movement for several years now and there is an error that I’ve seen opponents of ID make over and over.

The error is confusing the idea of common descent with the idea of random mutation and natural selection.

Common descent refers to the idea that all animal life is related, that if we trace back each living animal’s ancestry, we would find common ancestors.  If every animal could trace back its family history through ancestor.com, we would all find that we came from the same great, great, great (insert great thousands or millions of times) grandparents.  Some of us are closer relatives than others but we are all related if we go back far enough in history.  The idea of common descent can be supported by evidence from the fossil record and by comparing the DNA sequences of different kinds of animals.

The idea of random mutation and natural selection attempts to explain how animals have changed over time into all the diverse species we see today and in the fossil record.  Every time an animal reproduces, there is a chance for a genetic mutation occurring in the process.  If the mutation that the offspring inherits is helpful to its survival until it, too, can reproduce, well then the mutation is passed on to the next generation, and so on.

In this way, the genetic code is altered, and if enough of these mutations occur over time, you get a new species of animal.  The empirical evidence for this mechanism only demonstrates very small, and in many ways, trivial instances of change (e.g., finch beaks, peppered moths, antibiotic resistance, fruit fly mutations).  There is no empirical evidence of large scale evolution due to random mutation and natural selection (see Michael Behe’s The Edge of Evolution and my recent post on this topic).

Which idea does ID challenge?  Common descent or the mechanism of random mutation and natural selection?

ID theory almost exclusively addresses the mechanism of random mutation and natural selection, not common descent.  ID challenges the idea that complex, specified biological systems can develop through random mutation and natural selection.  Regardless of this fact, time and again, opponents of ID throw evidence of common descent at ID proponents, only revealing their ignorance of ID.  Just recently on this blog, as I was discussing the lack of empirical evidence for random mutation and natural selection, I was treated to commenters’ arguments again for common descent; the error seems pervasive.

It is time that we understand the difference between these two ideas.  I would love to hear good arguments against ID theory, but first ID opponents actually need to do some reading and try to understand what they are opposing.  Almost 9 times out 10, when I read opponents of ID, they badly  misunderstand the theory.  If anyone can point me to actual ID opponents who understand ID, I would much appreciate it.