Science in Christian Perspective

Letter to the Editor



Response to Kuehn

Robert F. DeHaan, ASA Member

7714 McCallum Street
Philadelphia, PA 19118-4308

From: PSCF 51 (June 1999): 139.

Monica Marcinko Kuehn raises two major concerns in her letter: (1) the need for PSCF to be a peer-reviewed journal and (2) the content of my article, "Do Phyletic Lineages Evolve from the Bottom Up or Develop from the Top Down?"

With regard to the first concern: My article was reviewed by two anonymous referees who provided criticism and suggestions. Also, before completing the final draft, I sent the manuscript out to two other readers for additional comments and criticisms.

Kuehn mentioned a second set of concerns about my article. The article is "contentious." That depends on one's point of view: to a confirmed evolutionist, probably yes; to someone who is dissatisfied with the Darwinian paradigm and who is open to alternative exceptions, probably no.

Moreover, the naturalistic explanation of evolution held by scientists whose research I cited was not threatened by their research showing the top-down direction of change in phyletic lineages. Of course, it wasn't. Yet their research is not cited in standard evolutionary literature because it does not fit the dominant paradigm But that's not what is important. What is important is that their findings are open to an alternative explanation, which I attempted to provide. My explanatory theory lies within naturalistic boundaries of science.

Kuehn stated further: "The diversity of life on earth does not fit the body-plan view of life." I am not discussing diversity. I am dealing with the hierarchical organization of life, as I emphasized. That life is hierarchically structured is recognized by evolutionary authors, notably Dobzhanskv. The fossil record shows that phyla originated in with the body plans of individual Cambrian animals which established the top-down structure of the phyla.  Everything that followed historically in a given phylum occurred at successively lower hierarchical levels.

This top-down hierarchical shape of a phylum has an uncanny resemblance to the top-down process of develoment in the embryo and early stages of individual development. This suggests that developmental processes were at work in the formation of phyletic lineages. Diversification through natural selection came later to enhance the adaptiveness of the hierarchically structured animal group.

Kuehn admits that the "origin of many evolutionary novelties has yet to be adequately explained." She asks how I account for the origin of the ftmdamental phyla found in the Cambrian explosion. My article did not address this question. My purpose was to show that the later post-Cambrian history of the phyla cannot be adequately explained without reference to developmental processes. So what's the problem with my offering an alternative, non-Darwinian developmental explanation? I invite Kuehn and others to compare the evidence for a phyletic developmental theory and the prevailing Darwinian theory of how phyla changed over geologic time after the Cambrian explosion as presented in my article.