Terry Gray wrote (20 February) in response to Stephen Jones:
TG: "This raises an interest question that I pursued with one of
our philosophers here at Calvin. Do similarities and the nested
patterns found in biological world support common design and
common ancestry equivalently? I've always been willing to grant
that they support both positions equivalently and that my
preference for common ancestry is due to other knowledge of
genetic and other biological processes. To my surprise, he said
no and gave all sorts of reasons why the common ancestry
hypothesis was to be preferred from a philosophy of science point
of view".
This is an interesting question - particularly because of the way
predictions are said to emerge from the differing perspectives
of the natural world. I am conscious that the issue is addressed
by Kurt Wise in his chapter on "The origin of life's major
groups" in _The Creation Hypothesis_, J.P. Moreland (ed), IVP,
1994. Kurt has four points on pages 217-221. I would be
interested to get reactions to them. To assist interaction, I
am paraphrasing Kurt in what follows.
The nested hierarchy of biological form has been linked with
"common ancestry" using the analogy of the "evolutionary tree".
This is scrutinised in the four points below.
1. The analogy with real trees breaks down, as there is a strong
tendency for the twigs and outer leaves to occupy most of the
space available to them. This is not so in the biological world:
"most of the morphospace is unfilled". Kurt considers various
options for explaining these observations and concludes: "It is
unclear that any currently proposed macroevolutionary process
could truly produce a nested hierarchy of form".
2. The tree analogy also breaks down when examining the overall
morphology of the trunk, branches and twigs. By analogy, the
various groups of organisms are predicted to have arisen by
gradual divergence. However, there is not a convergence in
morphology in organisms as one goes back in time. "Most major
groups remain identifiable by modern characters". Evidence for
branching events is therefore highly controversial.
3. In real trees, the trunk/branch connections and branch/twig
connections can be clearly seen. Transitions between major
groups of organisms are controversial and rare.
4. As a real tree grows, the number of branches and twigs
increases with time, with twigs increasing in number faster than
the branches. This has been described as a "cone of increasing
diversity". This however, has not been observed as far as major
groups are concerned - earth history has seen a LOSS of major
groups with time! (cf Gould's _Wonderful Life_).
Kurt contrasts the lack of evolutionary explanations for the
observations with that supplied by ID. By analogy with human
creativity, a nested hierarchy is expected. Based on this
analogy, all the major features of the fossil record outlined
above can be readily explained. "And if the gaps between major
groups were so large that speciation has had insufficient time
to bridge them, the general stasis of major groups and the marked
nested hierarchy of biological form through time would be an
expected result".
TG: "Unfortunately, I wasn't taking notes, so I can't remember
all of the details. But part of his argument had to do with what
sorts of questions one could ask of each model and what sorts of
expectations each theory would lead to. Part of the argument had
to do with the fact that the common design argument made no
necessary predictions about the patterns we see, but that common
ancestry did: for example, the amount of diversity in a given
family (say the cat family) and their biographical distribution
and the degree of diversity over time. Part of the argument
related to the fruitfulness of a theory in provoking additional
questions or additional research".
The predictions made drawing on the evolutionary tree analogy are
not successful - yet these have dominated thinking on these
issues over the past century. What are the "necessary
predictions" of common ancestry - and if they are not based on
the tree analogy, on what are they based?
The "cat family" example is not going to help here - for I
suspect that "common descent" below the Family level is a common
perspective of evolutionists and ID advocates. The latter are
likely to see the cat family, along with other families, as
Basic Types - with members related by interbreeding and
hybridisation and best understood as descendants of an ancestral
population. The real differences between evolutionary theory and
ID are to be found in their treatment of the
order/class/phylum/kingdom levels of classification. Hence
Kurt's repeated reference to "major groups".
Best wishes,
*** From David J. Tyler, CDT Department, Hollings Faculty,
Manchester Metropolitan University, UK.
Telephone: 0161-247-2636 ***