In a message dated 11/17/1999 you wrote:
<< Johnson's claim that macro-evolution has no scientific evidence to support
it is simply false. >>
We may have a problem of definitions here. If you consider _change over
time_ evidence for macro-evolution, then you are right. But I doubt if you
use "change over time" as your definition of macroevolution, do you?
If, however, you consider_descent with modification from a common ancestor_
as evidence for macroevolution, you will have some cogent disagreements. In
a recent paper, Malcolm Gordon claims that common ancestry is well supported
"from populations to the levels of genera and families" but even there he
adds, it is "apparent there are no single, universal scenarios, even at these
levels." He continues, "The least convincing applications of this view
[monophyly or common descent] involve the macro-scale of evolutionary
differentiation, the categories (kingdoms, phyla classes.) ("The concept of
Monophyly: A Speculative Essay" _Biology and Philosophy_ 14 (1999),
331-348.). In short, common descent has some evidentiary support at lower
taxonomic levels but is not supported by evidence at the higher taxonomic
levels, i.e., macroevolution.
Thirdly, if you consider the concept of _natural selection_ as the heart of
the Darwinian theory, as I do, then you will have many disagreements. The
oldest one is Mivart's objection (called Mivart's Dilemma) stated as,
"Natural selection is incompetent to account for incipient stages of useful
structures." Mivart leveled this objection to Darwin's theory of natural
selection in his book published in 1871. Stephen J. Gould had this to say
about "Mivart's Dilemma":
"Mivart awarded this criticism a separate chapter in his book, right after
the introduction. He also gave it a name, remembered ever since. He called it
"The Incompetency of 'Natural Selection' to account for the Incipient Stages
of Useful Structures." If this phrase sounds like a mouthful, consider the
easy translation: we can readily understand how complex and fully developed
structures work and owe their maintenance and preservation to natural
selection---a wing, an eye, the resemblance of a bittern to a branch or of an
insect to a stick or dead leaf. But how do you get from nothing to such an
elaborate something if evolution must proceed through a long sequence of
intermediate stages, each favored by natural selection? You can't fly with 2%
of a wing or gain much protection from an iota's similarity with a
potentially concealing piece of vegetation. How, in other words, can natural
selection explain these incipient stages of structures that can only be used
(as we now observe them) in much more elaborated form?"
Gould goes on to point out that among the difficulties of Darwinian theory
"one point stands high above the rest: the dilemma of incipient stages.
Mivart identified this problem as primary _and it remains so today_." (My
emphasis.) (Gould, S. J. (1985) "Not Necessarily a Wing" _Natural History_,
October, pp. 12, 13).
The problem for macroevolutionists is to employ natural selection to account
for "incipient structures", for example, between the mammalian land ancestor
to the "useful structures" of modern blue whales.
If Mivart is right, as Gould says he is, then Johnson is on target in
claiming that scientific evidence does not support macroevolution.
However, I am open to evidence that confirms macroevolution by natural
selection if you have any that I may not be aware of.
Thanks for your comments.