A few months ago, Nicholas Matzke and Steve Jones were discussing
lizards and birds. I broke into the discussion, and Steve responded to
me thus:
LH>I've got a question for you, Steve. In your discussion with
>Nicholas Matzke regarding birds, dinos, and lizards, you seemed to
>come to agreement on at least this point: There are a number of
>late dino species with a few "bird" characteristics, and there are a
>number of early birds with many "dino" chacteristics; however, these
>(known) species do NOT clearly form an ancestral sequence. Is that
>accurate?
SJ>You are right re "a number of late dino species with a few `bird'
>characteristics" but not about "a number of early birds with many
>`dino'. AFAIK we only discussed *one* bird species Archaeopteryx. I
>am not sure if other early birds have "dino" features, or if they do,
>whether we disussed them. But I do concede that Archaeopteryx has
>some "many `dino' chacteristics".
LH>I'm guessing that you would argue that some of the changes
>necessary to go from dinos to birds (feathers, beaks, hips,
>breastbones, etc.) are non-trivial (mutationally), and would
>require "supernatural intervention at strategic points." Is that
>accurate?
SJ>No. I would need to consider each feature on its merits. It may be
>that "beaks" are easy to develop by an extension of the palette and I
>note that octopi, dinosaurs, platypi, and of course birds all
>developed beaks. I am interested in the *first appearance* of a
>feature, as this represents the first expression of a new
>"sub-routine" in the genetic code. So if "feathers" first appeared
>in Archaeopteryx, then that is where I would assume (not "require")
>"supernatural intervention" at strategic points." If it is later
>found that an earlier reptile had a feather, then I would assume that
>is where the potential "supernatural intervention" occurred in a
>recoding of the genetic code:
LH>Now here's the question: Suppose several late dino and several
>early bird species have a certain "bird" characteristic (e.g.
>beaks), but these species do not form an ancestral chain, would this
>require God to perform the same supernatural intervention at several
>different strategic points?
SJ>"Essentia non sunt multipicanda praeter necessitatem" (William of
>Occam)! :-) I would assume that only *one* "supernatural
>intervention" would be needed at *one* "strategic point" for the
>first appearance each new feature. One recoded, the code could
>remain dormant in the genome until needed again.
>BTW, I assume that birds and *reptiles* do "form an ancestral chain".
>I do not necessarily assume that birds and *dinosdaurs* "form an
>ancestral chain". I certainly do not believe that late dinosouars
>like Ornithomimus which developed a beak throws any light on the
>origin of birds.
An excellent answer from Steve. Now let's carry it further.
What about bats' wings? Their common ancestor with other winged
creatures goes back *long* before bats' wings first appeared.
What about the squid eye and the vertebrate eye? Both are complex, but
their common ancestor goes back a very long ways --- unless I'm
mistaken, well before the appearance of any complex eyes. In fact, I
believe that the fossil record suggests that complex eyes arose
"independently" considerably more than just twice.
Suppose we have a complex biological feature which we believe probably
required supernatural intervention. Now suppose this feature is found
in multiple groups whose common ancesters go back well before the first
appearance of that feature? Should we hypothesize multiple instances of
supernatural intervention to achieve similar features? Does this seem
less "elegant" than a single intervention? Should we hypothesize a
single intervention with a very long dormancy? Or would this pattern
suggest to you that, perhaps, that *particular* feature probably arose
through natural mechanisms? If so, why?
(This isn't directed specifically at Steve. I'd like to see several
people on this group wrestle with this question.)
Loren Haarsma