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Jurassic Park & Chimerae



>The point I was trying to make in the previous article was that the
>creatures formed, whatever they were, wouldn't be dinosaurs.

I understand that.  I stated as much, in the very first post, and in
the second.

>Even so, the
>monster might be interesting in and of itself, but would probably shed
>little to no light on dinosaurian biology.  There is a vast body of
>research on pleiotropy (sp?) and multigenic traits showing that the one
>gene - one character hypothesis is a great oversimplification.

We don't need such mapping, nor do I believe I suggested it.  However,
some traits require fewer genes than others, and physical traits are
easier to evaluate since the feedback can be obtained with a simple
X-ray, rather than months or years of study of bahavior.  But I must
disagree most strongly with the claim that it would shed little or no
light on dinosaurs: even _one_ functioning dinosaur gene would be a
useful object to study, even if it were only operational in a little
white mouse.  It is precisely that sort of chimerae that are used
every day in biological research.  Recall that special breed of mice
with human immune systems.

>Furthermore, from a phylogenetic standpoint, it would be more appropriate to
>use birds rather than mammals to grow a dinosaur.  Note that under the line
>of descent classification scheme, birds are members of Dinosauria anyway, so
>if you want to see what dino DNA in action, just take up ornithology.

:) Thanks, I'd figured that out.  But my point is alittle different:

1. Apatosaurs (to take one example) are large, land-dwelling herbivours.
   The closest analog alive today is the elephant.  Even if elephant genes
   are _not_ closely related to apatosaur DNA, they will be more likely to
   perform a similar function: a framework, if you will, to get apatosaur
   DNA into living action.  We could start with a hummingbird if we wanted
   to, but that would require a lot of work to make into a large land-dwelling
   herbivour, even if it _is_ phylogenetically a closer relative.  Even an
   ostrich, to take a slightly less ridiculous example, would be vastly
   further away.  The objective is to make a _living_ chimera, presumably
   on a budget.

2. DNA is DNA.  We can tell how old a particular sequence is, and if some
   sequence is old enough for a dinosaur to have had it, then there is a
   real possibility that sequence was actually _in_ a dinosaur.  It is
   possible, in theory, that we could reconstruct an apatosaur simply by
   finding all the critters still alive today, no matter what their direct
   relationship, that has pieces of that DNA, whether inherited directly
   from an apatosaur, or indirectly from a common ancestor.

>In any case, mammals have some 300 or more million years divergence from the
>sauropsid line, and so have acquired far too many traits to be useful in the
>scheme suggested.

How can you reach this conclusion so easily?  I figure to get DNA from where-
ever it can be found.  I expect the most useful bits in actual reconstruction
_will_ come from birds, for just the reasons you suggest, but I think it would
be too big a first step to take a bunch of birds apart and try to make an
apatosaur out of the DNA bits.  You _need_ chimerae as intermediate forms, to
see if you are the right track.

I stuck with the apatosaur for the above example, but I am not unmindful that
bird DNA would be a terrific place to start to reconstruct an archeopteryx.
Or even a small dromeosaur.

>  On the other hand, birds share in their genetic structure
>the common DNA heritage of the Dinosauria, Theropoda, Coelurosauria,
>Maniraptora, etc. (albeit expressed in a highly modified manner).

Like I say, I'll take it from whence I can get it.  But I doubt we can
assemble a dinosaur at one go.  Construction requires scaffolds.

But here's an interesting question.  Jurassic Park was just a plausible
hook for Crichton to hang another of his new-age anti-science stories on.
But suppose someone came up to you with a hefty check and said, "I wanna
see a live dinosaur.  I don't care about the cost or time, I wanna see it."

Just how would _you_ go about pulling them back from extinction???

And just what dinosaur would you try to recreate first???

Myself, I'd test the whole idea by grabbing all the mammoth DNA I could
get my hands on and go to work on some Indian elephants.  Not a dinosaur,
but it would prove the idea of taking a living animals and working it
toward the goal.  As each piece of mammoth DNA was inserted, the next
generation "elephant" would look a bit more like a mammoth, until it
_was_ a mammoth, for all intents and purposes.  Yet, each generation
would not be so different from the previous one that problem arise with,
for example, gestation or other biochemical factors.

'course, it might not work.  But the speculation is fun.  And, unlike
Jurassic Park, I think this _is_ a plausible way to make dinosaurs.
It might even be a plausible way to make most anything short of a
chlorine-breathing alien.

Larry Smith
larrys@alpha.zk3.dec.com