Ah yes, once in a while I do overstate things and need to be brought back to
reality. However, I am not sure that in this case I would agree that I have
overstated. I will explain below.
> Surely that if just _some_ living species were the same in some
>previous epoch as they are now, that would just indicate that _those_ species
>had not evolved during the time since that epoch, but presumably other species
>could have. Of course, if _all_ species were the same at _all_ previous
epochs
>as they are today, then that would presumably be conclusive evidence against
>evolution (at least if one knew this to be a fact; if it were only known that
>all fossils could be interpreted as those of present species, that would not
>absolutely disprove evolution but still would be very strong evidence against
>it).
Remember that I used the term "earliest Precambrian". This is 3.8 billion
years ago, immediately after the period of massive bombardment of the earth
by meteors. Life could not have survived that bombardment (many of the
older lunar craters are of that age, I believe). Anyway, to find a full
blown multicellular, multiorganed, modern species in those rocks would mean
that it had to either be placed there by a spaceman or created by God. The
earliest evidence of the cell is at 3.4 billion years ago, 400 million years
later. Now, I would suggest an alteration of what I said. If the skeleton
of a house cat were found in rocks dated 3.8 billion years old and the first
cell was found in rocks dated 3.4 billion years old, (there being absolutely
no other cellular fossils for that 400 million years) this would rule
evolution out as a viable theory. Would it totally disprove it? Not to
some people but then we still have people who hold to geocentrism today.
>
> Maybe this shows that for a very well substantiated theory, it is hard
>to think of the plausible possibility of a small new piece of evidence coming
>in that would disprove the theory, but certainly there is the possibility of a
>large amount of new evidence coming in that might, and maybe a sufficient
small
>bit that would seem extremely implausible according to the present
>understanding. For example, if another self-reproducing life form were found
>on earth that were based on something radically different from DNA, although
>that would certainly not be evidence against the separate evolution of the DNA
>life forms and of that life form, it would presumably be evidence against the
>idea that both had evolved from a common ancestor that was as complex as life
>that requires DNA. (It might be hard to rule out a simple common ancestor at
>the chemical level, though even this might look highly implausible, unless one
>just says something akin to the unremarkable claim that protons, neutrons, and
>electrons are common ancestors for all forms of life, i.e., that all life is
>made of "the dust of the earth.")
>
I would agree with you here that a small piece of evidence would not
disprove evolution. But then contradictory evidence doesn't disprove a
theory until the evidence becomes overwhelming. In my senior physics lab
years ago, I measured the speed of light at something like 294,000 km/sec.
While this is a valid observation, one would not hold to a variable speed of
light theory based upon the poor measurement of a student physicist.
I would still claim that if EVERY life form had a unique genetic code, one
would be hard pressed to hold to a theory of common descent.
glenn
Foundation, Fall and Flood
http://www.isource.net/~grmorton/dmd.htm