No, of course there's no way to prove that natural selection &co are
responsible for common ancestry, or that Pluto really has an orbit, or
a multitude of other things. The approach scientific theories usually
take, though, is to figure that if the mechanisms we see now are sufficient
to explain history, and there is evidence that they were operational, then
that is the scientifically defensible theory.
But there is still a bit of vagueness in the definitions--that is, by
'microevolution' you seem to agree that natural selection is responsible
for the sorts of variations we can see happening now. This includes
speciation events, BTW. I agree that there are open questions surrounding
how natural selection could operate to drive common ancestry, and its
role in this process is under current discussion (as Al mentioned in another
post in this thread). That is, what are the developmental parameters
which constrain selection? Why is the rate of 'macroevolution' so low
in comparison to the rate of 'microevolution'? Where are sticking points
that make overall geologic-time evolution so slow? These sorts of questions
are very much relevant, and I think there is enough reason for people to
be cautious about attributing it all to natural selection. But common
ancestry (what is typically called 'evolution' popularly) is a fairly
different animal from these considerations, and is supported on different
grounds.
> Well, I don't know anything about Lamarck or somatic patterns. However,
> let me expand upon my point. How do you know whether or not a mutation is
> random, or pre-determined? How do you know if ANY event is random or
> pre-determined? Well, just about the only way is to see if there is a
> pattern to the event.
Lamarck said that acquired characteristics are inherited. That is, if
you are a carpenter and get callouses on your hands, your children will
be found to inherit the tendency to have callouses on their hands.
Nowadays, from what we know about inheritance, this seems to be safely
ruled out, precisely because mutations appear random, but a mutation to
encourage somatic patterns (acquired characteristics) would be *non*random.
This doesn't rule out other non-random influences of various sorts, though,
as Al mentioned in another post. Personally, I would be excited to see
evidence that this is so. It is just a bias, but I think we overemphasize
DNA at the expense of the surrounding environment of which it is a part.
> If there is a pattern to the event, it is a safe bet that it is
> pre-determined. However, it doesn't take long to see that life on our
> planet does not follow a pattern, at least, not one we can discern.
>
> So if there is no pattern to the event, is the event random? Maybe. But
> maybe not. I can't read Chinese; to me, it looks like random marks on a
> page. It might be a great Chinese novel, or it might be someone's laundry
> list; I can't tell. I can't discern the pattern.
>
> Whether or not the event is random is not academic to the evolutionist, it
> is of utmost importance. If the event is truly random, then you can
> easily say that evolution is a purely naturalistic process -- which
> evolutionists do say. But if the event is not random, if it is
> pre-determined somehow, then what are the determining factors?
I'm sure there are many evolutionists who would be happiest with mutation
solely as a random process, but I think the vast majority would be happiest
to know how it *really* works, even if it isn't how they expect. Why
would a non-random mutation be non-naturalistic, though? There are millions
of non-random processes that are purely naturalistic. What is the reason
for supposing this one wouldn't be?
> > No, common ancestry is assumed to be true, not because someone was
> > videotaping it, but because of many different lines of physical evidence,
> > one of the most important of which is the nested heirarchical patterns
> > found in the DNA of living things.
>
> Well, again, you're venturing into areas I know nothing about. However,
> common ancestry is not enough to prove macroevolution. Nested
> heirarchical patterns in DNA is not enough to prove macroevolution.
Perhaps by macroevolution you mean the idea that natural selection is
responsible for common ancestry. That's a frequent usage, I suppose, but
given that "real" biologists don't use the term, there isn't much anchor
to stick it on. Why don't we stick with the usually-accepted labels
of common ancestry and selectionism?
> Let me rephrase those bold statements: common ancestry and hierarchical
> DNA patterns ARE enough to prove macroevolution IF you assume the
> mechanisms are sufficient to bring these about. But the mechanisms are
> precisely what we want to prove! You can't prove that which you've
> already assumed. Thus, the tautology arguement.
Well, of course selectionists wish to show that natural selection is the
primary "creative" process whereby the variations expressed in the history
of common ancestry were consolidated into the form in which we see them,
but they don't assume (or rather, try not to assume) selection to do so.
(They are made fun of when they do as telling 'just-so stories'.)
Perhaps the confusion comes from using 'macroevolution' to mean two things:
the 'raw material' of common ancestry which selection is meant to (at
least partially) explain, and the process of explanation itself. This
would yield something like 'Evolution happens because of evolution' which
looks tautological until you realize that two different things are meant
by 'evolution' here: the evolutionary change of common ancestry and the
evolutionary mechanisms responsible.
> > Paleontological discoveries of the
> > time frames in which the various species existed, transitional fossils, and
> > so on are all supporting lines of evidence for this conclusion.
>
> Perhaps, but they are at best circumstantial evidence. I could conceive
> of a creationist theory that also accounted for not only the existence of
> these fossils (whether or not they are truly transitional is always open
> to debate), but for the absence of other fossils. So, where would that
> leave us?
It leaves us nowhere until you actually do.
> > (This
> > is nowadays, of course; Darwin reached the conclusion on much slimmer
> > grounds, but sufficient for he and his contemporaries to realize common
> > ancestry. In those days, it was considered impossible to notice the
> > "microevolution" of species, because it was thought to be too slow
> > a process.)
> >
> > The worry about 'fact' and 'theory' is usually a misnomer: any scientific
> > idea is 'theoretical' in the sense that further observations can overturn
> > or modify it. Some are so well grounded, though, that they serve further
> > investigations in the role of 'facts.'
> >
>
> Not "any" scientific idea, but EVERY scientific idea! But if that is
> true, why do scientists such as Gould speak of "the fact of evolution" as
> if no further observations could overturn it?
Because they're talking about common ancestry, which is the material with
which they work. That the Solar System actually exists, and is not painted
with a brush on some sky-roof every evening, is a theory astronomers have
which they would probably call a 'fact,' and which underpins their
investigations into what the solar system is like. Common ancestry is
the 'fact' which underpins modern evolutionary investigation into the
processes that drive evolution and the paths it has taken.
> The worry about 'fact' and 'theory' is a real problem, not just a semantic
> one. The concern is that treating evolution as a 'fact' leads scientists
> to make assumptions, and that taints their research. Not that assumptions
> aren't necessary, but you have to be willing to follow the findings of
> your research to their conclusion, wherever that might be. If you are
> already convinced that evolution is a 'fact' and simply must have
> occurred, you may be reluctant to follow your own research to its
> logical conclusion.
If you do not think that common ancestry is a fact, then modern evolutionary
theory cannot be of much interest to you, since it is attempting to explain
something which you don't believe exists. Your argument is with the
scientists of a century and a half ago. Just to save time, though, it is
probably fruitless to try and persuade biologists to join you in refighting
those battles. Just like astronomers still are not trying to convince
people that telescopes actually record real things when pointed at the
heavens, and are not instruments of evil, biologists are, for the most
part, uninterested in rehashing the settled arguments of the past.
The newest Creationist literature, it seems to me, is a great improvement
in that it is placed in this territory--Behe (by all accounts) thinks that
common ancestry is a fact as much as Gould, but has doubts that currently-
active evolutionary processes can explain it. This, to me, seems like
a much more interesting and potentially fruitful discussion than arguing
about moon dust, the second law of thermodynamics, and Archaeopteryx for
decades on end.
-Greg