In article <1991Nov4.232911.10631 at unixg.ubc.ca> schultz at unixg.ubc.ca (Stewart Schultz) writes:
>In article <1991Nov3.135246.1856 at ac.dal.ca> arlin at ac.dal.ca writes:
>Another aspect is that one might agree that genetic changes are
>overwhelmingly important, and still prefer to continue to label
>"evolution" those historically-defined cases that don't conform to the
>new definition. A desire to hold onto some historical or cultural or
>personal concept of evolution might, for all I know, prompt one to
>assert that a migration barrier is "evolution" because it causes
>reproductive isolation, even though one disputes none of the facts.
I thoroughly agree that genetic changes are *quite* important (most important
in the process). I can't fault that from what I have learned. My point is
that it is not necessary to refer to the mechanics of biological evolution in
it's 'definition'. How do we define 'living'? Does it have to do with sexual
or asexual reproduction? gametes? DNA? RNA?
>If we want our definitions to reflect our knowledge about mechanism,
>then causation is precisely what we should be talking about.
Our definition can take into account our knowledge about the system without
explicitly describing the system.
>It [the genetic definition] started out as a mechanistic hypothesis. The
>hypothesis is now so well-supported that it's become part of the definition.
Do you think so? Maybe. Does that mean that the definition and concept of
evolution will change when we discover a non-genetic living system? :-) I
know none exists that we know of, but we *will* find one.
>>Some paleontologists spend their entire lives studying evolution
>>without ever seeing a gene. ...These sequential transformations are
>>evolution, as we would all agree, but they are non-evolution by the genetic
>>Not necessarily. The weight of biological knowledge overwhelmingly
>favors the hypothesis that these transformations are genetically-based.
>One can define evolution as genetically-based change (from genotype to
>phenotype) and then decide whether any specific case conforms to it on
>the weight of evidence that the change is genetic. The weight of
>evidence is of course a continuum, and any two people might disagree
>where to draw the line, but in this case there's certainly a consensus.
Yes, again, you are correct in that the weight of our knowledge is in
overwhelming support of genetically-based changes, but I don't think that
paleontologists can explain all of the changes through genetic forces. There
are too many gaps in the fossil record. Still, the paleontologists describe
the changes from a phenotypic viewpoint, not genotypic and describe the
changes in relation to environmental factors and factors unknown. If they can
boil all of their changes to a phenotypic relationship, can we not also?
>The problem I think is that your opponents have different interests, and
>are having trouble understanding why all the brouhaha about the
>inconsequential fact that words' meanings vary by context, especially
>when the forum is a molecular biology newsgroup, and especially when
>we all seem to agree on the biology.
Biology is the central focus here. I did not try to take away from that in my
original posting. What I tried to do is broaden our concepts and ideas to
take into account data that could exist, but has not been found. Evolution is
such a broad concept that we need to create a meaning for it that is just as
broad. Vague, yes, but if we limit our ideas to what we know, and only what
we know, then we are limiting ourselves to our island. Look beyond our book
of knowledge and seek to add upon it.
Howard Hughes Medical Institute
taub at hmivax.humgen.upenn.edu