kuresu writes:
The only difference between Great Danes and Chihuahaua are which genes are expressed.
I don't think this is strictly true. Recent studies into the dog genome have found that the purebred lineages are genetically distinct from each other to a remarkable degree - with insertions, deletions, and sundry mutations accumulating easily in the isolated, inbred populations. The genetic differentiation between some dog breeds were found to be much greater than between isolated human populations on different continents, which is remarkable considering that most breeds have been created in the last 400 years or so. See
this Parker et al. (2004) article in
Science (link gets you the abstract, full text by subscription only - or see
this NCBI article which talks about it).
Some people argue (and I'm inclined to agree) that Chihuahuas and great danes are anatomically incompatible enough that they would be reproductively isolated as "wild" populations, and could be thought of as different species.
More directly to the topic, the definition of "macroevolution" has been a source of much goalpost-shifting from the creationist side. Since speciation has been undeniably observed both in the lab and in the wild, the more experienced creationists no longer consider "mere speciation" to qualify as a macroevolutionary change, which many insist is somehow impossible. I say this to help explain Faith's reaction to your very fine OP.
This message has been edited by Belfry, 03-25-2006 07:13 PM