Might I suggest that you are going against your own advice in suggesting that we need to tackle the issue of similarity to help out creationist biology? Like the "lower level" theories of evolution, similarity appears to be here for good.....I'd almost hazard to say fact. So what if similarity backs up evolution? We should not be trying to disprove evolution, but we should be building our own models to support creation......focus on that will do more to crack nuts than any attempt to disprove the Theory of Evolution (just my humble opinion).Wow. Talk about using my own words against me! That's great food for thought, so let me see if I can come up with a decent answer:
I've long argued that there are basically five issues that creationists need to tackle: Design, evil, speciation, systematics, and biogeography. For example, when we think about identifying created kinds (systematics), we're basically looking at what is or isn't similar. Yes, I know that Frank Marsh (and other creationists) disputed that, since he was looking at what species could or couldn't hybridize, but that ability to hybridize correlates with outward similarity. So it's similarity.
Then there's natural evil. One way creationists have tried to tackle that is to compare pathogens to closely-related nonpathogens, to see what kind of changes might have made the pathogen. That's a similarity argument as well. Biogeography? Why are similar species so geographically close, and what does it mean when similar species are separated by dispersal barriers? Speciation? I've suggested studying that subject by comparing genomes of species in the same terrestrial baramin. There's that similarity again...
As for design, that term gets wrapped up in the sort of reductionistic design that characterizes the ID movement. But when I look at baramins, I see patterns of similarity. I see many baramins grouped together in categories like "bird," "mammal," etc. If baramins are truly separate creations, then that similarity must be the result of design. So what does it mean? Is it a revelation? Does it have the characteristics of language? Something we could actually decipher? That's a captivating idea.
So in my estimation, biological similarity undergirds most of creationist biology, just like it does evolutionary biology. I have perhaps mis-emphasized "answering evolution" as an justification for why we ought to study biological similarity. Please consider this post my correction of that error.
Feedback? Email me at toddcharleswood [at] gmail [dot] com.