Goddy (my creationist alter-ego) is back!
One of the key evidences presented for common descent is the twin-nested heirarchy. That is, the hierarchies created from both the morphological evidence and the genetic evidence are correlated far more than would be expected by chance.
But what they (the evilutionists) don't tell you is that similarities are not evidence of common descent. They can also be indicators of common design.
Seeing as the DNA provides the instructions for building the organism, one should not be surprised that the two trees match up fairly well. Just as one would not be surprised that smaller cars would have smaller engines, we should not be surprised that organisms that look like people have genes similar to those of people.
Because these criteria used to create the two trees are not independent of one another, a correlation between the two offers no evidence for evolution or common descent.
In addition, if common design of phenotypes between kinds is valid, then so is common design between genotypes. While it is true that the genetic code is redundant and there is a lot of plasticity available in the amino acid sequence of proteins (e.g. conservative mutations), it doesn't follow that the genotype should vary more than it does. The designer clearly would have known about mutations, and so if one genome is good (i.e. sequence is arranged in such a way that it minimises information loss via evolution) for the dog kind, a very similar genome would be good for the cat kind too.
So, the twin-nested hierarchy doesn't disprove special creation at all, does it?
™ Version 4.2