So arguments about a common ancestor rather a common designer seem to be less well founded.
<snipped to preserve sanity>
OK, I have about had it with this "common designer" argument. It is an absolutely appalling argument and we need to nip this thing in the bud. So now I will teach you why this claim is utter idiocy and works in exactly the opposite direction of what you, AiG, and all other creationists intend.
The common designer claim centers on the use of a given item or set of items and designs for a second unit as compared to a first unit. It is the use of the same 357 engine in two different Chevy cars. To understand why common design is such a bad proposition, you need to understand why Chevy (or any other industrial manufacturing firm) uses items or designs in multiple units.
Imagine two units being made by Chevy. One is a car, the other a pick-up truck. Each unit has a slightly different size and shape as well as slightly different performance requirements. Yet each is designed with the same engine (and many other parts/systems). Why? Why doesn't Chevy design two different engines so that each of these units will have the perfect engine for its size and requirements?
Chevy reuses the same engine in each of these units (and others as well) because Chevy is limited in design and production resources. Chevy does not have the money and resources to design and manufacture a unique set of parts and systems for each model it produces. If it did have these resources, it would make a complete set of unique parts for each model and there would be no commonalities.
And History bears this out. In the golden age of auto manufacturing in the 1950s and 1960s, American auto manufacturers had vastly less commonality than they do today. At that time, imports were low and profits were high so this could be done. But as competition increased and profits shrank, commonality became, well, more common.
So the reason common parts and designs are used in human manufacturing is because there is a limit on the resources both in design time and manufacturing capability. Common parts and designs are accepted not because they are the best, but because they are good enough. By definition, a commonality in parts or design is sub-optimal. There would be no such thing as common parts or designs if resources were unlimited. That bears repeating; commonality in parts and designs is sub-optimal.
So when creationists use the common designer excuse to explain why common designs are seen in nature, they are (probably unknowingly) stating that their god has limited resources. That he didn't have the time to design the perfect thing so he went with what he used on the previous animal. He used something sub-optimal. And this pretty much flies in the face of this whole universe in six days thing.
The common designer explanation actually supports evolution. Evolution cannot come up with something new and unique for every design, so it has to re-use/re-purpose what it has to start with.
The common designer explanation perfectly supports evolution and perfectly refutes creationism. So why do creationists use it? Because they don't know any better. Because they have not thought it through. And mostly because the evidence of "common design" in nature is so ubiquitous and so perfectly supports evolution that it screams for some sort of rebuttal if creationism is to survive at all. So the common design explanation is a desperate attempt to explain why nature is perfectly at odds with their claims. And the slightest bit of thought reveals the bankruptcy of their efforts.
So please, creationists, don't use this one any more. It obviously does not support your position. In fact, it derails it. Time to come up with something different.
And its "moot", not "mute". I hate it when people do that.
