Case Studies in Intelligent Design:The Detachable Ass

Opponents of Intelligent Design Theory are fond of pointing out instances of apparently-bad anatomical design and laughing, saying "what kind of intelligence would design something like that?"  I was reminded of this when reading the latest post at Pharyngula:

Derek Davis, director of the J. M. Dawson Institute of Church-State Studies at Baylor, said: "I teach at the largest Baptist university in the world. I'm a religious person. And my basic perspective is intelligent design doesn't belong in science class."

I. Am. Laughing. My. Ass. Off.

What kind of intelligent entity would design a Biologist with an ass that comes off when he laughs?  

At first glance, that seems to make no sense.  But actually there is a precedent: Eumeces fasciatus, the 5-lined Skink:

The brightly-colored tail is supposed to attract attention from potential predators, which then bite the tail instead of the head.  

As you can see, the tail comes off.  That frees the skink to scurry away to safety.  The Lord knows, many skinks have survived potentially-deadly attacks by having a detachable ass.  (I think that the color in the picture above is not really accurate; I've never actually seen a skink with a brightly-colored head.  That would sort of invalidate the argument about he coloration of the tail serving to attract the attention of predators.)  

Anyway, the point is, that it does make sense to have an ass that comes off.  Now all we have to explain is this: why it would come off while laughing?