One of the main arguments to support evolution appeals to shared non-functional structures between organisms. Since design entails design for function, shared non-functional structures would suggest common ancestry in the absence of common design. But how can we tell whether something is truly non-functional? Here are some insights from a colleague that address this point:
As a programmer, sometimes I spend a lot of time designing error-detection and/or error-correction algorithms (especially for dealing with user input). Some of these functions may never, ever be used in a real-life situation. There are also various subroutines and functions that provide either exotic or minor capabilities that, likewise, maybe be used very seldom if at all. But they are there for a reason. Good programming practice requires considerable extra design and implementation of features that may only rarely, if ever, be used.
If someone were to cut out and eliminate these sections of code, repairing what’s left so that the program still functions, the program may work perfectly well for just about all situations. But there are some situations that, without the snipped code, would create havoc if the program tried to call on a function that was no longer there or that was replaced by some different function that tried to take its place. (Ask yourself what percent of the functionality of your spreadsheet or word processor program you use, and then ask if you would even notice if some of the lesser-known functionality were removed.)
I think biological life is like that. It seems to me that if some DNA code can be successfully removed with no apparent effects, one possibility is that the removed portion is rarely used, or the impact of it not being there has effects that are masked or otherwise hidden.
Perhaps redundancy is what was removed, meaning the organism will now not be quite as robust in all situations as before. I can give a kidney to someone else and suffer no ill effect whatsoever… until my remaining kidney fails and cannot be helped by the redundant one that I gave up (which situation may never, ever really occur due to my general good health).
P.S. Being able to snip something with no apparent ill effect may in fact provide support for ID by showing that the system was so well engineered that it could automatically adjust to a certain degree, and in most cases completely (apparently). It would be interesting to see some ID research into some of the evo cases that are being used to support the various flavors of junk DNA, to see what REALLY happens long term with the new variety now missing something snipped.