Skeptics often argue for evolution and against creation by pointing to "bad designs" in nature. They say that if an all-knowing, all-powerful creator made life, these "inferior" or even "leftover" features would not exist. However, a closer study of the frequently used examples of bad designs reveals a different picture. They typically fall into one of three categories predicted by RTB's biblical creation model:

1. Unappreciated good designs. These are revealed as good by further and closer investigation. Examples include the inverted retina in vertebrate eyes and the giant panda’s thumb.
2. Intentional sub-optimization.  In these cases, one or more aspects of the organism or system is not optimized so that the whole system or organism works properly. The 30% inefficiency in protein synthesis provides an example.
3. Decay from optimal. An initially well-designed system decays due to the operation of the laws of physics. Deviants of the universal genetic codes illustrates this process.  

Any example of a so-called bad design in nature deserves deeper study to see if it fits into one of these three categories.