The human eye stands as one of the outstanding examples of a complex biological mechanism that is either difficult or impossible to explain in purely evolutionary terms. The fundamental concept behind “irreducible complexity” is illustrated well with the eye-it doesn’t work unless all the major parts are there all at once.
Therefore, the eye represents one of those hills that evolutionary theory would like to take. Many are sure it can be explained by purely naturalistic processes (if that is the only interpretive model you have then by definition, everything is or will be explained by it) even if there is no robust theory at this time. Enter one of the oldest moves in the Darwinist playbook. If the chemical or biological pathway can’t be explained, then surely the physical approximation theory has to work. Something smaller and older looks like the latest evolutionary branch in the tree, so the two must be related.
This kind of move has been a major justification for the evolutionary model for a long time. We all remember the sketchs of human embryos and tadpoles whose purpose (which turned out to be deliberate hoaxes) was to make us all believe that becuase we all looked like tadpoles at one point, we are therefore related to them. That explaines why tall, skinny NBA centers are evolutionarily descended from Festivus poles.
This commentary, put out by the Intelligent Design movement, links to the latest incarnation of this visionary model. Don’t be taken in by the level of similarity (sub-cellular). The argument is the same: If they look alike, they must be related.