Tuesday, August 9, 2011

Homologous Structures

I love my iphone – it has got to be one of the most useful devices ever created.  Not only can you listen to music, but you can also watch movies, check email, surf the internet and of course play games.  I must admit that the App Store has become one of my guilty pleasures of late, and have been continually amazed at the ever burgeoning supply of available applications.  There is an incredibly diverse array of applications ranging from file storage programs to photo editors to the most unusual of games.  I have smiled on the inside playing some of these games thinking about the creative gifts that God has blessed some people with.  There is nothing that pleases me more than to encounter something that is truly original, and the App Store has provided me with plenty of those moments.

As unique and vastly different as all of those iphone applications are from one another, if we were to ‘look under the hood’ and compare the raw binary sequences that compose these programs – there would be a very high degree of sequence similarity!  In fact, there would be vast and repeating regions of identical sequences common to all of the programs.  Why should this be the case?  Each application after all represents a unique effort by an individual or team of individuals to turn an idea into a functional program.  Although the ideas of these individuals may have been inspired by previous applications, every programming effort must begin from scratch.  The answer to the mystery lies in the fact that similar programming languages are used by all the programmers.  Programmers don’t program using raw binary sequences, but instead use languages that have been built up from those sequences.  Even the simplest commands used by programmers represent a huge binary sequence that will be repeated every time that command is used.

When we compare the raw DNA sequences of living things to one another there is also an astonishing degree of sequence similarity common to all life.  Like computer programs, the level of similarity between sequences will depend in large part on the types of living things we are comparing.  Life that is outwardly similar structurally will most likely share a greater degree of common sequences.  In the same way, a word processing program will share more sequence similarity with another word processing program due to the nature of the application.  This is a natural consequence of the programming language used to create the applications.  When the end result is similar, it is necessary that there will be a greater degree of common commands used to achieve that end result.

The programming language of life is proteins; proteins determine the chemical environment of a cell which in turn triggers developmental changes.  DNA could be compared to the binary sequences in computers, and its primary function is to encode for proteins.  You could think of the proteins as representing ‘commands’ in the programming language of life, and hence many of these ‘commands’ are found in almost every living thing.  It is therefore not surprising that similar proteins can be found in bacteria, plants, animals and humans!  Of course like computer programs, the degree or percentage of similar commands will depend on the type of living thing that will result from the program.  For example, as different as every human being is from one another, our DNA sequences are all 99.9% identical!  When compared to a mouse, we are 70% identical.

If we were to collect all of the different App Store applications and compare their structural and sequence similarities, we could create an evolutionary tree from that information!  We could determine which application ‘gave rise’ to other applications based upon ‘homologous structures’ structurally and ‘genetically’!  Of course we all know that would be utter nonsense, because each application was created from the ground up by a designer.  Even though applications can be ‘tweaked’ to a certain degree, once created they are limited in the amount of change they are capable of.  Life is no different – God created life with the ability to adapt to changes in the environment to a certain degree, but the degree to which life can change once created is limited.