Alan Turing is considered to be the father of modern computer science. An English mathematician, he made his mathematical debut during the second world war, when he discovered that German officers were either careless or lazy and had used the same cypher key in their infamous "Enigma" machine to code two different messages. The machine should be changed with every message you feed it but if you use the same key to encode two different messages, that is enough for a clever mathematician to guess the arrangement of gears within the machine, and therefore figure out exactly how the machine works so you can build your own to encrypt and decrypt any secret message.
But Alan Turing's most valuable contribution to the world was to create a mathematical description of the ideal computer, which we now call the "Universal Turing Machine". His work would inspire the American, and Manhattan Project designer, John Von Neuman, who actually constructed a working computer based on the mathematical design of Turing, for the purposes of performing bomb calculations. The computers we use today are actually based on the exact same design as Von Neuman's machine, except some ten or twenty orders of magnitude faster and smaller.
Turing's universal machine allowed for use to theorize about the limits of computation. In the early days, even before "transistor radios" became a household technological buzzword, much less the "167-million transistor Intel Pentium Dual Core", the mathematicians in Turing's crowd had discovered some of what was possible and impossible to compute. Other questions, for example the "P = NP" question, remain unanswered to this day. In so many words, the P = NP question has to do with whether or not some algorithms which solve very complex problems can be reduced to solve it in fewer steps. For an 'NP' algorithm which takes 100 steps to solve some problem be simplified to a more efficient 'P' algorithms that can solve the same problem in 10 steps? Answer that question and you will win numerous prestigious awards for mathematics.
Fast-forward 50 or 60 years, to present day Evolutionary Biology. A name like Craig Venter has the possibility of being the next "Alan Turing" for the future generation of computers. These futuristic computers will work not with transistors, but DNA -- that's right, Deoxyribonucleic acid. His institute is engaged in research which will take an ordinary cell and replace it's DNA so it will start acting differently. This process occurs naturally in a variety of micro-organisms, for example a bacteriophage that injects it's DNA into a bacteria to effectively hijack the bacteria cell to use it as a carrier. The difference is, we now have the ability to construct a DNA sequence so we can define the behavior of a cell, or an entire organism.
Of course, this technology is only in the beginnings, and it may be quite some time before we can engineer DNA to grow our own versions of an organism as complex as humans. But this is probably a good thing because that means it is equally difficult to engineer the perfect human-killing virus, like in that movie "12 Monkeys." This nascent technology is excellent fodder for science-fiction writers. Imagine a war of the future where our weapons are horrible diseases which infiltrate the water, food, and air supply of our enemies which we use to control their minds, and the only way we can defend ourselves from such attacks is to engineer a new human-like organism which is immune to the virus, then grow these new humans and copy our own brains into them so we can continue to survive with our will intact. Victory goes to those who are most unaffected by the will of their enemies; enemies who wish to take over your will and control you to achieve their own purposes.
I am reminded yet again that our cells are our very essence, and therefore our very essence is controlled by an unchanging genetic program. Even our own mind, which is the only thing that defines what we truly are, is subject to the unchanging genetic program. Our will, ourselves, what it means to be human, everything we know and everything we do is simply a complex process of pre-determined behavior. We are a complex construction built from countless iterations of extraordinarily simple, mechanical actions.
Now to me, this thought is not depressing, nor is it setting me into some existential crisis, rather it is a very amusing thought. Especially considering how many people in the world actually believe "free will" exists. But I am thinking bigger ideas than just "humans are complex machines." What if the entire universe is actually made of cells? Some kind of super-cells that have a simple behavior but iterated over vast expanses of time which result in ourselves existing and the universe we know. The idea is actually not new. Several philosophers have posited that the universe is actually a fractal, and it doesn't matter which dimension or which property you isolate and observe, it will always exhibit the same behavior. A human acts like a cell, which acts like an atom, which acts like a solar-system, which acts like a galaxy which acts like the whole universe, and perhaps anything that exists "outside" of the observable universe will behave the same way.
In that humorous science fiction book "The Hitchhiker's Guide to the Galaxy." An advanced alien civilization has already discovered the one and only answer to everything in the universe, which they discovered by running a vastly complex computer program. They discovered that the answer is 42, but were unable to understand the question which 42 answers, which is why they built an even bigger computer program. That complex program is the earth, and we humans are just one of the billions of complicated sub-programs that are behaving exactly according to our pre-determined instructions to develop this perfect question and help the aliens understand the universe.
Be this science fiction or a yet-undiscovered scientific fact, it is a very exciting prospect that perhaps any question can be answered by iterating a simple recursive pattern until the solution emerges. This gives new importance to those questions posed by Alan Turing, about whether or not a complex problem can be reduced to something more simple and efficient.