One of the most pressing questions I've had in the past regarding life was how a cell knows what it is and how to act in the presence of others. We are, after all, beings made up of multiple cells that all work together to do amazing tasks. Though seemingly coordinated, our cells aren't really aware of themselves or others, but they certainly act like it. To the untrained mind, complex reactions like the immune system and orgasm seem like products of a cellular intelligence, but they're not. The question nagged me until I finally set about on a question to figure it out. The simple answer is "DNA," but that doesn't begin to explain the elegance with which cells interact with each other to form multicellular organisms and, eventually, us. The other key to the puzzle is "local rules," or, as Richard Dawkins explains, simple instructions on how to perform, actualized by genes, replicated within every instance of a cell, all working as if conducted by a leader. Asymmetrical cell division, which accounts for the varying types of cells, affects the available elements within a cell, causing differentiation. Mash it all together and life makes more and more sense.
An aside: There is no need to throw one's hands up and proclaim overwhelming complexity anymore. Nor is there room for cop-outs like claiming that all of this knowledge is merely theoretical. The recent breakthrough synthesis of a living bacteria cell from man-made DNA puts it all to rest. We know how life works and it certainly isn't god. The most remarkable point gleaned from this feat, in my opinion, is the triumph of science amidst all the doubt in its competence. It works, suckers. I've heard proponents of Intelligent Design actually claim that the synthetic DNA experiment actually reinforces their idea. Beyond saying they are idiotic, I would like to state that you cannot piggyback on the triumphs of the principles you flat out deny.
Once I understood that life works on a minuscule level, the rest seemed to fall into place. Natural selection can be reduced to a simple idea: which DNA molecules successfully replicate and which do not. The entirety of life is nothing more than a DNA replication engine. We are nothing but vessels for our DNA to replicate through. The first question to challenge this is, "Why would DNA go through all the trouble and energy of creating an entire living organism just to replicate itself when it could be a single cell that just divides itself?" A valid argument. It is true that it takes a significant amount of energy and resources to become us and then to find a mate and reproduce and that seems like such a waste when more efficient ways are available. Once again, there is a simple answer and there is a complicated answer.
Life is an arms race. Keeping in mind that natural selection is a passive result more than it is the agenda of nature (hint: nature has no agenda), life on Earth today is simply a reflection of "what worked." In the beginning, survival of DNA (More accurately, RNA. DNA developed later.) was as simple as a cell dividing to become another organism. All cells need energy, however, and over time, a few things happened. Some organisms became better at using energy than others, resulting in the monopolization of resources. This spelled out the demise of some strains of DNA, while others flourished and continued to slowly change over time. The ones that became better and better at monopolizing the resources won out. Eventually, different abilities evolved that affected how cells interact with each other and their environment. Some cells attacked other cells, so the ones to survive were the ones that were either fit to destroy or fit to survive. Some organisms developed new ways to take advantage of the energy around them, so their survival became independent of the survival of other organisms until, of course, they became food. Every new advancement changed the game and the rules for survival favored different and opposing traits.
Evolution: a giant game of one-upmanship. So, why go through all this trouble? Over the course of a few billion years, the arms race has veered so far off the course of simple cell reproduction, that our DNA now contains so much information about adaptive changes, enough to create us. Along the way, the adaptations have not been ideal (See: vagus nerve), but they have been enough.
Before I get too excited, I should return to the original point. Science is hard. It is complicated, convoluted, confusing and confounding. But it works. And if you go through the effort to understand how it works at even the smallest level, the rest works itself out. Understand DNA's role in a cell's creation and management. Understand the local rules of a cell as determined by its DNA. Understand the chemical reactions and why they happen. Understand life. You may say that this takes all of the passion out of existence, but that's not my problem. If life sucks without the idea that there's some magic, you can blame your parents for bringing you up with unrealistic expectations. As for me, I love the elegance of it all. The fact that I am nothing more than a bag of interacting molecules is rather cool. Know your true self and live it.
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