Wednesday, February 11, 2009

On the Celebration of Charles Darwin's 200th Birthday

Every February 12th, on the eve of Charles Darwin's birthday, those of us who have felt the impact that the theory of natural selection has on science and our understanding of the natural environment celebrate his intellectual rigor, scientific accomplishments, and outstanding character (please see the previous posts from the last two years here and here). We do not deify him, nor do we treat him as the exalted savior of mankind. We see him as an exceptionally profound human being who was able to methodically and critically analyze the data present to help us understand the natural processes that allowed us as a species to exist. Up to Darwin's Victorian times, many had already contemplated the possible connection between life forms, known then as the "transmutation" of species. As Western culture evolved, the idea that each creature was created in its present form, known as essentialism, had taken precedence. Some, such as the French naturalist Jean-Baptiste Lamarck, had embraced the notion of evolution, even though his proposed mechanism for the inheritance of acquired characteristics (basically, an example of his theory was that giraffes had long necks because their ancestors constantly stretched it trying to reach higher and higher branches, and this was passed down to their children) was falsified by Darwin. To understand Charles Darwin's seminal publication, "On the origin of Species", one must embrace the intellectual leap required in his day. The fossil record in the late mid to late 19th century was very sparse, the idea of continental drift was 75 years away, the understanding of embryology and developmental biology was extremely limited, and the idea of heritable units of DNA we now call genes completely unknown. In some alternate universe, the theory of Natural Selection would have taken much longer to develop. There were also severe impediments to accepting this theory, such as the age of the Earth (at this point estimated scientifically to about 100 million years, which Darwin knew was not enough time for the complexity of life to have evolved). Yet, after 150 years of publication, his theory still stands the test of time. His revolutionary idea has proven to be so rigorous, that it has stood up to countless new discoveries, and fields of biology that would have utterly shocked Darwin himself. We have come to the point where we now know that every human on Earth, every single functioning aspect that defines us, that we use as the human avatar, is found in only 20,000 genes. That's half of the genes found in rice, and yet, as hard as it is to be accepted by some people, there is no evidence that shows evolution to be wrong. In fact, this can be expanded into stating that with all the evidence at our disposal, evolution through natural selection has proven itself to be as near a certainty as science allows. There is no question that we, as human beings, are linked to all the species that exist and have existed on the Earth. Some of these species have evolved with us, since we've branched form our last common ancestor (concestor) with Chimpanzees. Other's have long since vanished, leaving their traces in the geological record. Their whispers however, occasionally echo through the fossil discoveries, some of them so ground breaking, that they almost instantaneously revolutionize our understanding of the links between early branches of species. With each fossil discovery, it seems that another piece of the puzzle is put together, giving us a picture that is so awe inspiring, that people hundreds of years in the future will look upon our current era as one of the golden ages (especially in genomic and molecular biology). Darwin would surely have been envious of our extensive capabilities in linking the fossil record with our tools of molecular phylogenetics (using certain segments of our DNA to determine an approximate date that a species split).

With all the vile, and irrational criticism directed against the theory of Natural Selection, it must be stated that evolution is a fact, no less true than gravity, thermodynamics, nuclear force, human language, etc. Charles Darwin's greatest contribution to evolution was uncovering the mechanism for it. The mechanism that results in the evolution of species is what he called Natural Selection. He uses this term to contrast the artificial selection that humans have used to help domesticate the natural world around us. He often referenced pigeons, because their shorter life-span compared to ours, and their reproductive fecundity allows a pigeon fancier/breeder to understand the ever-shifting role that selection plays in their external appearance. For example, if a breeder found a pigeon with a novel feature, such as feathery tufts that extended a few millimeters onto the leg, he may choose to continuously breed and cross-breed pigeons of similar appearance until one that has feathery tufts that extend all the way down to the lower legs. He can do this, not only within his lifetime, but within a few years, and thus, relate to the role that selection plays. Likewise, most of the existing breeds of dogs that are represented today have, for the most part, appeared in only the last 200 years, through artificial selection. All the agriculture that we have, has been modified from plants that were collected in the wild. The appearance of wild grapes or strawberries is quite different from the cultivated varieties. Anyone who has ever gathered wild strawberries can attest to their small size, whereas there are artificially selected varieties that are nearly as large as one's hand. There is no controversy when it comes to artificial selection because for the most part, these processes occur within a comprehensible time frame. Yet, the controversy over Natural Selection results because of its implication for the non-existence of God, or a prime directional force. Some people are so clouded with the belief of the existence of a meddling deity, that they're willing to reject a mountain of evidence against it. Since Darwin's time, we have come to realize that natural processes account for all the diversity we see in life today. Before Newton's discovery of the Law of gravity, it was thought by some that God (or insert your chosen deity) kept everything somehow tethered to the Earth. Before the discovery of the Periodic Table of Elements, it was thought by some that all the elements on Earth were composed of a few primary ones, or infused with the essence of something that was created by a creator. Now that we have natural processes to explain physics, and chemistry, Darwin came by, along with Alfred Russel Wallace, to help biology into its rightful place. The concept of natural selection has been the hardest to accept partly because anthropocentric views continue to dominate human thinking. We believe that somehow, we are different from all the other animals. That if we accept that human beings are a complete result of natural processes, with no input from a supernatural entity, we somehow do a disservice to our species. Basically, it's our egos that convince us that we are something special in the eyes of an imaginary entity that we create to feel comfortable in a universe that is apathetic to our needs. The ultimate implication that Darwin's theory of Natural Selection has, outside the sphere of since, is the continued lessening of the role that supernatural entities we create with our imaginations have on life. Philosophically, the eventuality is to accept that the natural processes that govern and dictate the universe are enough to explain everything around us. It is this fear that has resulted in so much unnecessary controversy.

One of Darwin's great weaknesses was the lack of an agent that dictated the heritable changes that are passed on from one generation to the next. Having explained natural selection as the mechanism for evolution, an agent is needed that leads to these heritable changes. In other words, what did mutation act upon so that changes occurred in speciation? Other questions Darwin asked was how did species from vastly separate continents have a common origin? If humans descended from apes, where is all the fossil evidence for it? How many species die and are fossilized in conditions to help preserve them? How does speciation occur when isolation is not involved? These questions were not enough to deter Darwin, but did result in his hesitation in publishing his work for nearly two decades. The impetus for Darwin's eventual publication was Alfred Russel Wallace, another great British naturalist, who had concurrently also discovered Natural Selection as the mechanism for evolution. Although Darwin's insights had come before Wallace, having taken two decades to thoroughly analyze all the collected specimens and attempt at correlating it with other fields, Wallace was ready to publish his data. He further felt that because he lacked the notion of heritable characteristics, which eventually was discovered to be genes, in the form of DNA, his work could become prey to indefensible criticism. Being a considerate researcher, Darwin agreed to publish his work along side Wallace's, and together, they unequivocally established evolution through natural selection as a theory of nature. What had allowed Wallace to publish his findings so quickly was that he was already a supporter of the transmutation of species before his expeditions to the Brazilian Amazon and the Malay Archipelago. What Darwin had observed in the radiation of Galapagos finches, Wallace had observed in the various closely related butterfly species in what's now Malaysia. Darwin needed an extra leap, in which he would have to independently discover the transmutation of species through his own extensive field observations. Eventually, with both fathers of evolutionary biology in agreement, other scientists where able to help further our understanding of biology.

Once James Watson and Francis Crick had discovered the agent for natural selection, molecular biology became to once again prove Charles Darwin correct. In Darwin's time, unbeknownst to him, Gregor Mendel had already explained the process of genetics through the inheritance of certain traits. It wasn't until after Darwin's death, in the early 20th century that Mendel's work was able to become widespread enough for biologists to form a solid link between genetics and evolution. Some of the eventual discoveries have befuddled scientists for generations. Even today, we are constantly reminded of how complex genetics and natural selection can be. We can't afford to become complacent and take our discoveries for granted. Of the various new discoveries which have truly altered the field of genetics and evolutionary biology within the last few generations are horizontal gene transfer, self organization (cellular), endosymbiosis, and epigenetics. I will probably discuss these new processes in another post. What's important however is that we now have irrefutable evidence for the validity of Darwin's theory of Evolution through Natural Selection. We know that mutations are caused by changes to the DNA, either directly to the sequence, or indirectly, effecting the signaling processes. Eventually, these changes are great enough for speciation to occur. Critics often use micro-evolution and macro-evolution in a pathetic attempt at generating artificial categories for species' changes. The truth is that evolutionary radiation is an incremental mutational process that may seem small in human time scales (as micro-evolution), but multiplied by a factor closer to geological scales, seems significant (macro-evolution). When selection is left to the environment, and not an intelligent agent, then the time required for observable and measurable changes often takes much longer than human time scales. This is when fossil evidence from the geological record is used to identify various species anatomically. If every single organism that ever lived on earth was preserved, and we had the fossil record complete, we wouldn't see different species. For example, if we were to follow modern human beings, back to the last common ancestor of us and chimpanzees, and then back to the earliest primates, we would see negligible changes between each generation. If we decided to skip back every 5,000 generations we would see small but noticeable changes. Skipping back every 50,000 generations, these changes would look even greater. Finally, if we skipped back every 5 million generations, the species would hardly look related to the one before (in fact, to do this, we would have to include the earliest tetrapods). Richard Dawkins calls this concept the "genomic library." Thus, observing evolution is often based on the perspective of time. We can't very well observe living changes every one thousand years, but we can observe the geological record and the fossils that have been left in the past. Knowing this, we can perhaps use the models developed through observing the past, to analyzing the possibilities of evolutionary changes into the future.

Embracing Darwin's concept of evolution through natural selection, and extending it to the modern synthesis we've developed in the various different fields of biology, allows us to philosophically examine the impact this theory has on our place in the world, and ultimately, in the universe. In the most basic ways, we are no different then all the other living organisms. Yet, what defines a species of organism is their unique adaptations that differentiate them from other ones. We, as human beings, have acquired many traits through lucky chance, that makes us unique, and does in some way separate us from other animals. We have advanced language, intelligence (most of us), problem solving ability, social cooperation, and even the possible ability to create artificial life. The process of natural selection, does not require a natural environment, but one that applies selective pressures from the environment. The changes that have occurred in species on Earth are non-directed, which again is controversial to some irrational people. They go through fits and loops in an attempt at explaining evolution as a non-random directed process. The evidence however, indicates that evolutionary changes in organisms are completely constrained by the environment, but not dictated by a hidden "directed" force. This is yet another futile attempt at injecting a supernatural conscience to something that does not in any way indicate it. Regardless of all the anti-evolutionary noise, we stand here, on the eve of Darwin's 200th birth day, with the technological sophistication that puts us well on the path towards creating life that was not a product of random changes in the natural world, but may still come to be a product of random changes within the algorithm of programs. Understanding evolution, especially our place in it, does not make us egotistical, but on the contrary, allows us to maintain some humility. We are after all, a product of our natural environment, and hold within us the power to truly change the world. We can either look at the world as our dominion (the Biblical belief) in which we have tyrannical reign over all organisms, or see ourselves as a vital part of the planet, with the unique ability to analyze our impact and address the problems that we cause. Further, we must strive to help our fellow human beings with more than just self-comforting, but ineffective prayers. We must indicate with our actions and deeds, our talents and our abilities, our desire to help further humanities and the planet's best interest. What Darwin has taught us is that we are but one of the many lucky inheritors of the ever changing world. How we choose to deal with this understanding is what ultimately defines our species.

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