Current Biology Articles

Saturday, February 18, 2006

A Brief Look At Evolution

In a world dominated by religious dogma, where people turned to the Church both moral guidance and rational inquiries, two Englishmen offered a theory that challenged the old ways and unified the study of biology. Though history has credited Charles Darwin as the source of both natural selection and evolution, his lesser known colleague, Alfred Russel Wallace (A.R Wallace) had independently arrived at the conclusion. The experiences that formulated both versions of evolution were independent in time and location, illustrating that the phenomena was not unique to any one temporal or geographic location.
The concept of natural selection (as understood today) began with the HMS Beagle, a 235 tonne brig sloop, on which Charles Darwin travelled for five years. Though the ship was not commissioned to radically alter the face of biology, it inevitably helped its now famous passenger to do just that. Joining Captain Robert FitzRoy as an unpaid gentlemen, Charles Darwin looked forward to the opportunity to pursue his love for geology in South America. During the five year journey, Darwin had the opportunity to visit a group of small islands off the coast of present day Ecuador called the Galapagos. Darwin, a budding naturalist, spent a great deal of time collecting samples for later study and taking meticulous notes on rock formations and geological trends. As an after thought he embellished in the crews custom of collecting various species of birds from the locations visited. This tradition would set Darwin on the road to discover natural selection.
Though the birds played little role in his writings subsequent to his voyage, they ultimately gave him a reference to which he could ground his theory of natural selection. Darwin eventually returned to the birds after John Gould, an ornithologist, revealed that what Darwin thought were a series of different species of birds were in fact, all varying species of Finch. Intrigued, he began to pore over his notes quickly discovering, or re-discovering, that each species of finch had a distinctive bill, unique to a particular food source that was abundant to the island it was obtained.
Reading the ideas of economist Thomas Malthus, Darwin began to formulate the foundations for evolution. Malthus argued that a human population growing unchecked would double every 25 years. Because no environment can sustain infinite growth, there was intense competition for the finite resources available. Building on Mathuses idea, Darwin was able to apply the concept of competition for finite resources to the observations made during his journey to the Galapagos.
Variation between individuals of a species exists when combined with limited resources leads to competition. Darwin theorized that if the preceding statement was true, that species with advantageous variations would more likely survive then those without. This idea would explain the variation in the bills of finches he saw across the Galapagos, and explain why each bill was specialized to a specific resource abundant in the area that species of finch was found. Darwin coined the term natural selection to describe the process by which only favorable variations survive.
Though Darwin's roots as a geologist and his study of Charles Lyells, Principles of Geology , planted the seed for belief that great changes were the outcome of gradual processes over huge periods of time, Darwin did not apply this idea to biology until his study of fossils.
In 1837 Darwin began making detailed notes of evolution. Studying homologous structures, vestigial organs and embryological development of living species gave him ample evidence that evolution was occurring. Once natural selection became the avenue for explaining why evolution occurred, Darwin had amassed a huge amount of evidence for his theory. His facts eventually took the form of a 230 page essay written over two years, titled The Origin of Species.
Though he arrived at the same conclusion as Charles Darwin, A.R Wallace did so at a later date, taking a different route. Unlike his famous counterpart, Wallace was not interested in geology or rock formations; his goal was to solve the riddle of the origin of species. Like Darwin, Wallace chose South America as his destination to find an answer to the riddle. He found both evidence and bad luck. Concluding his voyage two years later due to an illness, A.R. Wallace decided to return to England and begin cataloging the large collection he had amassed. On his voyage home his ship caught fire and sank, taking with it a substantial portion of his samples. Determined not to let a little bad luck inhibit his thirst for knowledge, Wallace left for Indonesia two years later. It was during the eight years A.R. Wallace spent in Indonesia where he came up with his theory of speciation via survival of the fittest.
Unlike Darwin, Wallace did not study finches to formulate his theory, rather, Wallace observed a slew of organisms including the Rhacophorus Nigropalmatus, or the flying frog. Like Darwin, Wallace observed how geographic separation seemed to cause speciation amongst similar individuals. He too eventually connected these observations back to Thomas Malthus, eventually authoring a mechanism to how such change occurred. He called what Darwin referred to as natural selection, "survival of the fittest". The "survival of the fittest" concept used by Wallace was similar to Darwin's but not identical. Both agreed that some sort of selection occurred, but while Wallace described it as a natural phenomena, Darwin used selective breeding as a means to explain and understand the mechanism.
In essence, A.R Wallace arrived at the same conclusions that Darwin had some twenty years before. When he sent Darwin an early manuscript of his findings, Darwin realized that he could no longer hold back his results. Darwin himself described Wallace’s manuscript as an excellent summary of his original findings. After discussing the awkward situation with fellow scientists, Darwin published his paper and gave special mention to A.R Wallace and his work. Though Darwin received credit for the work they both arrived at the same conclusions. This final destination of sorts laid the foundation for future generations to regard the "Theory of Evolution" as more than just theory, but fact.
The affect of the publication was immediate, yet both viewed it in different contexts. Being a devout Christian, Darwin did not see evolution as contradictory to the world view as according to the Bible. He credited God for evolution and its mechanism, natural selection implying God may have created life, but natural selection is the mechanism for which life evolved. Wallace on the other hand horrified Darwin with his turn to "spiritualism".
The debate over the social and cultural implications was immediate. Evolution and natural selection were deemed heresy by the church and condemned as unchristian beliefs. Though scientists had a better understanding of what Darwin and Wallace were trying to convey, the general public were manipulated into thinking evolution was a theory of how they were a monkeys uncle. The misinformation and misinterpretation of exactly what evolution theorizes continues to this day. The most recent incarnation of the debate comes in the form of evolution versus Intelligent Design.
The debate is based on a core misunderstanding of not only what the theory of evolution expresses, but also the definition of a theory. A theory is a systematic and formalized expression of all previous observations made that is predictive, logical, testable and has never been falsified. Evolution is a scientific theory because it meets these criteria. Though Intelligent Design and alternative explanations offer critiques of evolution, they do not propose testable, predictive alternatives. Critiques do not qualify as scientific theories, yet many mask themselves as such.
Intelligent design for example offers two main critiques of evolution; the concept of specified complexity (also known as the "Watchmaker Hypothesis") and the Fine Tuned Universe argument. The prior makes the following claim; if a person is walking across a beach and comes across a pebble, they think nothing of it believing that it has been there by chance. If however, that person comes across a Rolex watch, it is obvious that someone must have placed it there. The minute intricacies of the watch leads one to the obvious conclusion that it must have been designed. Similarly, the minute intricacies of the human cell leads one to the obvious conclusion that a greater intelligence had a hand in its existence.
This argument works only in the narrowest of context. When taken further, the watchmaker argument poses a significant philosophical problem. If the watch had a watchmaker, who designed the watchmaker? Intelligent Design advocates offer the idea of an "uncaused causer", or a God like figure to solve this problem. This in itself is a contradiction to the original argument that complexity requires design. In essence, we begin reasoning in circles.
The Fine Tuned Universe is another attempt at a critique of evolution. The argument states that the emergence of life as we know it is dependent on variables so finely tuned that it must have been designed. Proponents of Darwinian Evolution dismiss this argument as one based on ignorance and lack of imagination. If variables including the charge of an electron were slightly different, life as we know it may not exist - but that does not mean life will not exist at all. More than likely, if given enough time life would exist, just in a different form. Bacteria living in thermal vents offer evidence to support proponents of Darwinian Evolution. Rather than using carbon as the building block of life, these bacteria evolved using sulfur as their major organic component.
? It is blatantly clear that critiques of Evolution are religiously motivated and based on misinterpretation of what evolution claims. It should be noted that evolution makes no claim of the existence of a "designer", rather evolution offers us a vehicle to explain the changes that have led to the variety of species seen today. Though both Darwin and Wallace may not have known it at the time, their research has led to one of the most controversial theories in science as well as one that has unified the study of biology.
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