Monday, October 6, 2008
Mel's work on The Theory of Evolution
3:18:46 AM CDT
Hearing Double Dutch Bus - Frankie Smith
Mel's work on The Theory of Evolution
Since this will be our last discussion together, I'm going to admit to some of the feelings I have experienced while in this class. First, there's the ever popular, "I must love to argue just to argue", but more so lately, it's become the "I must be a freak of nature because I don't see things they way everyone else does".
I grew up Catholic, going to a Catholic school and learning history and science through the eyes of the Catholic Church. It's not a bad thing, it's not something I wouldn't want for my own children. Looking back, I realize that it was these younger years of my life that shaped and molded me into the person I am today, and by today's standards, I was quiet lucky to have the opportunity. What you must understand however, is that the opinion on the creation of earth and how humans came to inhabit the earth were not necessarily taught in the Catholic school. I wasn't even introduced to the idea of Dinosaurs until my parents moved and I had to attend a public school. Can you imagine how confusing these conflicting views were to me at that young age? Wonder if that's why I'm so easily confused now? LOL
The one thing I learned from all this is that there are certain theories and hypotheses that people subscribe to, and not everyone has the same subscription. I began to realize that what was best for me was to try to look at several views of a topic and devise my own opinion based on my beliefs and my own research into the subject.
With all that being said, I must confess that I don't agree with your views on natural selection, although I certainly respect and admire them.
First, let's address Evolution:
Evolution is the process of change in the inherited traits of a population from generation to generation. These traits are the expression of genes that are copied and passed on to offspring during reproduction. Mutations in genes can produce new or altered traits, resulting in heritable differences between organisms. Evolution occurs when these heritable differences become more common or rare in a population, either nonrandomly through natural selection or randomly through genetic drift.
In order for Evolution to occur, three criteria must be met (quoting our lecture notes specifically):
A. There must be genetic variation among members in the population.
1. Crossing over, the shuffling of genes and chromosomes during cell division, and the randomness of fertilization all contribute to genetic variation.
2. The original source of variation is mutation, which occurs about once in every 100,000 cell divisions.
B. There must be inheritance of traits by offspring.
C. There must be some form of selection - the survival and enhanced reproduction of individuals with favorable traits.
Now let's talk about "red heads":
The genetics of red hair, discovered in 1997, appears to be associated with melanocortin- 1 receptor, which is found on chromosome 16. Red hair is associated with fair skin color and sensitivity to ultraviolet light. The MC1R recessive gene, which gives people red hair and fair skin, is also associated with freckles, though it is not uncommon to see a redhead without freckles. Eighty percent of redheads have a MC1R gene variant, and the prevalence of those alleles is highest in Scotland and Ireland. The alleles that code for red hair occur close to the alleles that impact skin color, so it seems that the phenotypic expression for lighter skin and red hair are interrelated.
The inheritance of red hair is close to what geneticists describe as an autosomal recessive mode of inheritance. This means that the parents of red haired children may carry the gene for red hair but not have red hair themselves. There is also evidence that red hair may be an example of incomplete dominance. This means that when only one copy of the red hair allele is present, red hair may blend with the other hair color, resulting in different types of red hair including strawberry blond (red-blonde) and auburn (red-brown). (I had the latter, although lost most of the red pigmentation by adulthood).
Red hair is the rarest type of natural hair color in humans. The pale skin associated with red hair may be of advantage in far-northern climates where sunlight is scarce. Studies suggest that lighter skin pigmentation prevents rickets in colder latitudes by encouraging higher levels of Vitamin D production and also allows the individual to retain heat better than someone with darker skin.
Some scientist have suggested that the vividness and rarity of red hair may lead to it becoming desirable in a partner and therefore it could become more common through sexual selection. Others however, say that red hair is not the result of positive selection but rather the lack of negative selection. In Africa red hair is not selected because high levels of sun would be harmful towards fair skin. However, in Northern Europe this does not happen and so redheads come about through genetic drift.
Does this example meet the criteria of evolution? Absolutely.
If predictions by the Oxford Hair Foundation come to pass, the number of natural redheads everywhere will continue to dwindle until there are none left by the year 2100. The reason, according to scientist at the independent institute in England, which studies all sorts of hair problems, is that just 4 percent of the world's population carries the red-hair gene. The gene is recessive and therefore diluted when carriers produce children with people who have the dominant brown-hair gene.
How is this evolution taking place? By sexual selection, one of the two types of non-random changes in gene freguency and one of the four in the criteria for evolution of species.
This example points to the fact that we, as humans are evolving and we continue to evolve. Evolution is the central theory in biology. This class has already set forth an excellent example, I just wanted to bring up the idea of red-heads just to show you how cute I was when I was little! LOL
Artificial Selection is the intentional breeding of certain traits or combination of traits over others. It was originally defined by Charles Darwin in contrast to the process of natural selection. Humans either intentionally or unintentionally exert control over which organisms in a population reproduce or how many offsprings they produce, therefore, the distribution of traits in the organisms' population will change.
Somatic cell nuclear transfer (SCNT) is a laboratory technique for creating an ovum with a donar nucleus. It can be used in embyronic stem cell research, or in regenerative medicine where it is sometimes referredto as "therapeutic cloning". It can also be used as the first step in the process of reproductive cloning. This technique is currently the basis for cloning animals and in theory could be used to clone humans. Some people feel that because we have developed this technology that we are immune to natural selection, and this point is well taken. I personally can foresee a day when you can regulate what genes you want to pass to your offspring, determine the sex, height and appearance of your offspring, all of which will most certainly impact the theory of evolution. However, even with this technology available to date, I do not believe that this makes us immune to natural selection. Currently SCNT has a low success rate. For example, Dolly the sheep was created after 277 eggs were used. Out of those 277 eggs, only 27 created viable embyros, and only three of the embyros survived until birth out of which only one survived to adulthood. Although one day we may lower these statistics, natural selection will always come into play, eliminating those most severely mutated genes that face no viability.
What about Natural Selection?
Natural selection is the process by which favorable traits that are heritable become more common in successive generations of a population of reproducing organisms, and unfavorable traits that are heritable become less common. Natural selection acts on the phenotype, or the observable characteristics of an organism; favorable phenotypes are more likely to survive and reproduce than those with less favorable phenotypes. Over time, this process can result in adaptations that specialize organisms for particular ecological niches and may eventually result in the emergence of new species.
There are three types of Natural Selection:
1. Directional Selection - One phenotype extreme is eliminated from an array of phenotypes.
2. Stabilizing Selection - Both extremes are eliminated and the intermediates are selected.
3. Disruptive Selection - Intermediate phenotypes are eliminated.
There are three main components of Natural Selection:
1. Organisms have more offspring than can possibly survive.
2. Organisms must compete for limited resources.
3. Organisms with higher biological fitness survive, reproduce and pass on their successful genes.
For a moment now, I'd like you to take my hand and walk with me into a reoccuring nightmare I have at least twice a month. It starts with one word; pandemic.
A pandemic is an epidemic (an outbreak of an infectious disease) that spreads across a large region, or even worldwide. A prime example of pandemic is the Black Plague.
The Black Plague was one of the most devestating pandemics in human history. It began in South-western or Central Asia and spread to Europe by the late 1340's. The total number of deaths worldwide from the pandemic is estimated at 75 million people; there were an estimated 20 million deaths in Europe alone. The Black Plague is estimated to have killed between a third to two-thirds of Europe's population. Some scientist have suggested that the Black Plague contributed to the Little Ice Age. Pollen and leaf data, collected from lake-bed sediments in the southest Netherlands, supports the idea that millions of trees sprang up on abandoned farmland soaking up carbon dioxide from the atmosphere and thus cooling the planet.
Many people argue that medical techology has walked us pass this point of evolutionary disaster, that today we possess a "get out of jail free" card called antibiotics. Although I hate to be the bearer of bad news, I believe it's important that people understand for every "get out of jail free" card, there is of course a "property tax" card that comes into play and makes you wonder if you were better off hanging out in jail for the three rolls and fifty bucks. This "property tax" card is called "antibiotic resistance".
Antibiotic resistance is the ability of a micro-organism to withstand the effects of an antibiotic. It is a specific type of drug resistance. Antibiotic resistance evolves naturally via natural selection through random mutation. Once such a gene is generated, bacteria can then transfer the genetic information by plasmid exchange. If the bacterium carries several resistent genes, it is considered a "superbug". The antibiotic action is an environmental pressure; those bacteria which have a mutation allowing them to survive will live on to reproduce.They will then pass this trait to their offspring, which will be a fully resistent generation.
Although I am not one to subscribe to the idea of "waitting out a virus" and dealing with the discomfort it provides, I also realize that overuse and abuse of antibiotics is the prime reason these organisms are evolving and will continue to evolve until no known medication or antibiotic can eliminate the pathogen. This idea smacked me straight in the face when I learned about MRSA - Methicillian-resistant Staphylococcus Aureus. This pathogen, once only known among healthcare workers and hospital facilities is now emerging into the community. There is currently no antibiotic known to cure all types of MRSA and it appears that as fast as we invent a new antibiotic, the pathogen evolves generations that continue to live on against the battle with antibiotics. It should also be noted that during the last three influenze pandemics (1918, 1957-58 and 1968) infection with Staphyloccus Aureus was a common complication and contributing factor to the mortality rate of the pandemic.
In essence, pathogens fight against natural selection becomes our ultimate fight against natural selection, and currently no amount of medical technology can completely control this factor for humans. It is only the mere fact that we as humans (being the pompous asses we are) believe that we can take on this battle against nature (and thus looking at the "big picture", with God) and conceivably win. What could take place in this scenario however, is that human survivors of these pathogens would reproduce and make generations of offspring immune to the pathogen itself.
This my friends creates the ultimate answer to the question that has been set forth; Are humans in a technological world exempt from natural selection?