Physical Anthropology

Physical Anthropology and the Evolutionary Process



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Evolutionary Processes

Rosemary and Peter Grant, along with their colleagues, conducted a study in the Galapagos Islands on finches. During this study, something incredible happened that demonstrates a modern day example of evolution through natural selection.
The finches beaks had evolved so that each species had a beak that allowed them to survive on particular food sources. Unfortunately, however, in 1977, a drought hit the islands and so severe and lengthy that most insects disappeared and the only food source left was plant seeds that were bigger and tougher than those that the finches were used to.
When the islands' ecosystem returned to normal, the scientists found only 14% of the finches had endured the drought. The remaining finches were five to six percent larger and their beaks longer and deeper than those that had not survived. This allowed them to feed on the plant seeds available by cracking them open. Because males are generally larger than females, the number of males was much greater than females.
Since the females selected their mates, they chose those who were bigger and had stronger beaks than the rest which allowed for a change in gene frequencies. Consequently, the finches that hatched from this mating were larger and had bigger beaks as well. However, when the conditions returned to normal, the females no longer had to choose the males with the distinct advantage as the food supply was not in short supply. Therefore, the size of the next generations of finches returned to the previous size.
This research was very helpful in seeing natural selection taking place. As you can tell, if the food shortage would have continued, the finches size would have been much greater today than before the draught due to the natural selection process which allowed the species to survive.
Mutation is a large factor in evolution. It provides for new genetic variation, however, is inhibited by the definition of evolution which needs to include a change in allele frequency. Therefore, the only mutations that should be addresses for evolutionary purposes are those that occur in the gametes or in the cells that produce gametes as these are the ones that are passed on through generations and result in genetic change. They do this by making new versions of a gene or altering other details of the genetic code.
Genetic drift occurs when a population is divided and the separation does not result in two "symmetrical" populations. The allele frequencies of the new populations will vary from that of the original population. This splitting is called fission. These occurrences are important because they allow for different frequencies which allows the progress of evolution.
An example of genetic drift would be a population of Pennsylvania Dutch. One-third had the gene for Tay-Sachs disease which kills those with the recessive gene by the time they are four. This larger percentage can be explained by the fact that all of them were descendents of the couple that founded the population. It can be deduced that one of these two carried this gene that was continually passed from generation to generation.
The theory of evolution will, of course, always have those that disbelieve it. Since it is such a well supported idea, we, as a general population, consider it to be a fact. The problem occurs when people are torn between science and their belief system. Obviously, the science of evolution can not be disputed, but many hold the faith of their beliefs in higher esteem.
Those who believe the ideas that have not proven to be true, i.e. the Earth being flat, are said to practice "pseudoscience." Many of these people base their ideas on literal interpretations of the bible. This led the way to a rather new problem referred to as intelligent design.
Intelligent design is the idea that an intelligent designer (God?) played a role in some aspect of the evolution of life on earth, usually the origin or life itself. Now, this is, of course, and unscientific take on creationism, however, they believe that with all of the steps in the basic chemistry of life, it would be much to complicated to have come about naturally and would have had to happen through a supreme being.
The problems with this "theory" are the initial improbability of something happening doesn't preclude its happening and that it is not a scientific idea. For instance, from the formation of the earth to the formation of life, it took a billion years for just the right chemical combination to create and lead to life. There did not have to be any type of intelligent designer to make this happen. There were billions of chances for things to come together in almost infinite numbers of variations so even if that first chemical combination did not happen, it inevitable, would have sooner or later.
The second problem is that this is not a scientific idea. It is not testable. It is simply another version of scientific creationism. The evidence to support the standard theory that we have arrived at today far surpasses any ideas that have to be taken on faith instead of proven by scientific evaluation.
While there may be some great intelligent designer behind the universe, this is not a testable idea and does not have any basis on fact, it can only be taken on belief. One must come to recognize that even if this is what they choose to believe, they can not shut out the overwhelming evidence of evolution as presented today.

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