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Biology

[1] SOME THOUGHTS ABOUT EVOLUTION

by Timothy Howell, Low Voltage Consulting Engineer

One of the most misunderstood topics in Christian communities and in society at large is that of evolution first proposed by Charles Darwin in his book origin of the species published in 1859 and later modified by other scientists in the 19th and 20th centuries. Many people who discuss and debate this topic are confused or ill informed as to the meaning of the terminology. This article will briefly survey what evolution is and is not, and define terms in order to bring some clarity to the discussion. The reader must understand that this article only introduces the topic and those who are interested in the subject should consider additional online research or classes for further study.

Defining some terminology

Evolution can have up to five different meanings–macro and micro evolution, chemical, microbiological, and speciation evolution.

Darwinian Evolution

The best place to begin is by discussing the concept most people think of when they hear the term evolution–Darwinian or macro evolution. This is the idea that all life descended from a common ancestor, from an original single-celled organism and was modified by environmental pressures present at different times through history (Darwin, 1859). For example, as species moved into new areas they adapted to the new environments by developing capabilities that over time gave them an advantage over other members of their species. As drought conditions persisted on a savannah for long periods of time, some species might respond by adapting to consume leaves from trees instead of grasses. Predation is also considered to be an evolutionary pressure. This implies that some herbivores would develop natural defenses against predation such as climbing, or running fast. As the theory goes, these herbivores would be selected by evolution as the fittest, and therefore would survive as a species while other species that presumably could not adapt would become extinct. The driving force thought to be behind evolution is the innate desire of all species to propagate themselves by passing on their genetic information to the next generation. The key idea to remember about macro evolution theory is that it seeks to explain how new species are created from older or ancestral species over time.

Adaptation

Adaptation, or micro evolution, is a theory that seeks to explain how members within a species adapt to changing environmental pressures over much shorter periods of time. New species are not created. The idea is that the genetic allele or characteristic for a favorable adaptation to a new environmental condition is present, and as this characteristic is expressed, it gives an organism an advantage for survival. (An allele is variation of a genetic trait, examples would be things like differing hair color or eye color in human beings.)

As these individuals reproduce they pass that advantage to the next generation, while other individuals within that species would presumably not survive as a result of lacking the specific adaptive advantage. Genetic drift is a term given to mutations that normally occur in a species over time. The mechanism by which it is thought to work is that over time various genetic alleles occur in populations with increasing or decreasing frequency.

Speciation

Speciation is less well known and is closely related to micro evolution. Here, a single species can separate into two species as a result of geographic isolation. This resulting separation, combined with normal genetic drift and mutations occurring over time will cause the original populations to diverge to the point at which interbreeding is no longer possible. The best natural example of this would be the various finch species of the Galapagos Islands (Speciation in real time, 2010). See the citation for more information.

At this point, we need to understand that defining a species is more difficult than it seems. Generally, for mammals, birds, fish and reptiles, a species is a group of similar individuals that can reproduce and provide viable off spring (Defining a species, n.d.). This seems reasonable but it is difficult to apply in the world of microorganisms to prokaryotic (bacteria) and eukaryotic (single cell organisms) species that reproduce asexually. On the macro scale for example, a mule is a hybrid cross between a jack donkey and a mare horse. The mule cannot interbreed and produce viable offspring. The only way to get another mule is to hybridize a donkey and horse. Is a mule therefore a species? This is the problem.

Microorganism Evolution

Microorganism evolution describes changes in prokaryotic organisms over time. Prokaryotes are organisms that a structurally different from the cells that make up birds, mammals, and reptiles. The prominent difference is that these cells have no nucleus. Athough they do have DNA, it is organized in more of a ring structure and not organized into chromosomes. One of the really interesting experiments involves Michigan State University in the Laboratory of Dr. Richard Lenski. Here, Lenski and his team of researchers have recently surpassed the fifty thousandth generation of E coli in an experiment called the E. coli long term experimental evolution (Lenski, 2010). The experiment, in simplest terms, compares previous generation E coli to recent generation E coli bacteria to see how they change over time. The researchers use bacteria because the generational times are short (the experiment has been running a little over 20 years). Here is what Lenski says about some of the results of the experiment. “The individual cells in all twelve lineages are larger than their ancestors, and all are more efficient at using the glucose in the culture medium we grow them in. Also, all twelve lines have similar mutations in several genes. In other ways, however, they have diverged, including a striking case where a single lineage evolved the ability to consume citrate, another source of energy in the medium, but one the ancestors could not exploit. In fact, a characteristic feature of E. coli as a species is that it cannot grow on citrate. We are now investigating the series of mutations that enabled this transcendent change” (Lenski, Evolution: Past, Present and Future, n.d.). This is a very interesting experiment that bears watching. It should be noted however that even after fifty thousand generations of reproduction the E coli bacteria, while able to digest different food sources and glucose more efficiently and being larger in size, is still E coli and has not become a new species. This experiment shows that the bacteria are adaptable and the process is more akin to micro evolution discussed above.

Chemical Evolution

For evolutionary theorists, chemical evolution is the toughest nut to crack. Chemical evolution seeks to describe how the original ancestor, that first cell or small population of cells arose from the primordial goo. As of now there is no coherent theory to describe how the first cell(s) could have arisen from component building blocks. Indeed, there are a great number of issues to overcome that include the UV/O2 paradox, RNA self-replication and formation, and homochirality (Deem, 2001). The UV/O2 paradox is a problem because oxygen is a highly reactive element, second only to fluorine on the periodic table of the elements. Elemental oxygen is an effective biocide that breaks down chemical bonds of organic molecules. O3 or ozone, however, is required to be in the primordial atmosphere in order to protect the surface of the planet from harmful ultravilot radiation that also destroys the chemical bonds organic substances. This becomes the classic “can’t live with it and can’t live without” it problem. RNA self-replication was proposed as a means of getting around problems associated with replication of many thousands of proteins (enzymes) needed in a cell. No mechanisms have ever been found, however, by which RNA can replicate itself. This is only done with the help of, and in the presence of, enzymes that must already exist. Again the classic chicken or the egg problem.

Finally there is the problem of homochirality. Organic molecules used as building blocks of life, specifically amino acids used to synthesize proteins, can have a left-handed or right- handed orientation that are nearly mirror images of each other. Only the left-handed version is used for building blocks. DNA, messenger RNA, transfer RNA and ribosomal RNA all code for left-handed chirality. Laboratory experiments show that, all things being equal, by combining reactants statistically both versions are developed for simple amino acids. No known method or theory is able to explain why-left handed chirality is dominant and became dominant in early life. The only plausible explanation for a single cell to have developed is if both the enzymes and RNA/DNA molecules constituting a cellular organism arrived at about the same time.

Conclusion

Evolution is a complicated and often emotional subject to discuss. Much skepticism surrounding Darwinian evolution arises from its being based primarily on lines of evidence from micro evolution / adaptation, speciation and microorganism evolution. The evidence is compelling that all creatures, including human beings can adapt to what are called evolutionary pressures including changes in climate, food and water sources, predation and necessity. The adaptation of creatures, however, can also be explained very well in terms of design by a Creator.

As a control systems engineer, I design systems and software to be robust and able to discern and adapt to some extent to new situations. As a psychologist, I see the robust nature of the human mind. In my opinion, design has a greater explanatory power than an unguided, undirected, naturalistic evolutionary process.

As you might have also gathered, due to a lack of evidence, chemical evolution has many issues to overcome as well. The best explanation for the appearance of the first cells of life suggest that everything has to appear at once in order for a working cell to function. For further study, I encourage the interested reader to investigate some articles on the reasons to believe website www.reasons.org and this site as well.

References

Darwin, C. R. (1859). On origin of species by means of natural selection. London: Murray.

Deem, R. (2001). Origin of life: latest theories/problems. Retrieved from www.godandscience.org: http://www.godandscience.org/evolution/rnamodel.html

Defining a species. (n.d.). Retrieved from Understanding Evolution: http://evolution.berkeley.edu/evolibrary/article/evo_41

Lenski, R. (2010). E. coli Long-term Experimental Evolution Project Site. Retrieved from Experimental Evolution: http://myxo.css.msu.edu/ecoli/index.html

Lenski, R. (n.d.). Evolution: Past, Present and Future. Retrieved from National Science Foundation: http://www.nsf.gov/news/special_reports/darwin/textonly/bio_essay1.jsp

Speciation in real time. (2010). Retrieved from Understanding Evolution: http://evolution.berkeley.edu/evolibrary/news/100201_speciation

Timothy Howell is a low voltage consulting engineer, living in Cedar Park, Texas.  He is currently working on a master’s of science degree in general psychology from Grand Canyon University and holds a B.S. degree in engineering from Texas Tech University.

 

 

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