The big picture on theory of evolution

After reading Sara Rockhey’s letter, published on June 23, 2005, I felt that a response is needed.

I agree with her about how science is conducted. It must be based on observations, be measurable, and be repeatable, however it also must be testable. This is the basis for the scientific method, the way in which scientist gain knowledge about the natural world that surrounds us. Once the observations, measurements, and testing have been done, there are two possible outcomes: first, a scientific law, which is a description, usually mathematical, of nature; and second, a scientific theory, which explains the “why” and “how” of things in nature. Newton’s laws of motion describe the path an object will take when it is in motion, but it does not explain why the object will take that path. The atomic theory explains why and how atoms interact, and gives us a model to use in studying the basic building blocks of matter. Scientific laws don’t change with time, while scientific theories change as we learn more. Atomic theory has changed greatly since the ancient Greeks first proposed that matter was made of indivisible particles called atoms.

Theories are based on observations, measurements, and testing, but they go beyond the group of hypothesis (possible explanations that have withstood testing) that they are based on. A theory must make predictions that are testable. A theory is useless unless it can be tested. Atomic theory and the theory of evolution are both testable theories. The theory of evolution makes predictions about how and why organisms change with time. We see these predicted changes when we look at domestic animals, the finches on the Galapagos Islands, the Tinian Monarch, the Guam Rail (Koko) or the peppered moth, plus other examples that are too numerous to list. The theory of evolution also explains what is found in the fossil record and in the genetic relationships between different organisms. The theory of evolution is a sound scientific theory and not a “non-scientific theory” as stated by Ms. Rockhey.

As for Ms. Rockhey’s assertion that one of the color varieties of the peppered moth should have been eliminated, she did not mention in her letter the affect of environmental variation and its role in natural selection, which would help to preserve both varieties of moth. A given environment is never uniform, and both the light and dark variety of the peppered moth may be able survive if they can find a suitable place to live in their environment. For example, the light form is found on trees with light lichens and mosses. If the tree does not have these lichens and mosses, the dark form is favored. When the industrial revolution happened, it caused the mosses and lichens to die on the trees in polluted areas, thus favoring the dark form of the peppered moth. In the countryside, the trees still had lichens and mosses, and the light form of the peppered moth was favored. So both color variations of the peppered moth can survive in nature because of variations in their environment, which is one of the predictions of the theory of evolution.

As for her statement “about 99 percent of the peppered moths were light-colored” before the industrial revolution, I would be very interested in the source for this statement. All I can find is that the dark form of the peppered moth were more noticeable after 1850, with no mention of percentages. In science, one needs to be careful when mentioning numbers (especially percentages), and to double-check the facts so as not to misinform readers and students. For more information about the peppered moth and the controversy that surrounds it, I suggest the following web site: http://wiki.cotch.net/index.php/Peppered_moth

Ms. Rockhey is correct that natural selection can eliminate traits in a population of organisms, but the law of natural selection is not the whole theory of evolution. The law of natural selection is only one small part of the theory of evolution, and this theory, as with all scientific theories, must be considered in its entirety to be properly understood. The theory of evolution does provide a method for how the many different traits found in a species are created. They are created by random changes in the genetic material of organisms, either by mutations or the process of crossing over of chromosomes that happens when gametes (sperm and eggs) are produced (in addition to other methods for introducing genetic variation.) These changes in genes result in the variations found in individuals of a species, which through the process of natural selection may lead to the creation of a new species with time.

The theory of evolution does not violate the second law of thermodynamics, as Ms. Rockhey states when she writes, “in truth evolution directly contradicts a scientific law, …”. The second law of thermodynamics states that in a closed system (nothing coming in from the outside) it will go from order to disorder—entropy. To overcome entropy energy must be used. Lucky for us, the Earth is not a closed system. We receive energy (sunlight) from the Sun, which is outside the Earth system. Life uses this energy to overcome entropy and to create the wonderful complexity that is found in nature. For a brief explanation of the second law of thermodynamics and how it relates to evolution, I suggest the reader visits the following web site: http://en.wikipedia.org/wiki/Second_law_of_thermodynamics

Finally, the theory of evolution is the best explanation we have for the large diversity of life found on Earth and the genetic relationships among the different species. The theory of evolution is the basis for modern biology and genetics. Without it, today’s understanding of life would be lost or still shrouded in mystery.

Howard Cole
Marpo Valley, Tinian