Williams: Evolution as a science – Roanoke Times

Evolution is a process whereby something turns into another thing often more complex and sophisticated. There are three kinds of scientific evolution: cosmic/chemical, biological and social. I will concentrate on the biological kind.

Cosmic/chemical evolution describes how after the Big Bang all 92 natural elements were synthesized. Hydrogen is the simplest element and created with the Bang. In stars it undergoes nuclear fusion to form the lighter elements. After aging stars often explode as nova and in this energy heavier elements are made. From these, solid planets like Earth form.

Biological evolution produces new types of organisms from previous forms or allows the process of speciation through a variety of phenomena. Two steps are necessary: genetic mutations and natural selection. Genetic mutation occurs because DNA undergoes chemical change producing new forms of the genes. Selection is the removal of some individuals from breeding populations. Natural selection acts on the differences though physical, chemical aspects of the environment, competition, predation, herbivory, parasitism and pathogenicity, and mutualism. Mutualism is where two types cooperate to the benefit of both.

Biological evolution shows specific patterns based on the various combinations of these events, Hybridization where two types interbreed results in a new third kind. Divergence is when two new species co-arise from a former one. Radiation occurs when divergence happens repetitively and many types come about. Convergence is the case of different species becoming more alike by a common environments selection, like birds, bats and bees which all have wings and fly. These processes have all been observed in the fossil record.

Evolution is actually measured by a science called population genetics. Population genetics is possible because a gene mutates and produces different forms of a gene for a trait. Geneticists count the numbers of all forms in a population and compare each of these to the total number of that gene, called the frequencies. If over time there is a change in these frequencies, scientists say evolution is occurring. A curious form of this, unique from the above, is genetic drift where the change is not selected but occurs randomly.

With all of this, the most common form of evolutionary change is extinction or complete disappearance of a species. This is observed in the fossil record and is occurring now at a rapid rate due to human pressures. Even an event like this is named, called a punctuation or extinction crisis due to large scale.

Human evolution is well recorded in the fossil record. This record is a layered sequence of recent evidence to older and older evidence as we dig deeper in sediments. About 50 million years before the present (B.P), the record shows the emergence through radiation of primates, which we are, including eventually monkeys and apes. Around 2.5 to 3 million years B.P. new types appeared, represented by fossils of australopithecines. These stood upright and had hands. A well-known example of these is the fossil called Lucy.

Diverging from these about 1.5 million years B.P. was the first of our genus Homo. First arose H. habilis that showed the ability to make stone and wooden tools and showed noticeable brain enlargement. After it and briefly before its extinction came H. erectus which was more fully upright and showed more brain expansion and tool facility, developing use of bone and animal hides.

Around 250,000 years B.P., fossils indicate the presence of our species, Homo sapiens. We have a much larger brain with a big prefrontal cortex and an enlarged forehead. Hand to eye coordination is very adroit and fine. The last refinements were seen 150,000 years B.P., probably with extensive hairlessness and with extensive cultural development. From hereon we find extensive, prolonged cultural complexity and eventually modern technologies. Most importantly, humans are the only Earth creature that has languages.

Social or cultural evolution is all the changes since 150,000 years B.P. A culture is a grouping of social practices common to a human group. Starting with stone, wood, bone and hide technologies, we have become increasingly sophisticated, developing more than 5,000 languages (which also go extinct), forming many, many cultures, and making many changes in technological capabilities. Today we have computers, wireless techniques, robots and sadly ever more elaborate ways to kill each other.

The question now is our own extinction. All this knowledge weve gained must be good for something. Lastly, many authors have written about these things. A good one is Thank God for Evolution by Michael Dowd.

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Williams: Evolution as a science - Roanoke Times