Evolution: The Basics

Posted on July 12, 2011 by



This is the first in a series of posts on evolution. While this deals with a misconception or two, this isn’t intended to be a defense of evolutionary biology -most here would seem to accept it anyway – nor to fully explain the field. Instead this is sort of an introduction that hopefully will be of some use to most here, and will serve as a reference for future posts on the topic of evolution or on other related subjects such as human biodiversity.

Evolution does have some implications for theology and philosophy. Like all branches of science evolutionary biology is materialistic in philosophy and practice. That is, the body of knowledge that comprises evolutionary biology is based upon historical investigation, and when practicable, the scientific method.

While some Christians may think otherwise this does not directly have anything to do with the origin of life or the Universe in general. Evolutionary biology is silent as to whether there is a purpose behind any of it as this cannot be investigated by the tools available to science. The same thing goes for theories of Intelligent Design, though that is beyond the scope of this article, and will be covered in the future should there be any demand for it. Also, to correct a misperception that is sadly surprisingly common among the general populace, although probably not held by most here -at least none that would admit it – humans did not evolve from apes. There was a common ancestor at some point in the past and the modern human and modern ape lineages were split from this point in time forward.

  EVOLUTION

What is evolution?  Evolution is the change , over a period of time, of the inherited traits of organisms. This change can be observed in real time in colonies of bacteria and populations of fruit flies among many other short lived (to humans) organisms. Over a long enough period of time via various methods of selection and mutation a new species -defined as an organism that has reproductive isolation and thus cannot mate with other types of organisms – emerges. These changes are recorded in the organisms genome, genome being defined as the complete collection of all the genetic material of the organism. Usually “genetic material” means genes or in other words, encoded traits such as height, eye color, etc. An organisms genome describes the proteins that make up the majority of tissues and other biological organs that enable the organism to live, and is passed on to any offspring that the organism has. The predominant carrier of genomic information would seem to be the molecule DNA, via the process of transcription although there do seem to be other methods, some unknown , of recording genetic information. See the following link for an example:

Research!
There are 2 primary methods of modifying and transmitting genetic information:

Selection

There is both natural selection (done by “nature”) and artificial selection (done by an intelligent entity). Basically, the genome of every organism changes over time. Despite various methods of conserving the genetic code, the sheer amount of information to be copied from generation to generation inevitably leads to errors in the code, often via such events as a point mutation or gene migration. However it happens, the individual organism exists in a certain physical environment and combined expressed traits of the genome of the organism may give it an advantage or disadvantage in terms of reproductive success in that environment. An example might be a giraffe. If, for whatever reason food tends to be scarce on land and relatively abundant in trees then the selective pressure would be for longer necks or other methods of getting at the more abundant food source. Thus traits are conserved and passed along, or eliminated or suppressed in the genome, and over time this leads to changes in the progeny of the organisms themselves. The human breeding of dogs is an example of artificial selection – humans become, in effect, the dogs “environment” and select mating partners among dogs and pups in litters based on the traits we wish to preserve. Note ONE IMPORTANT THING about both natural and artificial selection: as the picture above this post shows, selection “fitness” is relative to a given environment. If people with a sub 70 IQ had some genetic traits such that a very virulent disease would not kill them or kill as efficiently, then , eventually, evolution might select for a sub 70 IQ. So, unlike the popular misunderstanding, selection does not always equal “better” in the way in which we normally use that term.

Epigenetics

Epigenetic mechanisms are the other way in which genetic information may be modified and thus passed down. This is sort of a modified version of lamarckism . We do not yet know all the various epigenetic mechanisms. What basically happens in an epigenetic event is that the physical environment a parent organism is exposed to affects changes in the expression or repression of various traits of its child. In some cases, these can be passed on generation to generation, instead of merely from parent to child, the child’s children would also express the same traits. In epigenetics the underlying genetic code is not changed, however different parts of it are turned on and off based on environmental factors either outside or inside a womb.

At the present time, not everything is known about either the genome nor evolution itself. The field seems to be progressing rapidly, and thus as we understand more about how our genome and how it is expressed we should also understand more about the history of our evolution as a species and in what direction we are likely to continue to evolve. And that’s not even considering genetic engineering…

Good linkies below:

Link 1

Link 2

Epigenetics!

Link 4