Reframing Evolution: Part 2 – What is Evolution?

by / Saturday, 18 May 2013 / Published in Evolution vs. Creation

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In Part 1, we discussed the importance of reframing Evolution. For the next three posts, we will be discussing exactly what the theory of Evolution is. Nothing here contravenes scientific consensus. We will merely set the stage for the critiques and refutations which will be presented in future posts. For further information on any of the below, I recommend checking out the Berkeley website on Understanding Evolution, which includes many helpful articles and resources for learning about evolutionary biology from the perspective of its proponents. A sound understanding of the science and logic of evolution is a prerequisite for any serious critique.

Pillars

The theory of Evolution has two pillars.

1. Genealogical Continuity (GC)
2. Natural Selection (NS)

GC is the idea that all organisms have progenitors, i.e., parents. If all organisms have progenitors, this means that there is a long line of ancestors for each living thing on the planet. You can imagine a long chain that connects each organism with its ancestors in the distant past. According to GC, these chains of descent will intersect such that most or all organisms fall on the same family tree. Genealogical Continuity is an old idea that predates Charles Darwin and perhaps even the ancient Greeks. Some historical background on GC will be presented here.

GC faces three initial problems:

1. The Origin Problem: How did life begin?
2. The Complexity Problem: How did life forms become so biologically complex?
3. The Diversity Problem: How did life on earth become so diverse?

Darwinian Natural Selection provides what seems at first like an elegant solution to these problems (hence, Charles Darwin’s meteoric rise to success and fame) . If Genealogical Continuity is the “what” of Evolution, then Natural Selection is the “how.”

What is Natural Selection? The idea itself is quite simple and persuasive, and therein lie the keys to its popularity and success. To state it in a general way, NS is the explanation for how organisms change from generation to generation due to conditions in their ecology.

Phenotypes and Genotypes

The most basic way to understand how this works is to imagine a population of some animal species. Within that species, there will be some variation in characteristics from one animal to the next. This is called phenotypic variation. A phenotype is the collection of all of an organism’s traits. For example, a polar bear’s phenotype includes white fur, teeth, claws, its ability to swim, hunt, etc. These traits are understood to arise from the organism’s genes, or genotype. Often, differences in phenotype are the result in differences in genotype. For example, blue-eyed and brown-eyed individuals have differences in the genes responsible for eye color.

An organism’s phenotype directly or indirectly contributes to its ability to survive and reproduce. For example, a polar bear that does not hunt will not have very high chances of surviving in the arctic. Similarly, a dark-furred polar bear will have more difficulty catching prey than a lighter-furred bear. The dark bear will have a harder time finding food and hence surviving. Rate of survival, of course, directly correlates with rate of reproduction. Animals that do not live long are not around to reproduce or take care of their young.

In this way, certain members of a population will reproduce more than other members simply because of those particular aspects of their phenotype that proves advantageous in the ecology. This variance in reproductive success results in a variance in the prevalence of genotype in the population. Those organisms that are better at reproducing are better at spreading their genes. Thus, the trait that gave them the reproductive advantage in the first place proliferates in the next generation.

Slow and Steady Change

With time, the genetic profile of the species continues to change and adapt in accord with the natural changes that occur in the ecology. Over a long enough period of time on the order of millenia, new species arise and others go extinct. What was once one species may split into two separate species and so on. Biologists widely hold, for example, that humans and chimpanzees share a common ancestor species from which they both arose. If one goes far enough back in time and far enough along the family tree, one can pinpoint the ancestor species from which most contemporary species descended.

This is evolutionary theory in a nutshell. In the upcoming series, we will, inshaAllah, further examine and critique these two pillars: Genealogical Continuity and Natural Selection, respectively. ♦

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