- #51
bobze
Science Advisor
Gold Member
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Hey Dave,DaveC426913 said:
The fact of biological evolution is simply the change in allele frequencies in a given population from generation to generation.
The theory of evolution, explains why and how these changes occur. For example, one such aspect is Natural selection. Which occurs when Darwin's 4 postulates are met. Those being;
1. Individuals within a population vary
2. Some of that variance is passed on
3. More offpsring are produced than can be supported by the environment
4. Survival is not random, the best combinations of variation are more likely to survive and reproduce.
Its important to note however, that we have come a long way since Darwin's day and we know that NS is not the only selection process nor determinant frequencies of a evolutionary lineage. Things like sexual selection, genetic drift, epigentic inheritance (though this is a much newer idea, there is some interesting evidence nonetheless) all play important rolls in how allele frequencies are maintained.
People quickly get confused when confronted with this definition of "evolution", because people tend to think of evolution in snap shots (really a fault of our nervous system imo). I find it best, when explaining how these small changes in allele frequency manifest to make the biodiversity present on Earth today to use an analogy.
I like color bars for illustrating an evolutionary lineage the most, so bare with me for a moment while I explain. It also, imo, better explains transitional fossils as well.
First I think it maybe important to define what we are talking about here. What is a transitional form or fossil? Or even a missing link for that matter?
To understand this we need to understand a bit about species, more importantly lineages.
All life today and throughout the history of Earth can be thought of as a continuation or a branching of a lineage. Species is a concept we use to making talking about organisms easier. Species are not real, it is just a man made concept given name. The point where one species begins in history and another ends is arbitrary, because a species is not a set thing --We think this is so, because our perception of time and our short stay here on earth.
Its best to describe life as a descendant of a lineage. A lineage therefore, is a ancestor and all of his descendants --An unbroken line. In this case though, we are referring to populations as ancestors and populations as the descendants.
http://mediagods.com/tools/images/spectrum.jpg
I think the easiest way to picture it is to think about the color spectrum.
(For the sake of me not having to create a new color bar with a time scale, please imagine time 0 starts on the left hand side and increase going right to the end, which represents present day)
He we can think of the ancestor as one single point (a hue, saturation and value) on the left hand side. The population descendants then are the colors that follow toward the right. Each point is slightly different from the first, Just as in biology each generation's allele frequencies slightly differ from their parent generation.
We apply the term species to a whole grouping of colors, the species red for instance. But in reality each generation is slightly modified from the next, such that we have this slow transition from color to color (what we might collectively lump together as species).
This then means, that each slight change in gradient is a transitional form. Because looking at the past, we can see in every "color generation" slight modification from the previous generation.
This also means that every generation is a transitional form.
The consequence of this is that "transitional forms" as you and other creationists demand is a human construct which only is representative of a snap-shot of evolutionary history --In hindsight as well.
The other consequence of this is that all fossils are transitional, as they are representative of only that generation of organisms.
For example, were I to find a fossil of the RGB value FF3030 which corresponds to the color:
then I know (with the completeness of this color spectrum) that it is transitional. A transition between the populations FF3029 and FF3031. Granted the 3 populations may look nearly identical to the naked eye, but at the populations genomic level they differ.
So you ask to see a transitional fossil? Head to your nearest limestone quarry and spend some time looking at the stones --All of those fossils encapsulated for time immemorial are your evidence.Let's talk for a moment of missing links and why this is such a poor concept.
Often growing up we were taught science is "searching for the missing link". One day well find it and piece all of our evolutionary history together. This is a lie, one created by media and high school science teachers who seemed to lack and interest in teaching real science.
Missing link implies evolution is a large step process. Going back to the color bar, we might say the missing link between the "red and green species". But, if we find a representative of that "yellow species" what have we done? We have opened the door for the need to find two more missing links, one on either side of the representative yellow species.
Whats worse, is the concept implies that our color evolutionary history went from red to yellow to green. What we have done is gloss over the thousands of slightly different hues that occur in between them.
Edit: apologies not sure how to display a picture, is that allowed here?
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