Yesterday I got an interesting comment on a previous post on evolution.
I thought my answer would be to elaborate for a reply, hence this reply-post.
Tias Dailey writes the following (bolds are mine):
“You wrote that in one winter, a population of birds could be affected by natural selection because the small birds die off, leaving the larger birds. The thing is, natural selection always has a narrowing effect on the variation in a population. Understand that in your scenario, large birds did in fact exist before the natural selection. So that in itself is not evolution, but only narrowing of the gene pool. So that scenario doesn’t show that evolution can occur quickly.
To show that evolution can occur quickly, you would need to show that new features can arise quickly—features that were not present before.”
In fact, Tias makes 2 statements here :
- Natural selection always has a narrowing effect on the variation in a population.
- Narrowing of the gene pool in itself is not evolution.
- Change in the genetic composition of a population during successive generations, as a result of natural selection acting on the genetic variation among individuals (the free dictionary)
- Biological evolution … is change in the properties of populations of organisms that transcend the lifetime of a single individual. The ontogeny of an individual is not considered evolution; individual organisms do not evolve. The changes in populations that are considered evolutionary are those that are inheritable via the genetic material from one generation to the next. Biological evolution may be slight or substantial; it embraces everything from slight changes in the proportion of different alleles within a population (such as those determining blood types) to the successive alterations that led from the earliest protoorganism to snails, bees, giraffes, and dandelions. (talkorigins)
- Biological evolution is defined as descent with modification. Biological evolution occurs at different scales. These include small-scale evolution and broad-scale evolution. Small-scale evolution, also referred to as microevolution, is the change in gene frequencies within a population of organisms changes from one generation to the next. Broad-scale evolution, also referred to as macroevolution, refers to evolution at a grander scale. It focuses on the progression of species or entire clades from a common ancestor to descendent clades over the course of numerous generations. (animals.about)
- Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins. (Wikipedia)
- This IS change in genetic composition.
- This IS inheritable.
- This DOES change gene frequencies
I love how your post is logically structured, and how you distilled my statements into their logical points. I see that you disagree with my statement that narrowing is not evolution. But that is because we both have different definitions of the term “evolution.”
You listed a few definitions that said that evolution is simply change, in whatever direction. People say this a lot, and it sounds true. After all, genetic changes are random, as well as natural selection. But remember the overall direction of evolution so far.
Generally the trend of evolution should be “upward,” which means more genetic information to code an organism’s features. From the first bacterium to the present complex and diverse organisms, there was an upward trend. More DNA codes were added over time. Today, the general direction of evolution is downward. We see that genetic modification is very destructive to an organism.
That was a bit off topic. My main point is this: from the first organism to today’s more complex organisms, evolution did not occur via narrowing of the gene pool. That would imply that the first organism was incredibly genetically diverse. The theory of evolution basically has two steps: genetic mutation and then natural selection. Mutation is supposed to yield new features or genes, and then natural selection narrows the gene population to exclude the non-evolved organisms.
My main point was that in order to look for evidence that supports the overall supposed direction of evolution, you need to look at genetic modification and not natural selection. Because genetic mutations are the driving force. Natural selection can’t “add” anything.
I look forward to your thoughts on this.
Tias
By: Tias Dailey on November 15, 2011
at 4:12 am
Hi Tias,
I think we do agree after all.
Although evolution can be downward, it is indeed clear that the general trend is upward. Not only in the sense of more genes, but more generally in the sense of more levels that are added on top of eachother controlling the lower levels (like new sorts of genes that control other genes etc…). I mentioned this for instance in previous posts http://bit.ly/v4xLyk and http://bit.ly/sJP0Lt
zyxo
By: zyxo on November 15, 2011
at 8:45 pm
Evolution And Natural Selection
http://universe-life.com/2011/12/23/evolution-and-natural-selection/
Natural selection is energy (E) temporarily constrained in a mass (m) format.
Evolution is the sequence of processes between physical states ordained by natural selection.
Evolution Is The Quantum Mechanics Of Natural Selection. Period.
Dov Henis (comments from 22nd century)
http://universe-life.com/
By: dovhenis on December 23, 2011
at 4:51 pm