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