How to make the selection single mode?

The counter-argument to the limitations of natural selection does not seem to make sense! Any ideas?

• Hello. I'm writing a report for a class in university, and I have been researching and analyzing various resources on the connection between natural selection and evolution, including all the related theories such as variation, adaptive radiation, and speciation. These are the two points that I discovered (please correct me if I'm wrong, I could have misinterpreted the original sources as I read them): 1. Evolution means the emergence of a new genetic trait, which means the emergence of a new species. In natural selection, genes are DEPLETED to express the more favourable characteristics, not created. In an eliminative process such as this, a creative and innovative process like speciation cannot occur. 2. However, in Darwin's observations, a single ancestral species from Central or South America moved to the Galapagos Islands, where they occupied different niches and thus required to develop characteristics that are suited to the diet available on each of the islands. This lead to adaptive radiation where the finches eventually split up into 13 species - that is, speciation. This does not make any sense to me. What I don't understand is that in point 2 speciation has occurred from natural selection, even if the finches underwent the depletion process of natural selection instead of any introduction to new genetic traits. Why? And then, this violates the statement in point 1 that speciation cannot occur from natural selection. Any contributions to clarifying this problem are appreciated!

• Answer:

  First, an obvious word of caution. There are people in this world who openly oppose evolution. If you read these people when trying to *understand* evolution, it is guaranteed not to make sense ... because an *opponent* of an idea has a vested interest in explaining it in a way that ultimately leads to an illogical conclusion. If you want to understand *ANY* idea before deciding whether to reject or accept it, then you don't go to *opponents* of that idea first to explain it to you! You start first with the supporters of the idea (in this case, just about any scientist or text book) to get a good, foundational understanding of it ... and THEN you can read the arguments for and against that idea with an informed mind. I say this because somebody has given you truly *INCORRECT* information about the basics of evolution, and natural selection. Explaining natural selection as a "depletion" or "eliminative" process is one you will find only in *anti-evolution* literature ... not one that you will find in any science textbook, or book written by an actual scientist who both understands and supports evolution. So let's start at the beginning. You start with a definition of 'evolution': >"1. Evolution means the emergence of a new genetic trait, which means the emergence of a new species." Unfortunately, this is an incorrect definition of 'evolution' in many ways. (a) Evolution is defined as the "change in inherited traits of a population over generations" ... or in the language of genetics, "change in allele frequencies of a population". That's it. (b) It is NOT the "emergence of a new genetic trait" unless by emergence you mean the propagation of the new trait into the species. I.e. I caution against the fuzzing of the idea of the emergence of a new trait in an *individual* (like a different-sized beak), which is NOT evolution ... versus the propagation of a new trait in a *population* (the average size of beaks getting longer), which IS evolution. (c) The emergence of a new trait is NOT the same as the emergence of a new species. (This is not even logically true.) New traits can emerge with or without a new species emerging as a result. The propagation of new traits ... regardless of whether speciation occurs as a result ... fall under the same banner of 'evolution.' > (continuing) "In natural selection, genes are DEPLETED to express the more favourable characteristics, not created." This is misleading. Nowhere in your description does the word 'mutation' appear. Mutations are tiny errors in replication. These are constantly *changing* existing genes, and *adding* new ones. Some of these changes and additions are harmful, some are beneficial, most have no immediate effect at all ... they are 'neutral' mutations. Natural selection is the act of "nature selecting" (hence 'natural selection') any combinations of these new mutations that provide some minor improvements to existing traits. So yes, natural selection can be seen as "eliminating" bad genes, but it is also *adding* new genes (both neutral and beneficial) to the gene pool. It's important to understand that a mutation can indeed *ADD* a new gene to an *individual* that did not exist in its parents or ancestors. And if that new gene confers some benefit to that individual or one of its descendants, then natural selection is indeed *ADDING* that gene to the collective gene pool of the population, by 'selecting' that individual's descendants to make more offspring. Genes are rarely completely "depleted". That is why human embryos temporarily express the genes for building gill folds, webbed fingers, and tails. The fact that these are expressed early in the embryo, and then disappear is evidence that the genes are *STILL THERE*, but suppressed in the adult. Further evidence that genes are not "depleted" nearly as often as they are *ADDED* is the fact that as much as 98% of our DNA is "non-coding DNA" ... it doesn't seem to code for anything at all! The fact that there is SO MUCH non-coding DNA, is evidence that there are lots of mechanisms for the addition of new genes, and very little removal of old genes. They are like the junk that you accumulate in your garage as you move from house to house ... for the most part they are ignored ... but every once and a while during a move (the replication of a new individual) one of these old boxes gets opened by mistake (the gene is expressed), and a child is born with a tail, or a dolphin is born with tiny legs, etc. So it is clear that evolution by natural selection *ADDS* more genetic information than it ever "eliminates." >"In an eliminative process such as this, a creative and innovative process like speciation cannot occur." In logic arguments, this is what we call the "payoff". By starting with an incorrect definition of evolution (as "production" of new traits and species), and an incorrect explanation of natural selection (as an "eliminative process") ... they have set up the punchline ... evolution by natural selection is illogical. It is going from saying that (A) some genes are eliminated by natural selection (which is true); to (B) therefore natural selection is an *entirely* "eliminative process" (which is FALSE and does not follow); to (C) therefore "a creative process like speciation" cannot occur (which is not only DEMONSTRABLY FALSE, but does not follow logically from A and B!). First, speciation occurs. We have documented it in the lab! See here: "Observed Instances of Speciation": http://www.talkorigins.org/faqs/faq-speciation.html "Some More Observed Speciation Events": http://www.talkorigins.org/faqs/speciation.html Second, speciation itself is not a "creative" or "innovative" process. That "creative, innovative" process is everyday evolution (mutations throwing out lots of tiny variations on existing traits, and natural selection *selecting* only the useful ones). Speciation is just one consequence of a "creative, innovative" process that is already occurring ... namely mutation + natural selection ... when it encounters a third element *reproductive isolation*. Which brings us to point 2 ... Darwin's finches. That is precisely Darwin's point. Natural selection explains why the same ancestral species, exposed to two different environments, produces different adaptations. It is *nature* (the environment) that drives this "creative, innovative" process called evolution. Natural selection *IS* "creative, innovative" ... it is NOT just "eliminative." And Darwin's second point is that when this "creative, innovative" process called natural selection, ALSO encounters *reproductive isolation* ... the result is *speciation*. The two populations have accumulated so many differences that they are no longer compatible for breeding ... they have *speciated*. So the reason that Darwin's finches (2) seems to contradict (1) ... is because (1) is a completely illogical and incorrect definition of evolution and natural selection. Summary: The argument is that evolution by natural selection is a "depletion" or an "eliminative" process and therefore cannot lead to a "creative, innovative" process like speciation. Evolution by natural selection is NOT "eliminative" ... because it includes the process of MUTATION. Constant mutation + constant natural selection TOGETHER is a very "creative, innovative" process, that can lead to huge "creative, innovative" results ... from the changing of beaks in an island-isolated species of finch, to the branching of multiple species of finches as a result, to the constant branching of new species as Time stretches on into the millions to hundreds of millions to billions of years.