Does the neutral theory of molecular evolution contradict Darwin's idea of natural selection?

[The Great Red Dragon]

I am reading Roger Lewin's principles of human evolution, this is the first book on evolutionary biology I've read, and I've grasped a lot of the concepts learned so far. Natural selection, from the Darwins point of view, actively preserves beneficial traits, it does not weed out bad ones. The neutral theory of molecular evolution says that evolutionary change is due to genetic drift, when a population favors specific genes and alleles not due to an outside force like predators or environmental change (natural selection) but due to mutations or lack/excess reproduction. How do the two go together? Is the neutral theory of molecular evolution purely on the molecular level? I am confused on this, and who is right? The Darwinists, or the proponents of the NTOME? My knowledge of biology solely comes from one watered down honors course I took in my freshman year of high school (I'm now a senior and taking ap bio this year).

 

[el es]

I don't think it is a case of either/or.

"Neutral theory does not deny the occurrence of natural selection."

https://en.wikipedia.org/wiki/Neutral_theory_of_molecular_evolution

It may be that genetic variation and drift are necessary for natural selection to work.

http://phys.org/news/2015-02-evolution-darwin-finches-beaks.html

 

[spidergoat]

I am reading Roger Lewin's principles of human evolution, this is the first book on evolutionary biology I've read, and I've grasped a lot of the concepts learned so far. Natural selection, from the Darwins point of view, actively preserves beneficial traits, it does not weed out bad ones. The neutral theory of molecular evolution says that evolutionary change is due to genetic drift, when a population favors specific genes and alleles not due to an outside force like predators or environmental change (natural selection) but due to mutations or lack/excess reproduction. How do the two go together? Is the neutral theory of molecular evolution purely on the molecular level? I am confused on this, and who is right? The Darwinists, or the proponents of the NTOME? My knowledge of biology solely comes from one watered down honors course I took in my freshman year of high school (I'm now a senior and taking ap bio this year).

I'm guessing that both things occur, genetic drift and natural selection. Of course, preserving beneficial traits is the same thing as weeding out bad ones. And most mutations are neutral in effect.

 

[iceaura]

Genetic drift is part of a mechanism of selection.

Natural selection, from the Darwins point of view, actively preserves beneficial traits, it does not weed out bad ones.

It's the other way around. Natural selection weeds, and partly by accident - over time it will probably tend to weed out bad traits, but it's a probability and a tendency only. It preserves nothing - it will kill off entire species, and all their traits good or bad, without even noticing.

So let me put you this way , forget the carnivorous, would I be correct if say herbivorous

Most animals will eat meat under routine circumstances, and most herbivores routinely take in small animals with their diet. If you raise cows in a barn, for example, you have to supplement their hay and grass and so forth with protein or they won't thrive - in a field they would be eating lots of insects and the like. Deer eat birds and fish sometimes, elephants eat entire nests of birds,

Many insects build cannibalism into their normal life stages, many larger animals with expensive young have a stage in their development when the mother "decides" whether the resources and prospects are adequate and either resorbs or outright eats the progeny if they aren't.

 

[exchemist]

I'm guessing that both things occur, genetic drift and natural selection. Of course, preserving beneficial traits is the same thing as weeding out bad ones. And most mutations are neutral in effect.

That was also my understanding, viz. that genetic drift, horizontal gene transfer and other processes occur alongside the classical preferential inheritance of traits favoured by natural selection.

I do not see any reason to think that the one would exclude the other. I think it is just that we are gradually learning the whole thing is more subtle and complex than a simple inheritance/selection picture. But I'm not a biologist so I'd be very interested to see a contribution from someone more qualified.

 

[The Great Red Dragon]

That was also my understanding, viz. that genetic drift, horizontal gene transfer and other processes occur alongside the classical preferential inheritance of traits favoured by natural selection.

I do not see any reason to think that the one would exclude the other. I think it is just that we are gradually learning the whole thing is more subtle and complex than a simple inheritance/selection picture. But I'm not a biologist so I'd be very interested to see a contribution from someone more qualified.

I think you're right. After sleeping on it and thinking it through this morning it make perfect sense that they go hand in hand with one another. If the mutation is only occurring on the molecular level, natural selection can't affect it, this means that genetic drift and HGT are the only way in which the gene can become widespread in the population. I am new to these concepts and am speculating at this point.

 

[exchemist]

I think you're right. After sleeping on it and thinking it through this morning it make perfect sense that they go hand in hand with one another. If the mutation is only occurring on the molecular level, natural selection can't affect it, this means that genetic drift and HGT are the only way in which the gene can become widespread in the population. I am new to these concepts and am speculating at this point.

Well, I would have thought that a molecular level change could have consequences for survival and, if it did, it would get selected for or against.

My understanding is that neutral molecular changes means those changes that do not have such consequences, and thus can proliferate within a population of organisms without affecting reproductive success. Presumably if the selection pressures on the organism then alter (environment changes, predation or competition from other species, etc) such that some of these molecular changes start to be relevant to reproductive success, then natural selection would start to operate on them.

 

[iceaura]

That was also my understanding, viz. that genetic drift, horizontal gene transfer and other processes occur alongside the classical preferential inheritance of traits favoured by natural selection.

Genetic drift is a type of natural selection. Horizontal gene transfer is a mode of reproduction.

Reproduction of the gene. Drift of the gene. Evolution of the genetic code.

 

[exchemist]

Genetic drift is a type of natural selection. Horizontal gene transfer is a mode of reproduction.

Reproduction of the gene. Drift of the gene. Evolution of the genetic code.

That does not sound right to me: https://en.wikipedia.org/wiki/Horizontal_gene_transfer

As I read this, transfer of individual genes between organisms is a means by which traits (such as antibiotic resistance) are transferred from one organism to another one, without reproduction being involved.