"Natural selection requires three things."

[lukeprog]

Jerry Coyne says that the point about natural selection requiring three things (heritability, variation, selection) was discussed by Dawkins in The Selfish Gene. I skimmed that book and couldn't find it. Does anyone know where Dawkins discusses this point? I think it was Dawkins' discussion that finally made sense of evolution to me after being raised with a creationist education, but now I can't find the passage I'm thinking of.

[Halucigenia]

Jerry Coyne says that the point about natural selection requiring three things

Not quite true; Evolution requires at least these three things (not to the exclusion of other processes also being involved).

 

(heritability, variation, selection)

Natural selection being a process of selection.

I don't want to diss Jerry Coyne but the wording is a little sloppy. And in your post you do miss out the vital word - evolution.

 

was discussed by Dawkins in The Selfish Gene. I skimmed that book and couldn't find it. Does anyone know where Dawkins discusses this point?

I am sure that it will be the basis of most of his book as it is the basis of the theory of evolution generally.

 

I think it was Dawkins' discussion that finally made sense of evolution to me after being raised with a creationist education, but now I can't find the passage I'm thinking of.

I will try and find a reference but I am not sure what the point of finding it would be.

 

I think that you are actually missing Jerry Coynes point in that link. (Thanks for the link, it is very interesting.)

 

The point is that in the example evolution may not necessarily be using the genes as the heritable component. Instead Its based on changes in the presence of symbiotic bacteria that protect a species from parasites

However, I dont think that Jerry Coyne is saying that Richard Dawkins Selfish gene metaphor is wrong, simply that evolutionary processes could operate without genes. However, it is presumably the genes of the bacteria that are being pressed in to service in this instance that assist in enabling the genes of the fly to be inherited so even if its evolution without the genes of the host being involved the genes of the symbiont are actually being used. It would simply be a case of the genes of host and symbiont co-operating in the selfish action that they both become replicated successfully in the presence of the parasitic nematode.

 

In fact I am sure that Richard Dawkins make the exact same point it could even be in The Selfish Gene where he states that even genes of separate organisms can co-operate to achieve their selfish end of being replicated. He also gives an example, as far as I can remember, where the genes of the co-operating organism have to be propagated in the gametic cell line of the host organism i.e. the eggs, but it is a different example organism that he uses.

I will have to check the reference when I get the chance.

Edited November 9, 2011 by Halucigenia

[Halucigenia]

I found the bit in The Selfish Gene that I was talking about. It's in Chapter 12 - Nice Guys Finish First.

Look at what can happen when parasite genes and host genes do share a common exit. Wood-boring ambrosia beetles (of the species Xyleborusferrugineus)are parasitized by bacteria that not only live in their host's body but also use the host's eggs as their transport into a new host. The genes of such parasites therefore stand to gain from almost exactly the same future circumstances as the genes of their host. The two sets of genes can be expected to 'pull together' for just the same reasons as all the genes of one individual organism normally pull together. It is irrelevant that some of them happen to be 'beetle genes', while others happen to be 'bacterial genes'. Both sets of genes are 'interested' in beetle survival and the propagation of beetle eggs, because both 'see' beetle eggs as their passport to the future. So the bacterial genes share a common destiny with their host's genes, and in my interpretation we should expect the bacteria to cooperate with their beetles in all aspects of life.

 

In the Foreword Dawkins says this:-

Chimp and human, lizard and fungus, we have all evolved over some three billion years by a process known as natural selection. Within each species some individuals leave more surviving offspring than others, so that the inheritable traits (genes) of the reproductively successful become more numerous in the next generation. This is natural selection: then non random differential reproduction of genes. Natural selection has built us, and it is natural selection we must understand if we are to comprehend our own identities.

It alludes to heritability "inheritable traits" and variation "of the reproductively successful" - suggesting that there is variation as some are reproductively unsuccessful, and selection "become more numerous in the next generation". So he is describing evolution in terms of variation heritability and selection.

 

I can't see anywhere in the text that this is spelled out more explicitly but it runs all through the book.

 

I hope that this helps.