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From Talk:Genetic drift
Not to presume that others aren't bored stiff and gone on a hiatus by now, but since this came to my mind, I'll post it now: In an earlier version of the article, I thought to do some explaining by way of a naturalistic example. I decided it was too long winded, but if people want examples, and if we keep the examples section I suggested, perhaps a piece of text along the following lines would be useful:
"Consider the quasi-realistic example of a hypothetical hoof-related gene of wildebeests, in which a rare allele confers a superior propulsion when treading water. Suppose that each year half of a herd drowns in crossing the roaring river that separates its summer and winter grazing areas. Who survives depends only partly on ability and partly on luck--whether a stampeding animal's neighbors in the water are prone to panic, for example. Nevertheless, carriers of the rare hoof allele do better when given a fighting chance, so they drown less often on average. As the years pass, the allele becomes more common. This is a case of natural selection.
"Consider now the roughly 50,000 other genes in the wildebeest genome for which there exist multiple alleles...."
I don't know how ecologically or "populo-genetically" sound an example this is (I do know from a nature video that wildebeests migrate to breeding grounds annually, that they may cross a big river to do so, and that many die in the river) so maybe someone can propose something better. What I like about the above is that it names a specific animal that I think will engage people's interest, it's explicit and naturalistic, it's oriented toward action happening on the human scale, it's told as a narrative and (to the extent it isn't confused about any of them) it makes the concepts stark 168... 16:18 21 May 2003 (UTC)
I reverted the article because of two problems which I have been reviewing with 168. In his comments on this page he writes:
which once again reveals his confusion. No one said that lifespan is irrelevant to allele frequency. Changes in allele frequence is one simple way of defining evolution, and clearly, lifespan is relevant to evolution. The question is not whether lifespan is relevant to evolution, but whether it is relevant to genetic drift. At this point I wonder whether 168 believes that drift is evolution, and not just one factor in evolution. According to the modern synthesis, drift is only one factor (sexual selection and natural selection are two other forces, and there are others). So to answer 168's question, lifespan may be relevant to drift, it may not be -- it depends. Accidental death is relevant to drift, but death as a result of selective forces is not. So the article must make clear that we are talking about accidental death (hence my revert). Slrubenstein
168 also continues to question the importance of HW, and where it should come in the article. Clearly, as Dobzhansky and Mayr make clear, HW is a baseline for any discussion of drift. In a way, drift is any deviation from a HW equilibrium. So before one discusses drift, one must explain the HW equilibrium (hence my revert). Slrubenstein
Here we go again. An excerpt from the above discussion:
Although I appreciate 168's efforts at clarification, it does not bear on my point. I did not assert that lifespan is irrelevant unless if influences the number of offspring. (Let's leave aside the fact that offspring are relevant, since evolution in any form involves changes in gene frequencies from one generation to the next; offspring is how alleles are carried into the next generation, and the number of offspring is one factor in fitness.) What I asserted is that lifespan is irrelevant if it is determined by fitness/natural selection, rather than chance. If someone dies at any age because of natural selection, the consequent change in the allele frequencies in the next generation are not an example of drift. If someone dies at any age because of an accident, and if the population is relatively small, the consequent changes in allele frequencies in the next generation are an example of drift. Slrubenstein
Another example from above:
Hmmm. Your point is that "it can't be right to describe it as the essence or the be-all...?" That is funny, because I never said it was the be-all and end-all, what I did say is that it is a baseline that needs to be up front. The reason I said it needs to be up front was that I was responding to your point, "HWE didn't belong high up in the article." You see, that is what I thought your point was. I thought that was your point because you said "My point was..." Can you see how I get confused when I try to discuss these matters with you? You make a point -- you write "My point is that HWE didn't belong high up..." and I explain why I do think it belongs high up and you say tell me I am not responding to your point! But HWE is the baseline, and belongs up front for good reason. I take very seriously your desire to communicate these issues clearly to a lay audience. So let us strive to explain them as clearly as possible. This may take more concrete examples, or more explanation -- fine. But let us not distort the science. Slrubenstein
I addressed this in my remarks preceeding "This shows that one need not explain HWE before explaining drift" above. 168... 19:39 21 May 2003 (UTC)
![]() | This page is an archive of past discussions. Do not edit the contents of this page. If you wish to start a new discussion or revive an old one, please do so on the current talk page. |
From Talk:Genetic drift
Not to presume that others aren't bored stiff and gone on a hiatus by now, but since this came to my mind, I'll post it now: In an earlier version of the article, I thought to do some explaining by way of a naturalistic example. I decided it was too long winded, but if people want examples, and if we keep the examples section I suggested, perhaps a piece of text along the following lines would be useful:
"Consider the quasi-realistic example of a hypothetical hoof-related gene of wildebeests, in which a rare allele confers a superior propulsion when treading water. Suppose that each year half of a herd drowns in crossing the roaring river that separates its summer and winter grazing areas. Who survives depends only partly on ability and partly on luck--whether a stampeding animal's neighbors in the water are prone to panic, for example. Nevertheless, carriers of the rare hoof allele do better when given a fighting chance, so they drown less often on average. As the years pass, the allele becomes more common. This is a case of natural selection.
"Consider now the roughly 50,000 other genes in the wildebeest genome for which there exist multiple alleles...."
I don't know how ecologically or "populo-genetically" sound an example this is (I do know from a nature video that wildebeests migrate to breeding grounds annually, that they may cross a big river to do so, and that many die in the river) so maybe someone can propose something better. What I like about the above is that it names a specific animal that I think will engage people's interest, it's explicit and naturalistic, it's oriented toward action happening on the human scale, it's told as a narrative and (to the extent it isn't confused about any of them) it makes the concepts stark 168... 16:18 21 May 2003 (UTC)
I reverted the article because of two problems which I have been reviewing with 168. In his comments on this page he writes:
which once again reveals his confusion. No one said that lifespan is irrelevant to allele frequency. Changes in allele frequence is one simple way of defining evolution, and clearly, lifespan is relevant to evolution. The question is not whether lifespan is relevant to evolution, but whether it is relevant to genetic drift. At this point I wonder whether 168 believes that drift is evolution, and not just one factor in evolution. According to the modern synthesis, drift is only one factor (sexual selection and natural selection are two other forces, and there are others). So to answer 168's question, lifespan may be relevant to drift, it may not be -- it depends. Accidental death is relevant to drift, but death as a result of selective forces is not. So the article must make clear that we are talking about accidental death (hence my revert). Slrubenstein
168 also continues to question the importance of HW, and where it should come in the article. Clearly, as Dobzhansky and Mayr make clear, HW is a baseline for any discussion of drift. In a way, drift is any deviation from a HW equilibrium. So before one discusses drift, one must explain the HW equilibrium (hence my revert). Slrubenstein
Here we go again. An excerpt from the above discussion:
Although I appreciate 168's efforts at clarification, it does not bear on my point. I did not assert that lifespan is irrelevant unless if influences the number of offspring. (Let's leave aside the fact that offspring are relevant, since evolution in any form involves changes in gene frequencies from one generation to the next; offspring is how alleles are carried into the next generation, and the number of offspring is one factor in fitness.) What I asserted is that lifespan is irrelevant if it is determined by fitness/natural selection, rather than chance. If someone dies at any age because of natural selection, the consequent change in the allele frequencies in the next generation are not an example of drift. If someone dies at any age because of an accident, and if the population is relatively small, the consequent changes in allele frequencies in the next generation are an example of drift. Slrubenstein
Another example from above:
Hmmm. Your point is that "it can't be right to describe it as the essence or the be-all...?" That is funny, because I never said it was the be-all and end-all, what I did say is that it is a baseline that needs to be up front. The reason I said it needs to be up front was that I was responding to your point, "HWE didn't belong high up in the article." You see, that is what I thought your point was. I thought that was your point because you said "My point was..." Can you see how I get confused when I try to discuss these matters with you? You make a point -- you write "My point is that HWE didn't belong high up..." and I explain why I do think it belongs high up and you say tell me I am not responding to your point! But HWE is the baseline, and belongs up front for good reason. I take very seriously your desire to communicate these issues clearly to a lay audience. So let us strive to explain them as clearly as possible. This may take more concrete examples, or more explanation -- fine. But let us not distort the science. Slrubenstein
I addressed this in my remarks preceeding "This shows that one need not explain HWE before explaining drift" above. 168... 19:39 21 May 2003 (UTC)