tag:blogger.com,1999:blog-37148773.post1467349199100127267..comments2024-03-27T14:50:47.345-04:00Comments on <center>Sandwalk</center>: Why does the human population carry an allele that increases the risk of Alzheimer's?Larry Moranhttp://www.blogger.com/profile/05756598746605455848noreply@blogger.comBlogger36125tag:blogger.com,1999:blog-37148773.post-56693597488782189222017-01-30T11:30:07.492-05:002017-01-30T11:30:07.492-05:00Here is access to an oldie but goodie by George C....Here is access to an oldie but goodie by George C. Williams on the general situation of the evolution of senescence. Several of the issues raised seem relevant.<br />http://sageke.sciencemag.org/cgi/content/abstract/2001/1/cp13W. Bensonhttps://www.blogger.com/profile/11019350102074238654noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-15063893708146301942017-01-25T16:59:08.940-05:002017-01-25T16:59:08.940-05:00Pleiotropy is a good one, was thinking about that ...Pleiotropy is a good one, was thinking about that too. If it deleterious but shows up after reproduction, it wouldn't be subjected to negative selection hence was not weeded out.Imolahttps://www.blogger.com/profile/08192905631353037500noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-58060465035090512772017-01-25T07:30:08.450-05:002017-01-25T07:30:08.450-05:00@Ed says,
Until about thirty years ago, most peop...@Ed says,<br /><br /><i>Until about thirty years ago, most people rarely ate modern 'western style diets.'"</i><br /><br />Thirty years ago is 1987. I don't know what you mean by "Western type" foods but my eating habits haven't changed very much since I was a teenager in the 1960s. I don't see any big change that occurred in the late 1980s. Larry Moranhttps://www.blogger.com/profile/05756598746605455848noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-45448265663888517712017-01-25T05:47:48.950-05:002017-01-25T05:47:48.950-05:00I used to work in a research project on cardiovasc...I used to work in a research project on cardiovascular disease using ApoE3 knock out mice. If you fed the mice normal rodent chow, cholesterol and fat contents of blood remained at normal levels. If you started to feed them 'western type foods' cholesterol and fat in blood would sky rocket. In the long run mice most mice would get cardiovascular issues related to the high fat/ cholesterol.<br /><br />This sounds to me to be a combination of environment and prevalence of the gene(s) which lead to Alzheimer. Until about 30 years ago, most people rarely ate modern 'western style diets' ie high fat, sugar. And people are getting older due to better health care. <br /><br />But I have to agree, these diseases occur years, even decades, after people reproduce. And don't forget ApoE has an important function in normal catabolism.<br /><br />It seems ApoE4 is most common in Nigeria, but since few people there have access to western style food, Alzheimers is rare.Edhttps://www.blogger.com/profile/15924368353226400878noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-49280647654840724942017-01-24T20:44:55.140-05:002017-01-24T20:44:55.140-05:00There are several genetic diseases (syndromes) tha...There are several genetic diseases (syndromes) that are not acted on to any great extent by selection. Marfans runs in my family and I have the genetic markers. It is a connective tissue disorder who's most lethal symptoms are heart valve problems and aneurisms. But, since they don't usually present themselves until the person is in their 50s, it doesn't prevent me from reproducing. William Spearshakehttps://www.blogger.com/profile/09354659259971103985noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-7620189516611515612017-01-24T19:24:25.422-05:002017-01-24T19:24:25.422-05:00No one mentions possible pleiotropy or linkage?No one mentions possible pleiotropy or linkage?Bjørn Østmanhttps://www.blogger.com/profile/08859177313382114917noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-61219452695642020342017-01-24T18:38:26.323-05:002017-01-24T18:38:26.323-05:00Scan error. I beg your pardon. Thanks for the corr...Scan error. I beg your pardon. Thanks for the correction.txpiperhttps://www.blogger.com/profile/03645156881353741058noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-88187706786213808232017-01-24T18:19:06.490-05:002017-01-24T18:19:06.490-05:00Your positition seems to be either E4 is an adapta...Your positition seems to be either E4 is an adaptation to brain parasites, caused by natural selection for the reproductive advantage of neurologically healthy parents and grand-parents to the offspring *or* for its opposite, natural selection in humans for the alleles that are replacing this vestige of ape neurology. Perhaps this is not literally perfect, but your position is that particular DNA is not junk. This seems to me to be wholly unfounded. Natural selection is not powerful enough to optimize traits with marginal or variable effects on reproductive success in the face of mutation, drift, etc.<br /><br />Therefore I am unrepentant about equating adaptationists of Yong's sort with creationists, which is the topic at hand after all. Your version where natural selection hasn't finished perfecting apolipoprotein in the human brain, sorry, no, it's a possibility. But there's no evidence for it that I know of. S Johnsonhttps://www.blogger.com/profile/11610068751705809284noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-53234423834435558592017-01-24T16:04:34.761-05:002017-01-24T16:04:34.761-05:00@John: I overstated. The McIntosh et al. (2012) p...@John: I overstated. The McIntosh et al. (2012) paper shows all chimps in their sample having an E4-like allele. For other apes it shows an allele like that but the samples are too small to assess whether these are fixed.<br />Joe Felsensteinhttps://www.blogger.com/profile/06359126552631140000noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-44273656578282275322017-01-24T16:01:20.518-05:002017-01-24T16:01:20.518-05:00Evolutionary biology does not predict perfect adap...Evolutionary biology does <i>not</i> predict perfect adaptation. It is the imperfections that provide one source of evidence that evolution produced the adaptations. On your side the argument is obviously <i>for</i> perfection since "God don't make no junk".Joe Felsensteinhttps://www.blogger.com/profile/06359126552631140000noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-7424409883134645142017-01-24T13:54:39.240-05:002017-01-24T13:54:39.240-05:00In fact, studies of polymorphism of Apoliliprotein...<i>In fact, studies of polymorphism of Apoliliprotein loci in apes show (McIntosh et al., PLoS One, 2012) that apes are fixed for sequences related to the E4 allele.</i><br /><br />When you say "apes" are you referring to <i>Pan troglodytes</i> only, or is there some other paper I haven't found that assays lots of species?John Harshmanhttps://www.blogger.com/profile/04478895397136729867noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-62969563583185079162017-01-24T12:08:30.214-05:002017-01-24T12:08:30.214-05:00Ah, after this elementary reading comprehension fa...Ah, after this elementary reading comprehension fail, some things begin to become clearer.judmarchttps://www.blogger.com/profile/03111006189037693272noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-29741906803270902082017-01-24T11:55:48.592-05:002017-01-24T11:55:48.592-05:00He doesn't, at least not in that sentence. He ...He doesn't, at least not in that sentence. He is referring to the species, not every individual.SRMhttps://www.blogger.com/profile/07299706694667706149noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-84302165853305925852017-01-24T11:54:24.089-05:002017-01-24T11:54:24.089-05:00It doesn't say that we all have it. Check the ...It doesn't say that we all have it. Check the sentence: "The fact that we have it at all" does not mean "the fact that we all have it."Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-37148773.post-34131648344733669242017-01-24T11:19:05.526-05:002017-01-24T11:19:05.526-05:00Thanks jaxkayaker.
Actually I know what a z-score ...Thanks jaxkayaker.<br />Actually I know what a z-score is.<br />But I have no Idea, how they actually calculated their mean(s). For each Eosinophil count a new one or a global one? <br /><br />Best Michael <br />Thx again,<br />MichaelAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-37148773.post-35411951581670876312017-01-24T10:35:49.621-05:002017-01-24T10:35:49.621-05:00A z-score is a measure of how many standard deviat...A z-score is a measure of how many standard deviations away from the arithmetic mean (average) an observation is. (Observed value minus mean value) divided by the standard deviation is the z-score. <br /><br />-jaxkayakerKeithhttps://www.blogger.com/profile/03141027405807111565noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-62105195960920078242017-01-24T09:45:48.270-05:002017-01-24T09:45:48.270-05:00“ “You’d have thought that natural selection would...<i>“ “You’d have thought that natural selection would have weeded out ApoE4 a long time ago. The fact that we have it at all is a little bizarre.” “</i><br /><br />Why does he say we all have it?<br /><br /><b>Common Alzheimer’s gene APOE4 raises risk for women but not men</b><br /><i>“APOE4 is the riskiest known Alzheimer’s gene variant…It’s riskiest because it is so common. As many as 1 in 5 people possess APOE4……….Researchers don’t yet know exactly how the allele does its work, but a 2012 review declared that a person with one copy of APOE4 has three times the risk of LOAD as a noncarrier. Two copies increase the risk by about 12 times.”</i><br />https://www.geneticliteracyproject.org/2014/04/22/common-alzheimers-gene-apoe4-raises-risk-for-women-but-not-men/ <br />txpiperhttps://www.blogger.com/profile/03645156881353741058noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-77170995058394134172017-01-24T08:48:04.039-05:002017-01-24T08:48:04.039-05:00The observation that E4 is fixed in apes, but not ...The observation that E4 is fixed in apes, but not in humans, implies (in the adaptationist perspective at any rate,) that E4 is undergoing negative selection is directly opposed to the Yong article. The thing is, the question of whether this negative selection pressure actually exists at all is still left unexamined. Both positions, E4 is adaptive and E4 isn't adaptive but a mere vestige, are equally unsupported. S Johnsonhttps://www.blogger.com/profile/11610068751705809284noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-66540936707572026232017-01-24T08:34:44.854-05:002017-01-24T08:34:44.854-05:00You do not quote a creationist argument. Perfectio...You do not quote a creationist argument. Perfection of design by natural selection is not really distinguishable from perfection of design from a Creator, which means it's those who presume perfection who are making the creationist arguments. You have everything upside down.S Johnsonhttps://www.blogger.com/profile/11610068751705809284noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-50782026909907674712017-01-24T07:12:43.996-05:002017-01-24T07:12:43.996-05:00Thanks, Joe re fixation - I hadn't seen your c...Thanks, Joe re fixation - I hadn't seen your comment while I was writing mine.judmarchttps://www.blogger.com/profile/03111006189037693272noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-44578888875127401162017-01-24T07:09:32.311-05:002017-01-24T07:09:32.311-05:00Human societies/populations and their survival dur...Human societies/populations and their survival during evolutionary time spans is not a subject we know everything about quite yet. I can fault the article for not mentioning the default explanation (as long as we can tell the allele involved isn't subjected to strong negative or positive selection - anyone know?), but not for following scientists and their curiosity regarding more or less plausible adaptationist explanations. I thought the research was interesting.judmarchttps://www.blogger.com/profile/03111006189037693272noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-16686702008036867912017-01-24T07:03:14.347-05:002017-01-24T07:03:14.347-05:00Adaptationism has the great advantage of adhering ...<i>Adaptationism has the great advantage of adhering to the common observation that "God don't make no junk." </i><br /><br />Then how do we account for creationist arguments like yours?Joe Felsensteinhttps://www.blogger.com/profile/06359126552631140000noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-56312494656936830452017-01-24T07:01:28.268-05:002017-01-24T07:01:28.268-05:00I agree with Larry that selection to avoid Alzheim...I agree with Larry that selection to avoid Alzheimer's disease will be weak, especially since basically all reproduction occurs before there is much risk of Alzheimer's disease. And yes, effective population sizes in the human lineage were small. Note, though, that E4 is not fixed in humans. <br /><br />In fact, studies of polymorphism of Apoliliprotein loci in apes show (McIntosh et al., PLoS One, 2012) that apes are fixed for sequences related to the E4 allele. That at least raises the possibility that it is the other alleles that have been favored in humans. Larry should be interested in this issue.Joe Felsensteinhttps://www.blogger.com/profile/06359126552631140000noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-46530887690393114642017-01-24T06:55:29.513-05:002017-01-24T06:55:29.513-05:00The first author of the study published 16 papers ...The first author of the study published 16 papers (Pubmed) with corelational data on the 'Amazonian forager-horticulturalists' (published in between 2012 and 2016) with 8 as a first author). Am I jealous?<br /><br />The correlations tested involve (taken from the titles):<br /> <br />-parasite burden, ApoE alleles and cognition<br />-parasite infection with cardiovascular disease and type 2 diabetes<br />-parasite infection with Depression as sickness behavior<br />-immune function (largely parasite related) and age-related differences forager-horticulturalists, US and Europeans<br />-parasite burden and metabolism rates<br /><br />-testosterone & parasite infection with immune function <br />-testosterone levels with physical competition<br />-testosterone levels (and cortisol) with successful hunting<br />-testosterone levels (age dependent) with horticultural activity<br />-testosterone levels (male) with cognitive performance<br />-testosterone and oxitocin levels when hunters come home<br /><br />-Cortisol with political influence<br /><br />-fertility and mineral density among adult women<br />-fertility and parasite infection<br /> <br />-No Sex or Age Difference in Dead-Reckoning Ability among Tsimane Forager-Horticulturalists.<br />-An epigenetic clock analysis of race/ethnicity, sex, and coronary heart disease.<br /><br />I had a look in the paper and I don't understand the method they used to compare the cognitive capabilities of the groups tested. Maybe someone with access & more statistical knowledge can help me out? It might turn out to be an interesting lesson in statistics & correlations.<br /><br />In Figure 2 'z Scan' they plot the z-scores for the cognitive tests for the different genotypes against the parasitic load (measured by Eosinophil count;) no data point are given. <br />I don't understand how the z-scores (?) are calculated and how the performance in the tests is actually calculated.<br /><br />The naive eye would interpret the graph as follows: having the E4 allele your cognition gets better and better the more parasites you have.<br /><br /><br />Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-37148773.post-44975990629077798482017-01-24T06:53:50.626-05:002017-01-24T06:53:50.626-05:00Yes, of course,Yes, of course,Larry Moranhttps://www.blogger.com/profile/05756598746605455848noreply@blogger.com