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Author Topic:   Human Evolution - Speciation
Mammuthus
Member (Idle past 6465 days)
Posts: 3085
From: Munich, Germany
Joined: 08-09-2002


Message 16 of 39 (157905)
11-10-2004 8:46 AM
Reply to: Message 13 by Dr Jack
11-10-2004 6:54 AM


Here is a reference
Am J Hum Genet. 1991 Apr;48(4):677-81. Related Articles, Links
Alcohol and aldehyde dehydrogenase genotypes and alcoholism in Chinese men.
Thomasson HR, Edenberg HJ, Crabb DW, Mai XL, Jerome RE, Li TK, Wang SP, Lin YT, Lu RB, Yin SJ.
Department of Medicine, Indiana University School of Medicine, Indianapolis 46202-5121.
The liver enzymes alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH), which are responsible for the oxidative metabolism of ethanol, are polymorphic in humans. An allele encoding an inactive form of the mitochondrial ALDH2 is known to reduce the likelihood of alcoholism in Japanese. We hypothesized that the polymorphisms of both ALDH and ADH modify the predisposition to development of alcoholism. Therefore, we determined the genotypes of the ADH2, ADH3, and ALDH2 loci of alcoholic and nonalcoholic Chinese men living in Taiwan, using leukocyte DNA amplified by the PCR and allele-specific oligonucleotides. The alcoholics had significantly lower frequencies of the ADH2*2, ADH3*1, and ALDH2*2 alleles than did the nonalcoholics, suggesting that genetic variation in both ADH and ALDH, by modulating the rate of metabolism of ethanol and acetaldehyde, influences drinking behavior and the risk of developing alcoholism.

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Dr Jack
Member
Posts: 3514
From: Immigrant in the land of Deutsch
Joined: 07-14-2003
Member Rating: 8.2


Message 17 of 39 (157909)
11-10-2004 8:59 AM
Reply to: Message 16 by Mammuthus
11-10-2004 8:46 AM


Re: Here is a reference
Sweet. Thanks, Mammuthus.

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Dr Jack
Member
Posts: 3514
From: Immigrant in the land of Deutsch
Joined: 07-14-2003
Member Rating: 8.2


Message 18 of 39 (157911)
11-10-2004 9:07 AM
Reply to: Message 14 by wormjitsu
11-10-2004 7:59 AM


Re: exercise and genetics
Anyways, given this example...I'm curious if high levels of physical exertion throughout a lifetime from generation to generation could potentially mutate genetics.
It seems to me you aren't clear on your terms. Continuous consumption of alcohol in Europeans did not mutate their genes; it selected for people with a higher alcohol tolerance - presumably because they were more able to function while drinking, and less likely to consume other, less safe, liquids thus increasing both their likelyhood of surviving to adulthood and their ability to support more children.
Anyways, given this example...I'm curious if high levels of physical exertion throughout a lifetime from generation to generation could potentially mutate genetics.
In short, no. Unless that physical exertion was directed towards a goal that increased (at least one of) their likelyhood of living to reproductive age, their ability to attract mates and their ability to support children (for example, if they were hunted by fierce predators faster runners could be more likely to survive, women could prefer more athletic men or among active hunters there could be a selection pressure for higher endurance and faster runners, respectively).

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Coragyps
Member (Idle past 725 days)
Posts: 5553
From: Snyder, Texas, USA
Joined: 11-12-2002


Message 19 of 39 (157920)
11-10-2004 9:26 AM
Reply to: Message 15 by contracycle
11-10-2004 8:32 AM


Does anyone know if a timescale can be established for when this mutation was introduced?
I'll speculate that it was before Asians colonized the Americas. Native Americans are rather notoriously alcohol-intolerant: whether their genetic basis for this is the same as that in the Chinese Mammuthus cites I don't know. I'll bet it's published, though.

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Mammuthus
Member (Idle past 6465 days)
Posts: 3085
From: Munich, Germany
Joined: 08-09-2002


Message 20 of 39 (157935)
11-10-2004 9:54 AM
Reply to: Message 19 by Coragyps
11-10-2004 9:26 AM


Looked up a few more papers. It seems (though maybe someone will find newer info that I missed) that the Asian and native American alcohol intolerance differs genetically. But since both alcohol tolerant and intolerant genotypes both exist in Asian populations, it could mean that native Americans derived from an alcohol tolerant group and the flushing reaction to alcohol is a de novo mutation.
J Stud Alcohol. 1999 Mar;60(2):149-58. Related Articles, Links
An examination of ALDH2 genotypes, alcohol metabolism and the flushing response in Native Americans.
Gill K, Eagle Elk M, Liu Y, Deitrich RA.
Alcohol Research Center, Department of Pharmacology, University of Colorado Health Sciences Center, Denver, USA.
OBJECTIVE: The study was designed to examine the relationship between aldehyde dehydrogenase (ALDH2) genotype and the flushing response in a population of Native Americans. METHOD: Objective measures of the flushing response were obtained by monitoring skin temperature, heart rate, blood pressure, as well as blood alcohol concentrations, in flushing and nonflushing Native Americans (n = 105) as well as in Oriental (n = 15) and white (n = 15) control subjects following a dose of alcohol (0.2 or 0.4 gm/kg). ALDH genotypes were determined via polymerase chain reaction followed by hybridization to 32P or biotin-labeled allele-specific oligonucleotide probes. RESULTS: There were no ALDH2 mutations detectable in Native Americans reporting the flushing response, nor any objective evidence of an Oriental-like response to alcohol. The rate of alcohol metabolism was shown to be the same among whites, Native flushers and Native nonflushers. CONCLUSIONS: The results demonstrate that the flushing reaction experienced by Native Americans appears to be milder and less unpleasant than the "Oriental" flushing reaction, with little effect on drinking frequency and amount. In addition, the flushing is not mediated by the ALDH2 mutation or elevated blood acetaldehyde. A critical analysis of the discrepancies in the literature regarding alcohol metabolism in Native Americans is provided.
Hum Hered. 1993 Mar-Apr;43(2):116-20. Related Articles, Links
Absence of the atypical mitochondrial aldehyde dehydrogenase (ALDH2) isozyme in Saskatchewan Cree Indians.
Dyck LE.
Department of Psychiatry, University of Saskatchewan, Saskatoon, Canada.
Three methods were employed to assess whether human volunteers (Caucasian, Asian or Cree Indian) possessed the typical or atypical mitochondrial aldehyde dehydrogenase (ALDH2) isozyme. These methods were: (1) questioning individuals about facial flushing responses following alcohol consumption; (2) application of the ethanol skin patch test, and (3) direct analysis using isoelectric focusing and activity staining of ALDH activity in hair root samples. The results from the three methods were in good agreement and revealed that only the typical ALDH2 isozyme was expressed in Saskatchewan Cree Indians. In agreement with previous reports, the typical ALDH2 was expressed in the Caucasian group of subjects, while both the typical and atypical forms were expressed in the Asian subjects.
Behav Genet. 1995 Jan;25(1):59-65. Related Articles, Links
Alcohol consumption by orientals in North America is predicted largely by a single gene.
Tu GC, Israel Y.
Primary Mechanisms Department, University of Toronto, Canada.
Orientals consume significantly less alcohol, and show a lower prevalence of alcohol abuse and dependence, than Caucasians. Sociological theories propose that this difference is due mainly to cultural factors. Physiological theories have suggested that the flushing reaction experienced by some Orientals serves as a deterrent to ethanol consumption. The flushing reaction is observed mainly in individuals who possess a mutation in the high-affinity aldehyde dehydrogenase (ALDH2) which renders the enzyme inactive. However, the tendency to flush correlates poorly with alcohol consumption, thus casting doubt on the physiological interpretations. The present study investigates the influence of the ALDH2 allele and of acculturation in North America on alcohol consumption by Orientals born in Canada or the United States. Oriental males carrying the inactive ALDH2(-) allele drink two-thirds less alcohol (6.1 +/- 1.5 vs. 18.2 +/- 2.8 drinks/4 weeks; p < 0.001), show one-third the prevalence of binge drinking (15.2 vs. 42.2%; p < 0.01), and are three times more likely to be abstainers (39.4 vs. 13.3%; p < 0.01) than Oriental ALDH2(+) males carrying the gene for the active enzyme. There were no significant differences in binge drinking or abstinence rates between ALDH2(+) Orientals and Caucasian males. Acculturation in North American society accounted for only 7-11% of the variance in overall consumption (p < 0.02). It is concluded that a single mutation in the high-affinity aldehyde dehydrogenase (ALDH2) gene predicts two-thirds of the alcohol consumption and excessive alcohol use by Oriental males born in North America.

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Loudmouth
Inactive Member


Message 21 of 39 (158012)
11-10-2004 12:58 PM
Reply to: Message 12 by contracycle
11-10-2004 6:49 AM


quote:
Is [tolerance to alcohol] genetic though? Because I wonder how much of that might arise from the integration of the mothers and childs bloodstreams, and the exchange of chemicals and hormones et al.
Yep, it is genetic. Europeans have more copies of alcohol dehydrogenases (ADH) than Asians do. Europeans are able to metabolize ethanol at a prodigious rate when compared to some asians. Some asians, for instance, after one drink of alcohol get a very red face and stumble around. Europeans just get thirsty after one beer, and a little tipsy at times.
Native Americans have a different problem. They drank no alcohol whatsoever before the arrival of Europeans. Many native americans metabolize alcohol through a different pathway than Europeans. This different pathway results in a highly addictive byproduct. I'll look up more info if you want.
Added in edit: DOH, Mam beat me to it. Should have read the entire thread before posting. I am wondering if the alcohol dehydrogenases and aldehyde dehydrogenases are the same. ADH reacts ethanol with NAD to produce acetaldehyde and NADH. I am wondering if ADH's reverse reaction is refered to as ALDH. Anyway, that should answer your questions.
This message has been edited by Loudmouth, 11-10-2004 01:01 PM

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pink sasquatch
Member (Idle past 6013 days)
Posts: 1567
Joined: 06-10-2004


Message 22 of 39 (158153)
11-10-2004 6:05 PM
Reply to: Message 21 by Loudmouth
11-10-2004 12:58 PM


addiction
Many native americans metabolize alcohol through a different pathway than Europeans. This different pathway results in a highly addictive byproduct.
On top of this, some Native Americans have a heightened addiction susceptibility genotype - meaning addiction to any chemical substance from nicotine to heroin. There is a high correlation amongst propensity to addiction to multiple substances. I believe this might be true for non-Native Americans as well, but the susceptibility is much more extreme in some Native Americans and has led to the identification of some general "addiction" QTLs separate of alcohol metabolism.
Unfortunately it isn't published yet - I saw it in a talk by KC Wilhelmsen.

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contracycle
Inactive Member


Message 23 of 39 (158278)
11-11-2004 4:52 AM


I find this fascinating, not least because alcohol-gathering in africa is established and low tech, so I had kinda assumed that it was a very early development. Again, several animals produce types of alcohol as well. But this would all suggest that serious accomodation of alcohol occurs after homsap is geographically separated to a significant degree.

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Loudmouth
Inactive Member


Message 24 of 39 (158407)
11-11-2004 1:37 PM
Reply to: Message 23 by contracycle
11-11-2004 4:52 AM


I find it interesting as well. It seems that fermenting produce served two purposes. By allowing "good" fermentation to occur the food is preserved and potable. If "bad" bacteria/yeast ferment food products then it is lost, but adding some S. cervisae is always a nice way to preserve everything from yak's milk to fruit juices to grain products. If sugars are in abundance, then the fermentation does not completely convert all sugar to ethanol which preserves the food as an energy source. Also, yeast lysis during fermentation releases vitamins such as the B complex.
Of course the second purpose is social. Getting a little tipsy with your friends was perhaps the first past time (which may have eventually led to the oldest profession if you get my drift). Drinking may have helped to bond social groups as it does now.
Proscriptions surrounding alcohol use in each culture became important also. There are two routes. First, being drunk on a regular basis could have been considered to be taboo. Second, those humans whose physiology could handle large amounts of alcohol were able to function better in a society that drank on a regular basis. So the evolution of human physiology and culture could have been influence by a combination of memetics and genetics.

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Loudmouth
Inactive Member


Message 25 of 39 (158408)
11-11-2004 1:39 PM
Reply to: Message 22 by pink sasquatch
11-10-2004 6:05 PM


Re: addiction
quote:
On top of this, some Native Americans have a heightened addiction susceptibility genotype - meaning addiction to any chemical substance from nicotine to heroin.
When I wrote my original post that you quoted I was trying to remember the alternate metabolic pathway. My memory is foggy, but I thought it included a pyruvate byproduct. Either that, or I totally dreamt it up. Have you heard of this alternate alcohol metabolic pathway, or am I delusional?

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pink sasquatch
Member (Idle past 6013 days)
Posts: 1567
Joined: 06-10-2004


Message 26 of 39 (158833)
11-12-2004 3:47 PM
Reply to: Message 25 by Loudmouth
11-11-2004 1:39 PM


Re: addiction
I'm not remembering an alternate pathway, but that doesn't mean you are delusional. I think you mentioned reduced aldehyde dehydrogenase activity as a possibility - if my toxicology memory serves me correctly this might increase liver or systemic toxicity, but I'm not sure how it would effect dependency/addiction.
At least one genetic study found linkage to an alcohol dehydrognase:
Am J Med Genet. 2004 Aug 15;129B(1):110-5.
Genomic screen for loci associated with alcohol dependence in Mission Indians.
Ehlers CL, Gilder DA, Wall TL, Phillips E, Feiler H, Wilhelmsen KC.
Department of Neuropharmacology, The Scripps Research Institute, University of California, San Diego, California 92037,
Alcohol dependence is a leading cause of morbidity and mortality in Native Americans, yet biological factors underlying the disorder in this ethnic group remain elusive. This study's aims were to map susceptibility loci for DSM-III-R alcohol dependence and two narrower alcohol-related phenotypes in Mission Indian families. Each participant gave a blood sample and completed an interview using the Semi-Structured Assessment for the Genetics of Alcoholism (SSAGA) that was used to make alcohol dependence diagnoses and the narrower phenotypes of withdrawal, and drinking severity. Genotypes were determined for a panel 791 microsatellite polymorphisms. Analyses of multipoint variance component LOD scores for the dichotomous DSM-III-R phenotype revealed no peak LOD scores that exceeded 2.0 at any chromosome location. Two chromosomes, 4 and 12, had peak LOD scores that exceeded 2 for the alcohol use severity phenotype and three chromosomes 6, 15, 16 were found to have peaks with LOD scores that exceeded 2 for the withdrawal phenotype. Evidence for linkage to chromosomes 4 and 15, and 16 have been reported previously for alcohol related phenotypes whereas no evidence has as yet been reported for chromosomes 6 and 12. Combined linkage and association analysis suggest that alcohol dehydrogenase 1B gene polymorphisms are partially responsible for the linkage result on chromosome 4 in this population. These results corroborate the importance of several chromosomal regions highlighted in prior segregation studies in alcoholism and further identify new regions of the genome that may be unique to either the restricted phenotypes evaluated or this population of Mission Indians.

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wormjitsu
Inactive Member


Message 27 of 39 (160367)
11-17-2004 5:06 AM
Reply to: Message 26 by pink sasquatch
11-12-2004 3:47 PM


I wonder, are there any instances wher humans genetically mutated because of intense physical exersion? ei:slavery

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coffee_addict
Member (Idle past 467 days)
Posts: 3645
From: Indianapolis, IN
Joined: 03-29-2004


Message 28 of 39 (160375)
11-17-2004 5:45 AM
Reply to: Message 27 by wormjitsu
11-17-2004 5:06 AM


What do you mean? Are you talking about mutation in first generation or mutation in second generation? First generation means Scott suddenly gains an extra chromosome from working 23 hours a day in an alien slave labor camp. Second generation is when Scott remains normal but for some darn reason Scott Junior gains an extra chromosome.
Anyhow, the answer is no to either case. I'm not talking about gaining an extra chromosome. I'm talking about mutation in general. Any kind of mutation that is observed is a result of randomness not physical exersion.
However, slavery might result in artificial selection that would result in certain characteristics appearing more frequently than normal. For example, if Scott happens to be big and strong, Scott's master would certainly send him off to mate with Sarah, April, Christine, and a whole bunch of other female slaves so Scott's master could have more slaves that are big and strong like Scott.

Hate world.
Revenge soon!

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wormjitsu
Inactive Member


Message 29 of 39 (160739)
11-17-2004 8:37 PM
Reply to: Message 28 by coffee_addict
11-17-2004 5:45 AM


Intresting, Lam. So other than random mutations, natural selection is the only other way you will see genetic changes in the overall slave class.

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coffee_addict
Member (Idle past 467 days)
Posts: 3645
From: Indianapolis, IN
Joined: 03-29-2004


Message 30 of 39 (160778)
11-17-2004 10:13 PM
Reply to: Message 29 by wormjitsu
11-17-2004 8:37 PM


wormjitsu writes:
So other than random mutations, natural selection is the only other way you will see genetic changes in the overall slave class.
Well... it's somewhat complicated. There are some environmental influence that would cause an increase in the likelyhood of mutation taking place. Take the Chornobyl incident, for example. There were a lot of children that were born without spines, arms, legs, and lots of other abnormalities. I don't know if you would call that mutation, DNA damage, or just interuptions during fetal developmental stages.

Hate world.
Revenge soon!

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Replies to this message:
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