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Old 07-14-2010, 09:09 PM   #61
Katherine Derbyshire
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Re: Study finds correlation between C.O.G. and Speed

Just because evolutionary pressure has moderated now doesn't mean that such has always been the case. If something like improved vitamin D absorption gives you, say, a 10% greater chance of survival, then light-skinned people will be 10% more prevalent in the next generation. It won't take long for light skin to completely dominate the population.

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Old 07-14-2010, 09:30 PM   #62
Steven Low
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Re: Study finds correlation between C.O.G. and Speed

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Originally Posted by Katherine Derbyshire View Post
Just because evolutionary pressure has moderated now doesn't mean that such has always been the case. If something like improved vitamin D absorption gives you, say, a 10% greater chance of survival, then light-skinned people will be 10% more prevalent in the next generation. It won't take long for light skin to completely dominate the population.

Katherine
That's improper application of population genetics....

Also, a favorable trait does not mean that it will be passed on; it's likely that it will be passed on barring unforeseen circumstances though. Depends on the amount of adaptability and advantaged conferred though.

Anyway, I don't feel like talking about this stuff so I'm gonna skip out now..
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Old 07-15-2010, 05:26 AM   #63
Jason Wallis
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Re: Study finds correlation between C.O.G. and Speed

It has been suggested that we, as a species, will become more lazy less intelligent in future generations as these traits no longer carry a penalty from mother nature. I have read almost nothing on the subject, but on the surface that theory does warrant some consideration.
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Steven,
So my quesion is, what observable trait is so detrimental in any human you see today that would suggest that those people would die off?
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Old 07-15-2010, 06:52 AM   #64
Steven Price
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Re: Study finds correlation between C.O.G. and Speed

Ashhion, What you are arguing is that natural selection and adaptation are not real phenomena. This simply is not the case—it has been demonstrated in the laboratory as well as the field in countless cases. In humans, one of the first examples is of malaria resistance in Africa and it’s effect on sickle cell anemia frequencies. This is an absolutely now classic case, and backed up by laboratory stories, as about as scientifically air tight as you will get:

http://en.wikipedia.org/wiki/Sickle-cell_disease wfs

And certainly explaining the ancestral distribution of skin color around the world by selecting for protection from exposure to sunlight/vitamin d production/uv protection is the best single theory that has been advanced for explaining skin color distribution (interesting exception being Inuit, but they get vitamin d from a unique diet) and is not questioned by scientists, to my knowledge. If you know of any counter arguments supported by peer reviewed results I’d love to see it.

http://en.wikipedia.org/wiki/Human_skin_color wfs

I suggest you go to the following link on a population genetics primer before posting a counter to the existence of selection.

http://en.wikipedia.org/wiki/Population_genetics wfs

Steven, Kathryn was essentially correct—what she was getting at was the “selection coefficient” which, when multiplied times the gene frequency of the character in question, and results in a shift in that characters gene frequency. That this is correct is as well established as F=ma in physics.

The issue is not whether or not a “parent” is going to die off; the issue is does a particular gene or combination of genes confer a reproductive advantage—even advantages of as little as 1% can have huge consequences over time. See above references.
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Old 07-15-2010, 09:21 AM   #65
Aushion Chatman
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Re: Study finds correlation between C.O.G. and Speed

"One-third of all indigenous inhabitants of Sub-Saharan Africa carry the gene, because in areas where malaria is common, there is a survival value in carrying only a single sickle-cell gene (sickle cell trait)."

-From the Wiki on Sickle cell and malaria (Interesting aside: I have one sickle cell gene and was told when I was 12 years old that if I had kids with a black woman our kids had a 25-30% chance of having sickle cell anemia...definitely affected me as I've never forgotten that conversation with the doctor...and I'm married to a white girl so proof's in the pudding).

So because Sickle Cell trait is a buffer to malaria those genes have been "selected" and passed on down the line because those who had one sickle cell trait genes were able to reproduce slightly more than those who didn't, got malaria and died.

That's fine and dandy..

But why then are there so many people without a sickle cell trait (~66% according to the wiki). I don't know how old Malaria is, but I'll bet it's pretty old. Shouldn't the trait be more prevelant? And if it is not, how can we even statistically say that Sickle Cell is being selected for because of Malaria if the numbers don't or can't show that due to genetic drift, maybe we're just making it more complicated than it really is adding the "selection" piece to it.

I have the trait, got it from my dad, but my neither of my sisters have it...If they have more kids than me....

So let's look at the numbers in the US...

"1 in 500" (blacks) has sickle cell in the US..." how long does it take to go from being an advantage to obviously barely a blip on the screen. Are the numbers so low because there are only ~1,000 reported cases of malaria in the U.S. annually. That would suggest "selection" is happening at a highly observable pace. Most black people in the U.S. today trace back to sub-saharan where malaria was prevelant, in just 400 years we've gone from 33% affected to 1 in 500? That suggests we should be able to track and observe the numbers in one or two generation's worth of data collection. I hope someone is collecting that.

This <- (article) seems to state that malaria is going nowhere and is in fact increasing. Which should mean a trailing increase in sickle cell carriers in high malaria affected populations. this to me should take a LONG time, but given the number between US Sickle Cell trait and Africa, maybe it shouldn't take that long...


"Without endemic malaria from Africa, the sickle cell mutation is purely disadvantageous and will tend to be selected out of the affected population"

These are the numbers that are most interesting to track...will sickle cell be stamped out if malaria is relatively under control. Unfortunately malaria is not under control. And these are exactly the numbers that are missing. If we cannot say that overtime an increase in Malaria is leading to more sickle cell carriers, then what really have we got? I would love to see stats on Malaria and Sickle Cell anemia...as they should go hand in hand and you can predict the genotype Sickle Cell trait numbers from the number of homozygotes (anemics) correct?

thanks for the articles...I know I don't understand all of it, as I've only perused through them...hopefully my questions answers aren't buried in the literature.
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Old 07-15-2010, 10:12 AM   #66
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Re: Study finds correlation between C.O.G. and Speed

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Originally Posted by Angelina Kelly View Post
Ok this discussion is interesting overall and we recently had a discussion in our statistics class about avoidance of using race as a factor in statistics. Although I think our ancestry can have a basis for some of our tendencies.

Although this below is the craziest thing I've ever heard and I've never heard any basis to suggest such a thing, where the hell does this idea come from:
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Originally Posted by Aushion Chatman
The second is from evolutionist theory that blacks evolved from strong/but less intelligent gorillas, Asians evolved from the orangutan (smarter than gorillas), and whites evolved from the most intelligent primate of all the chimpanzee
Sorry, I missed this...here's where it got it's most prevelant start:

"The great break in the organic chain between man and his nearest allies, which cannot be bridged over by any extinct or living species, has often been advanced as a grave objection to the belief that man is descended from some lower form; but this objection will not appear of much weight to those who, from general reasons, believe in the general principle of evolution. Breaks often occur in all parts of the series, some being wide, sharp and defined, others less so in various degrees; as between the orang and its nearest allies—between the Tarsius and the other Lemuridae between the elephant, and in a more striking manner between the Ornithorhynchus or Echidna, and all other mammals. But these breaks depend merely on the number of related forms which have become extinct. At some future period, not very distant as measured by centuries, the civilised races of man will almost certainly exterminate, and replace, the savage races throughout the world. At the same time the anthropomorphous apes, as Professor Schaaffhausen has remarked, will no doubt be exterminated. The break between man and his nearest allies will then be wider, for it will intervene between man in a more civilised state, as we may hope, even than the Caucasian, and some ape as low as a baboon, instead of as now between the negro or Australian and the gorilla.". -The Descent of Man, Charles Darwin
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Old 07-15-2010, 10:25 AM   #67
Aushion Chatman
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Re: Study finds correlation between C.O.G. and Speed

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I’m a population geneticist and evolutionist. As the name implies, population geneticists spend their time studying genetic differences between populations. All organisms that have been studied show genetic differences between populations for many, many characteristics. These types of studies have been going on for 100+ years. The literature is overwhelming. Many different words have been developed to describe these “genetically different populations.” If you are a plant population geneticist, and you can show some correlation of genetic structure with the environment, then you might chose to use the word “ecotype.” So a particular plant species may be divided up in to “ecotypes.” If you study mice populations you might use the word “race.” You would say that your mouse species was divided up in to various “races.” If these “races” were widespread and recognizable, and you were a taxonomist, you might divide your species into “subspecies.” “Subspecies” is a word used for both plants and animals. If you were a horticulturist, you might use the word “variety.” If you were a corn breeder you might use the word “line.” If you are studying paternal Y-Chromosome variation around the world in humans you might use the word “haplotype.” In the latter case you migh say "haplotype R1b1b2a1a1d1* is wide spread in populations of the North Atlantic." My point in this is that many words are used to describe “genetic variation.” If races exist in other organisms, then, as an evolutionist, it is reasonable to assume races exist in humans. To assert that “races” do not exist in humans simply does not square with genetic evidence or biology. Pygmies are genetically different from indigenous populations of Sweden. Most population geneticists would say they are different races. DNA evidence is showing fascinating patterns of genetic variation around the world; it is contributing greatly to our understanding of human origins and migrations. Modern medicine is now recognizing that there are “racial” differences in response to medicines. It would be a shame if medical practicioners were to become blind to patients’ racial differences—this may be good politics but bad medicne, bad biology, and bad science. To say that we all come from sub-Sahara Africa says nothing about the intervening 50,000 years of genetic changes due to genetic drift, natural selection, hybridization with other hominids, and migration. Sorting out how these all work to explain the present genetic differentiation found in Homo sapiens continues. Science is inexorable.
I missed this too, how genetically different do you have to be to be a "different" race. Why would skin color be the gene trait chosen. Is skin color such a driving force naturally that it is indicative of numerous observed traits? I think you may initially say Yes to that. But think about all the observed human phenotypes, it is quite possible to group people into many different population groups based on many traits other than skin color.

I understand that using skin color as the determinant for race is a good indicator of a community (Nationality!) But it doesn't by any means tell the whole genetic story...You conveniently chose two populations with two traits on opposite ends of the spectrum (your example of Swedes and pygmies, the two traits being tall/white, short/black), but there are many more genes that they may or may not have in common. Instead of looking at two traits on the outside, isn't it more scientific to actually observe the averages on gene traits and see just how divergent their DNA really is? Is it not conceivable that pygmies and swedes may be genetically closer than swedes and the maasai? There's a disparity there, what about swedes and pakistanis vs swedes and the pygmy...

Isn't it better science & medicine to determine which medicines are genetically acceptable then to just say, "well you got white skin, chances are this will help you." I think it's not a loss of science to stop thinking about race, I think it will actually help science not be so lazy at classification and development of things like medicine and abnormality prediction...
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Old 07-15-2010, 10:41 AM   #68
Jamie J. Skibicki
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Re: Study finds correlation between C.O.G. and Speed

"Isn't it better science & medicine to determine which medicines are genetically acceptable then to just say, "well you got white skin, chances are this will help you." I think it's not a loss of science to stop thinking about race, I think it will actually help science not be so lazy at classification and development of things like medicine and abnormality prediction... "

Color isn't the main determination. Example, east africans and west afircan have the same skin color, but have markedly different genetic predispositions. THe same holds true for gauls and anglo saxons.

You will find similarites amoungst group with the same skin color as there environments that favor drak skin pigmentation will have some similarities as the environments that favor light skin pigmenation will. The fact that you can guess where someone (or at least their ancestors come from) would suggest that changes have and are happening.

SO you can make broad determinations based on skin color, but you are much more accurate when you start to differentiate by region.

And the point about swedes an dpygmies was that genetic traits are not evenly distributed in populations. You don't find many asians with blue eyes and you don't find many scandavians who are short.

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Old 07-15-2010, 11:54 AM   #69
Steven Price
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Re: Study finds correlation between C.O.G. and Speed

Aushion,
The reason that sickle cell survives in those populations under attack from malaria is that it is the heterozygote that shows resistance to malaria. So the sickle cell genes will never be eliminated from the population. Given, as you say, that the frequency of sickle cell is 0.33, the gene frequency would be the square root of this, or 0.57. The expected number of heterozygotes WITHOUT selection would be 0.57 x 0.42 x 2 (Hardy-Weinberg assumption—see population genetics primer) = 0.48, and the number of homozygotes for the dominant allele would be 0.42 x .42 = 0.18. The point is that the heterozygotes will keep the frequency very high for both genes (alleles). And that is what the data shows. (assuming I didn’t’ mess the arithmetic).

Your quote from Darwin of course represents a “best guess” as of 1871. This theory is not held by ANYONE today; however just as an fyi, he also posited that Homo sapiens arose in Africa, which has since been validated, and was counter to the prevailing theory at the time, which was the site of origin was in Indonesia.

The fact of the matter is that data shows that skin color is statistically associated with many other genetic differences (1000's). See below as an example:

http://en.wikipedia.org/wiki/Human_genetic_variation

You will note that if you look at the chart on the right side that skin color would overlay pretty well this distribution. There are exceptions, but not many.

In fact self-reporting of “race” by patients is now seen as a major step forward for the treatment of hypertension, Tay Sachs, prostate cancer, and diabetes.

I fail to see why recognizing race is "lazy" science. It is rooted in 100 years of study. Humans are animals, with an evolutionary history. Human populations have had different histories. Race is just a lumping of populations--just a helpful vocabulary word that integrates over well established differences. Why throw out useful words?
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Old 07-15-2010, 12:13 PM   #70
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Re: Study finds correlation between C.O.G. and Speed

Jamie,

Paragraphs:

1) Agree

2) Disagree, why is dark skin a genetic advantage near the equator (in the tropics)...?

Are all animals darker in the tropics? No, in most cases animals from hotter regions are lighter not darker to reduce solar absorption as heat exhaustion and heat stress are MUCH quicker killers than skin cancers. It would seem to me having skin that absorbs more heat (darker), is much more immediately dangerous as a disadvantage to a species than protecting against slower killing uV rays. Overheating would actually have teh ability to deter animals from reproducing as it could kill earlier in life. A skin cancer, would take much longer, especially since natural instinct for all animals is to seek shade when overheated...Most skin cancer is associated with people who spend too much time in the rays despite instincts..."tanning"

In fact the "tan" that develops temporary darker skin is the first sign of DAMAGE, not adaptation.

So skin cancer itself could not be a vehicle for selection as it takes too long to develop and would not deter any from reaching reproductive age and having offspring.

3) Agree

4) Disagree, his point was to infer that Swedes and Pygmys are different races...not that traits are evenly distributed. Read his post again... He says modern medicine is discovering "racial" responses to medicine...to which my reply is simply, why on earth would a non-epidermal medicine not care one way or the other about skin color?

By definition race is a faulty term, and it is bordering on the ridiculous to think a medicine affects this person or that person different because their "race" is different. It would be because their genetics are different, no more no less. Skin color may or may not be a correlate. Like YOU said, there are genetic differences between East and West Africans...
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