CrossFit Discussion Board  

Go Back   CrossFit Discussion Board > CrossFit Forum > Fitness
CrossFit Home Forum Site Rules CrossFit FAQ Search Today's Posts Mark Forums Read

Fitness Theory and Practice. CrossFit's rationale & foundations. Who is fit? What is fitness?

Reply
 
Thread Tools
Old 07-20-2010, 11:06 AM   #111
Aushion Chatman
Affiliate Aushion Chatman is offline
 
Aushion Chatman's Avatar
 
Profile:
Join Date: Dec 2004
Location: San Diego  CA
Posts: 3,342
Re: Study finds correlation between C.O.G. and Speed

Quote:
Originally Posted by Katherine Derbyshire View Post
UV light, for instance, is a pretty powerful mutagen. It's a bad example for purposes of this debate, because the first humans probably produced melanin already. But you can imagine a completely melanin-free population: some people would get skin cancer and die, but some might get a beneficial mutation allowing them to produce a UV-blocking pigment. Offspring with the mutation would have a survival advantage, and away we go.

You also get mutations due to copying errors in the cell division process. And you get non-mutational changes in a population as it is exposed to other groups. But yes, mutation rates are one of the biggest sources of contention in the various debates about evolution.

Katherine

This is a tough example as the expression of melanin doesn't mean melanin-free...but I see what you are saying...but to me this would mean a population would die off rather quickly which is why I kept saying it would need to be a life or death type of situation as like you said, not just rates of mutation but rates of mutation dominance would seem to take a long time....

Again I believe the code for lighter skin humans was always there in our middle of the road complexion ancestors I do NOT believe the first ancestors were black...
__________________
My Youtube Channel
CFSD Yelp
  Reply With Quote
Old 07-20-2010, 11:37 AM   #112
Allen Tluczek
Member Allen Tluczek is offline
 
Allen Tluczek's Avatar
 
Profile:
Join Date: Oct 2009
Location: Grand Rapids  MI
Posts: 629
Re: Study finds correlation between C.O.G. and Speed

Aushion: I'll refer you to "Climbing Mount Improbable" by Richard Dawkins. That or "The Blind Watchmaker." (I read them both back to back a few months ago, and the many similarities between the two have jumbled them in my mind) I think Improbable was the better of the two in explaining the process of variation and speciation, but as I said the two books are very similar, and I honestly can't really remember which book had what when I think back to illustrations of the concept.

Concerning the first bolded question, I really am unsure of what the issue is. No two people have identical DNA. The expression of different DNA is what results in different people. Therefore, there is genetic variation among any population. So say on one island the trees only grow tall, and the fruit only falls after it has rotted and become unedible. Given the natural range of height among a population of an animal living there, the taller individuals would be able to reach more fruit and thus supply more offspring. Now the island splits in half, and half drifts to more extreme weather where the trees cannot grow as tall. The animals living there, with their genetic variation, wouldn't need to waste the energy required to grow tall, and the shorter individuals would be able to spend more energy producing offspring instead of growing taller. The DNA dosen't have to change, just the proportion of the expression of the heritable in a population. That is natural selection in a nutshell.
__________________
Crossfit is Algebraic!
My Withfit Log
  Reply With Quote
Old 07-20-2010, 11:56 AM   #113
Katherine Derbyshire
Member Katherine Derbyshire is offline
 
Profile:
Join Date: Jan 2009
Location: Seattle  WA
Posts: 7,596
Re: Study finds correlation between C.O.G. and Speed

Quote:
Originally Posted by Aushion Chatman View Post
I should clarify and ask:

How does selection of traits lead to a change in traits...Meaning the capacity for light and dark skin has always resided in the race's (I mean human race...heh) DNA. There was no change, just certain variations being predominant in certain environments...
Let's look at lactose tolerance. All human infants (and all mammalian infants) can digest lactose. But at a certain age, the ability to do so switches off. In most environments, though, the ability to digest lactose doesn't matter, and there's no evolutionary pressure for or against adult lactose digestion. So random variation gives you people who can continue to digest lactose until age 10, or into adulthood, and they survive just as well as the people who can't digest it past age 2. The variation is, as you said, already present in the genome. (On the other hand, any infants who can't digest lactose at all will probably die before reaching adulthood. So *that* part of the distribution will get wiped out pretty quickly.)

Then the tribe moves to northern Europe and domesticates cows. Suddenly they have a ready supply of milk, and people who can digest it have an additional food source that people who don't can't tap. Big competitive advantage. The people who can digest milk have more kids, and their kids are more likely to grow up. The evolutionary environment now favors people who can digest milk. And so the prevalence of lactose tolerance starts to shift until almost everyone can drink milk.

But even if the advantage of lactose tolerance goes away -- as it arguably has in economically rich Northern Europe -- the change to the population is permanent. Almost everyone is lactose tolerant, so most kids will inherit the lactose tolerant gene, as will their kids. The temporary "selection of traits" has led to a permanent "change of traits."

Katherine

Last edited by Katherine Derbyshire : 07-20-2010 at 11:58 AM.
  Reply With Quote
Old 07-20-2010, 12:50 PM   #114
Katherine Derbyshire
Member Katherine Derbyshire is offline
 
Profile:
Join Date: Jan 2009
Location: Seattle  WA
Posts: 7,596
Re: Study finds correlation between C.O.G. and Speed

Quote:
Concur, although if the invaders and the people invaded both had a common ancestor 1,000 years prior, how much of a cross-breed is it? Do you believe 1,000 years would be long enough to produce so many mutations common to the whole population observed at the time of invasion that the two populations have diverged to a large extent, where "cross-breed" is the correct term? Maybe 1,000 isn't long enough, how about 10,000 or even 100,000 years...Why?...To me that is as anecdotal as I was accused of being earlier. It sounds like a nice story, but I hope we can agree that it is not scientific to just assume that because 100,000 years passed in a different environment we know that a whole slew of DNA has CHANGED..not just that certain variation are more expressed, but CHANGED. This leaves you with ONLY mutation being a source of TRUE variation..meaning differences...not just trait prevelance (variation)
Let's say the base population originates in Africa 100,000 years ago. It splits into two groups, A and B. A stays put, B moves to Northern Europe as soon as the glaciers recede.

The environments in Africa and Northern Europe are completely different. Africa favors dark-skinned people, so all the light-skinned people die off. Group A becomes completely dark-skinned. Northern Europe favors light-skinned people, so all the dark-skinned people die off, and population B becomes completely light-skinned. The same thing happens with a bunch of other traits. 60,000 years or so later, in 1600, the descendants of population A and population B have measurably different DNA.

Quote:
Reproductive advantage then seems to imply less variation, not more when you put it like this...But I agree with this...Though now I think reconciling how less variation can lead to more might be a problem... Actually if all of the variation was already present in the genetic code I think it reconciles nicely.
Population B builds ships, invades Africa, kidnaps members of population A. Reproduction between members of the two groups leads to children (C) who have characteristics of both A and B. Populations A and B both became less diverse under the pressures of their environments, but merging the two groups pops the genetic diversity back up.

Quote:
I can't help but comment on the catch-all "or may not"... what if you put a population of people underground for 100 years and their grandkids come out with eyes sensitive to bright light, I think now we have to agree this is not evolution (micro or macro obviously) it was adaptation and it was a product of the environment, and when you bring them out in another 100 years their off-spring's eyes will be just like everyone else's that lives above ground. There was no loss in genetic traits (selection). There was no change in DNA (mutation). They are not now a sub-species (micro...eventually macro evolution).

This is a very different mechanism than random mutation as mutation would have necessarily taken a VERY long time to be observed as the dominant trait. This is adaptation at its quickest and finest and with tools in the genetic code that were already present. This is what I originally thought micro-evolution was, but it is not apparantely, leading me to believe that I do not believe in micro-evolution either. This doesn't work for skin color...or does it?
Was there evolutionary pressure that favored light sensitivity/insensitivity? (They fled underground in the first place because a hole in the ozone layer bumped up UV levels, causing cataracts and blindness in the people who stayed. A particularly yummy cave-dwelling fish can only be caught in near darkness, favoring people who can see in low light. That sort of thing.) If so, then you might have evolution toward a more light sensitive population underground. If not, then you're just seeing a short term response -- like turning the lights on suddenly -- not a genetic change.

Quote:
No debate really on many of the points above, I think the biggest problem is that it seems for micro-evolution you need to start with little to no variation..then have a mutation that is beneficial.
Not true. You start with whatever variation is present in the genome, from whatever source, then add selective pressure that favors a particular trait. Mutations and binary choices are easier to talk about, but the actual human genome is WAY more complex.

Quote:
3) Again selection seems to infer less variation...so we randomly get mutations...that have to overcome the above numbers game...

But then once we get enough variation selection starts to wittle it down, I'm not sure how we ever get to a new species with these antagonistic mechanisms?
Selection does start to whittle variation down, especially in extreme environments. This is known as a population bottleneck. Think of something like the Black Death, which killed everyone or almost everyone in some towns in Europe. Population bottlenecks are part of the reason why the human population is as genetically uniform as it is.

But, if there is a surviving population of the species elsewhere, it can bump the overall variation back up. Breeding programs to keep the surviving population as diverse as possible are one of the key elements in efforts to save endangered species. (And lack of genetic diversity is one reason why some of those efforts are likely to fail.)

For speciation, consider what happens if two groups within a population (call them D and E) face selective pressures that force incompatible adaptations. Say environment D favors animals who can climb and swing from branches, while environment E favors animals who can stand upright. Even if the populations re-merge, an animal is likely to be compatible with either the D niche or the E niche, not both, and will therefore mate with animals who belong to that group. Instead of re-merging to form group F, D and E will continue to be separate populations, and will get further and further apart over time.

Katherine
  Reply With Quote
Old 07-20-2010, 01:05 PM   #115
Steven Price
Member Steven Price is offline
 
Profile:
Join Date: Jan 2008
Location: Stillwater  OK
Posts: 54
Re: Study finds correlation between C.O.G. and Speed

Ashion, I just can't stay out of the discussion. YOU MUST go read a web site or book on INTRODUCTORY POPULATION GENETICS. There you will find equations/graphs/simulations taking into account different mutation rates, selection rates and projecting how many generations are required to change a gene frequency by a certain amount. All of your questions will be answered if you just go READ! This math was all done 75 years ago. If you like math, then you can really get into this.

I also have to address your implication of all genes that are present today were present long ago, of which you gave your skin color example. This is NOT THE CASE. Your observation that the furthest you get from Africa the less genetically diverse the population is IS NOT BECAUSE SUCCESSIVE POPULATIONS ARE SUBSETS OF ONES BEFORE. It IS TRUE that African Homo sapiens is genetically the most diverse of all regions in the world. It IS NOT TRUE that ABORIGINAL AUSTRALIANS are a subset of this. What is found is that if Africa has genes at a locus of A,B,C, and Aboriginies have C,D. So in this simple example Africa has more diversity but Aboriginies have some different genes. These genes arose most probably by mutation. We are also finding this with comparisons of Homo sapiens and Homo neanderthalensis---they interbred, but Neanderthals had genes we do not have, though there was considerable overlap.
  Reply With Quote
Old 07-20-2010, 02:11 PM   #116
Aushion Chatman
Affiliate Aushion Chatman is offline
 
Aushion Chatman's Avatar
 
Profile:
Join Date: Dec 2004
Location: San Diego  CA
Posts: 3,342
Re: Study finds correlation between C.O.G. and Speed

Quote:
Originally Posted by Steven Price View Post
Ashion, I just can't stay out of the discussion. YOU MUST go read a web site or book on INTRODUCTORY POPULATION GENETICS. There you will find equations/graphs/simulations taking into account different mutation rates, selection rates and projecting how many generations are required to change a gene frequency by a certain amount. All of your questions will be answered if you just go READ! This math was all done 75 years ago. If you like math, then you can really get into this.

I also have to address your implication of all genes that are present today were present long ago, of which you gave your skin color example. This is NOT THE CASE. Your observation that the furthest you get from Africa the less genetically diverse the population is IS NOT BECAUSE SUCCESSIVE POPULATIONS ARE SUBSETS OF ONES BEFORE. It IS TRUE that African Homo sapiens is genetically the most diverse of all regions in the world. It IS NOT TRUE that ABORIGINAL AUSTRALIANS are a subset of this. What is found is that if Africa has genes at a locus of A,B,C, and Aboriginies have C,D. So in this simple example Africa has more diversity but Aboriginies have some different genes. These genes arose most probably by mutation. We are also finding this with comparisons of Homo sapiens and Homo neanderthalensis---they interbred, but Neanderthals had genes we do not have, though there was considerable overlap.
Are you absolutely sure that gene D wasn't deselected over time in Africa? Again this sounds as anecdotal as my rebuttals have been.
__________________
My Youtube Channel
CFSD Yelp
  Reply With Quote
Old 07-20-2010, 02:14 PM   #117
Aushion Chatman
Affiliate Aushion Chatman is offline
 
Aushion Chatman's Avatar
 
Profile:
Join Date: Dec 2004
Location: San Diego  CA
Posts: 3,342
Re: Study finds correlation between C.O.G. and Speed

Anyway i could respond all day with my current knowledge level with stuff I don't understand or conclusions I draw that don't seem to fit with some of you here...let me go read as Stephen suggested and I'll PM..

I agree Stephen it is hard to stay out of this conversation so please no more responses

We'll reconvene in 6 months...I have it on my outlook calendar!
__________________
My Youtube Channel
CFSD Yelp
  Reply With Quote
Old 07-20-2010, 02:35 PM   #118
Steven Price
Member Steven Price is offline
 
Profile:
Join Date: Jan 2008
Location: Stillwater  OK
Posts: 54
Re: Study finds correlation between C.O.G. and Speed

Ashion, you can't have it both ways--you either believe that gene frequencies change or you do not. Of course gene "D" could have existed in an ancestral population, and then was lost. Since Homo has been in Africa for 2.3-2.4 million years, theoretically most mutations seen today may have arisen at one time or another. That is not the point. The point is that Homo sapiens in Africa is genetically different than Homo sapiens in Australia, and that Australian populations are not simply a subset of Africa's. That mutation is a real force has been shown 1000's of times in as many organisms. Mutations can be artificially induced or they can arise naturally. They are well understood at both the level of DNA and at the chromosomal level (ex. inversions, translocations). Gene mutations are the source of new variations that natural selection works on, and would not, by itself, be a force resulting in significant gene change. Coupled with genetic drift or selection, they can go to fixation very rapidly.

http://www.genetics.org/cgi/content/full/164/2/797

Additionally, mutation rates have been found to be pretty constant, like radioactive decay. Consequently the idea of "molecular clocks" (go ahead an Google this, too), has been very well established--and have been used to predict how long ago various species have diverged. Fossil rates and molecular clock rates have been found to be pretty concordant in studies of Homo.

Its just a beautiful world.
  Reply With Quote
Old 07-20-2010, 02:46 PM   #119
Steven Price
Member Steven Price is offline
 
Profile:
Join Date: Jan 2008
Location: Stillwater  OK
Posts: 54
Re: Study finds correlation between C.O.G. and Speed

Ha! OK, you gave me a good laugh for the end of the day. We need an icon selection that would portray a matdor and a bull....if you tell me you have been just waving a red flag I'm going to scratch my eyes out. :stir:
  Reply With Quote
Old 07-20-2010, 07:59 PM   #120
Aushion Chatman
Affiliate Aushion Chatman is offline
 
Aushion Chatman's Avatar
 
Profile:
Join Date: Dec 2004
Location: San Diego  CA
Posts: 3,342
Re: Study finds correlation between C.O.G. and Speed

Quote:
Originally Posted by Steven Price View Post
Ha! OK, you gave me a good laugh for the end of the day. We need an icon selection that would portray a matdor and a bull....if you tell me you have been just waving a red flag I'm going to scratch my eyes out. :stir:
HA! I can't believe that emoticon doesn't exist...

edit: closest I could find...
Attached Thumbnails
Click image for larger version

Name:	torro_thumb_s.jpg
Views:	114
Size:	3.1 KB
ID:	6634  
__________________
My Youtube Channel
CFSD Yelp

Last edited by Aushion Chatman : 07-20-2010 at 08:06 PM.
  Reply With Quote
Reply


Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is Off
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Study finds danger in PROCESSED meat Todd Crawford Nutrition 4 05-19-2010 02:39 PM
Of causation, correlation and calories Kurt Armbruster Nutrition 1 08-07-2009 08:49 AM
Study finds HFCS contains mercury Alex Sohn Nutrition 2 01-28-2009 11:39 AM
Paleo study finds positive effects on insulin sensitivity and blood pressure. Tim Donahey Nutrition 0 02-06-2008 05:40 PM
Low-Fat Diet Does Not Cut Health Risks, Study Finds David Wood Nutrition 4 02-10-2006 07:46 AM


All times are GMT -7. The time now is 01:14 PM.


Powered by vBulletin® Version 3.6.8
Copyright ©2000 - 2020, Jelsoft Enterprises Ltd.
CrossFit is a registered trademark of CrossFit Inc.