Can recessive genes make a comeback or be preserved?

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K_Kelly
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11 Dec 2014, 5:36 pm

I don't know, but I'm really concerned about the blonde hair and blue eyes genes in humans, because some of the studies reported those genes are less than 2% rare in adults. I may be biased since I have a preference for blonde over brunette girls. Only a slight preference though. But brunettes aren't the ones becoming more and more hard to find. I wish it was more easier to find a girl who is good-looking in my regard. Are there any experts here on the idea? And sadly there is nothing we can do about it if we don't turn into a white supremacist state. Unfortunately, they seem to be the only ones who care about them dying. I don't want to be demonized for it, I'm even very sad that it's happening. I don't want to be too dramatic and exaggerated, but I feel like I'm almost living a nightmare. :(



livnah
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11 Dec 2014, 5:40 pm

I think you don't understand how genes work...

A gene isn't "lost". A phenotype can be reduced, but the recessive genome is not "lost". Likewise, even if the gene isn't present at all in a population it can suddenly re-enter the gene pool thanks to the miracles of naturally-occurring mutation.

If you're worried about blondes "going away", remember to apply deodorant daily. It's a bit like people worrying about Ebola - the director of the CDC said, "if you suspect Ebola the best way to ensure your survival is to wear your seatbelt on your way to the hospital."


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K_Kelly
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11 Dec 2014, 6:03 pm

Thanks for correcting me. I'm sorry about the horrible white supremacist references by the way. I know being a supremacist isn't good, but they still feel the argument that blondes are dying out.

They may not die out but they are still getting much harder to find. I'm still worried about that too. With what you mentioned about genes, are you saying that diminishing phenotypes can still theoretically make a comeback?



livnah
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11 Dec 2014, 7:32 pm

Yes. I encourage you to read-up on studies about fair features becoming prominent during ice-age periods and in geographical areas prone to extended winters such as Scandinavia.


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livnah
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12 Dec 2014, 9:54 am

Wikipedia wrote:
Natural lighter hair colors occur most often in Europe and less frequently in other areas. In Northern European populations, the occurrence of blond hair is very frequent. The hair color gene MC1R has at least seven variants in Europe giving the continent a wide range of hair and eye shades. Based on recent genetic research carried out at three Japanese universities, the date of the genetic mutation that resulted in blond hair in Europe has been isolated to about 11,000 years ago during the last ice age.

A typical explanation found in the scientific literature for the evolution of light hair is related to the requirement for vitamin D synthesis and northern Europe's seasonal deficiency of sunlight. Lighter skin is due to a low concentration in pigmentation, thus allowing more sunlight to trigger the production of vitamin D. In this way, high frequencies of light hair in northern latitudes are a result of the light skin adaptation to lower levels of sunlight, which reduces the prevalence of rickets caused by vitamin D deficiency. The darker pigmentation at higher latitudes in certain ethnic groups such as the Inuit is explained by a greater proportion of seafood in their diet. As seafood is high in vitamin D, vitamin D deficiency would not create a selective pressure for lighter pigmentation in that population.

An alternative hypothesis was presented by Canadian anthropologist Peter Frost, who claims blond hair evolved very quickly in a specific area at the end of the last ice age by means of sexual selection. According to Frost, the appearance of blond hair and blue eyes in some northern European women made them stand out from their rivals at a time of fierce competition for scarce males.

A theory propounded in The History and Geography of Human Genes (1994), says blond hair became predominant in Northern Europe beginning about 3,000 BC, in the area now known as Lithuania, among the recently arrived linguistically Proto-Indo-European settlers (according to the Kurgan hypothesis), and the trait spread quickly through sexual selection into Scandinavia. As above, the theory assumes that men found women with blond hair more attractive.

It is now hypothesized by researchers that blond hair evolved more than once. Published in May 2012 in Science, a study of people from the Solomon Islands in Melanesia found that an amino acid change in TYRP1 produced blonde hair.


Also:

"Blonde hair evolved more than once" from Nature.com -- http://www.nature.com/news/blonde-hair-evolved-more-than-once-1.10587


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K_Kelly
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12 Dec 2014, 4:03 pm

What does it mean by "evolved more than once".



Protogenoi
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13 Dec 2014, 11:37 pm

K_Kelly wrote:
What does it mean by "evolved more than once".


Let me give an example...
The American Curl is a trait cats can have. It first appeared in the 1980's and we know the first cat to have the trait as far as we know. It is actually a dominant trait (but still rare because the trait is so new.)

(I advise clicking the link to see the cool cats) LINK

So, if some mean horrible person destroyed all cats with the curl, then they would be gone.

However, even if they are killed off, they could appear again sometime in the future by random mutation again.


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naturalplastic
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15 Dec 2014, 10:02 pm

"Evolved more than once" means two groups of unrelated peoples had seperate mutations that cause the same trait.

Most humans cant digest milk as adults. But Europeans and Middle Eastern and Indian subcontinent people can as a rule digest milk as adults. Chinese and Black africans as a rule are lactose intolerant. This is because of genetic mutation in Eurasia a few thousand years ago allow grown ups continue their infant ability to digest milk. However there is also a small population of blacks in east africa (the Masaii in Kenya for example) who are also adult milk drinkers. They also have a special gene that allows that. But that gene is a different -unrelated to the gene in Caucasian Eurasian milk drinking races of the north. By coincidence the Masaii in Kenya had their own milk digesting mutation. So milk digesting 'evolved twice' in the human race.

The fact that a trait is recessive doesnt mean it disappears. It just means that it gets thinly spread out in the population. A hundred years ago blondes were confined to northern europe. A thousand years from now the blonde gene will be dispersed around the globe. The actual number of people who get a diploid supply "blonde" genes will be about the same as always they just will be thinly dispersed among the vast number of dark haired people. Instead of one percent of the population being blond- but having that one percent be clumped together as half of the population of scandanavia (with virtually no one in China or subsaharan africa being blonde)- one percent of the global population will still be blonde. But that one percent will be: one percent of the population of China, and one percent of Africa, and one percent of Scandanavia itsself, and one percent of of everywhere else. Kinda like cigarette smoke dispersing through your house.

What idiot concocted the theory that blondes in the ice age were "selected for" because they were "more sexually attractive"?

Blondeness was selected for because being blonde enabled your body to produce vitamin D (because any hair and skin pigment blocks the sun which powers vitamin D production) so you didnt die of starvation or of ricketts as a child in the least sunny continent on earth (Europe) during the stone age. Sexual attractiveness likely had nothing to do with it. It was not until madison avenue and clairol in the 20th centurey that folks were persuaded that "blondes had more fun". Ice Age folks probably thought blondes were hideous freaks, but more of them survived childhood to become sexually mature adults with each generation in that part of the world. So gradually they became the only game in town- so guys and girls alike were forced to pair off with members of the opposite sex who were blonde. Yuck! So gradually blondness became more common.But just in that one region of the world.

Actually it's possible that the proportion of blondes world wide is declining-but because the countries that have all of the blondes (only small areas of the northern part of the developed world) also happened to be the regions with declining birth rates. But thats another factor. Thats not because the gene is recessive.



michael517
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16 Dec 2014, 9:47 am

There is a way you can help to not have those genes leave the human population :wink:

I've done my share of passing on blue eyes and blonde hair traits.

Just a word of warning though, as a (male) co-worker pointed out to me once, "The ring is the cheapest thing." Which is to say, if you think buying that engagement ring was expensive, wait until you have to buy a bigger house, a minivan, strollers, diapers, braces, glasses, fix broken smart phones, a dress for prom, or college.