Human Anatomy, Physiology, and Medicine. Anything human!
Hey SHF, you're so right. The sun is only a catalyst in releasing Vitamin-D that is already in the body from food stuff. If i remember correctly (not attached) The stuff the turns into Vitamin-D just requires a certain amount of radiation to go through synthesis in the body.
Traveling to colder regions requires more warmth and shelter therefore limited amount of sun-time and less intense shore daylight. The body must adapt to keep the processes effective and keep you alive. I'm guessing as well fairer skin reflects light better therefore keep heat in.
I think the skin color difference is largely solved issue (UV, D-vitamin, melanin etc). There are respectable new studies including those of Nina Jablonski. There is rather good correlation between UV (UVA,UVB and UVC) high radiation and dark skin color.
However hair and facial differences are interesting issues too. Haven't red much about these issues but there must also be climate (dry, humid...), environment (forest, mountain, desert, hunting, fishing obtions etc) playing certain kind of role.
Diversity among Africans is actually much larger than among Asians, Europeans and Native Americans because those who left Africa were most of the time with relatively small groups and very isolated compared to those who stayed in Africa.
rswils:Not about beauty? Attractive mates exist in all cultures. Question was, what survival use necessitated large, broad noses, thick lips for only some tribes of Africa, Melasia, Alaskan Eskimos, Siberian Mongol, some Australian aborigines? All scattered across one half of the world. What common factors forged the similar change. Maybe jungle/desert/frozen habits are quite similar and food/water sources, oxygen requirements or enhanced scent tracking forced the mutation.
The title of this topic is just down right, sad. Amazing the title could not have read "why do some ethnicities have larger noses and lips, then others?" News Flash, every ethnicity has a share of large noses and lips it simply depends on the genes that run within that family line. Wow, education 1:1!
I don't know the answer to this specific question, but we do know some things about how genes are linked on DNA. Sometimes a trait that is helpful for survival is very closely associated with another trait on the DNA strand. So when natural selection keeps trait A in the gene pool as advantageous, trait B is also preserved. Trait B may confer no advantage, but it gets "carried along." I seem to remember reading something about this and that thick, lustrous hair in Asian women was somehow linked to smaller breasts. (I did not look that up. May be remembering wrong.)
I did a short experiment with some Afro Caribbean friends, the first test was for 3 participants to pinch their noses slightly to create slightly narrow nostrils, the other 3 participants were the control and did not have to do anything. The IV was pinching nostrils, the DV was the type of sound that was produced by both conditions. Both conditions were given a 50 word paragraph to read out aloud and the voices were recorded. The second test was a semi structured interview in which 2 participants, had to pinch their noses for 2 minutes and were interviewed to discuss the way they felt after. (FYI I did not have any experimental devices to gauge sound or measure air intake) The results for the first test, the experimental condition was voices changed dramatically and sounded more nauseated (sounded like when one has a blocked nose or has a cold) while the control did not change. For the second test, during the semi structured interview, participants confirmed that their nasal airway was restricted and breathing from the nose was harder and rather uncomfortable, that they were forced to breath through their mouth. From this short experiment we can deduce that narrowing nostrils means restricted airway passage thus limited breathing and limited O2 intake for black people. I think a more in depth and better equipped study is needed to show on how much air is been taken in an out by people with different nostril sizes and if there any differences and is this has any effect on physiology.
Found this at ScienceLet:
Disclaimer to begin with. There is nothing racist about this post or the topic. Of course not all Africans have large lips and not all Americans have small lips and of course large and small are relative.
The question that is being addressed is, how come most Africans have larger lips and a wider nose compared to, lets say Americans.
In general, this pattern can be observed across the planet with the size of lips and nose decreasing as we move away from the equator towards the poles. So what could the reason be?
(Average) Lips and Nose across different races
Given the pattern, it is an easy guess that the size of lips and nose has got something to do with the climatic conditions and that humans have evolved to fit into their world. The reasoning goes as follows.
Lips: For someone living in hot climatic conditions, cooling down the body is critical for their survival. Our body has many cooling mechanisms and one of them is simply disseminating heat when it comes in contact with colder air (simple thermodynamics). This however requires larger surface area so that more heat can be disseminated.
Given that a significant portion of breathing also happens through the mouth (especially when exposed to heat), lips are pretty much like the gateway for colder air being inhaled and exhaled. So, the larger the lips, the more heat that can be disseminated. Thus, people living in hotter climatic conditions gradually evolved to have bigger lips.
The opposite is true for people in colder climates. They get a survival advantage if they are able to retain as much heat as possible and so they gradually evolved to have smaller lips thus limiting the amount of heat that can escape when cold air brushes past their lips while inhaling and exhaling.
Nose: Its pretty much for the same reason as with the lips. Nose is the most important part when it comes to contact with colder air and having a bigger surface area helps with cooling.
There is one other advantage with a wider nose though. Physical activity in a hotter climate is more demanding than when it is cool (because the body needs to spend some energy just for the cooling processes) and thus the body requires more oxygen. Having a wider nose and nostrils facilitates breathing in more air thereby supplying the body with more oxygen and thus giving a survival advantage in the evolutionary race.
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