BluEyes said:
Humans have been living naked in the shrubs for millions of years, spending many hours a day in direct sunlight. Two thousand years of loincloths and hoodies isn't going to reverse our natural protection from UVA rays. The simple fact is most kids(and adults now too) now spend hours on playstation, world of warcraft, and watching the O.C. instead of out in the sun playing footie with their mates.
I think we are not on the same page. I am not talking about hanging out on the beach for 10 hours a day, burning and reburning your skin, I'm talking about simply exposing your skin to the sun. Which technically IS damage to your skin, but as long as you don't overdo it and listen to your body, it can only be HEALTHY.
Let's not start a flame war here. I am expressing my opinion, you are expressing yours.
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It seems in your argument that you're saying that every time you go out in the sun you should wear sunblock or something...
Tan
You call that unhealthy?
Master Bates is Very Correct...
Blue Eyes, I believe your passionate response has very little factual information to defend your position.
Average longevity started to increase around the year 1900 ~ mid 40s with advances in sanitation, antimicrobials, and medicine. Prior to 1900 most people lived from 20-35, with most individuals died from infectous disease. So how can you say that what is programed in our genome over the past 100,000 years confers us protection from long term exposure to UVA rays. It is not. We were dead before the skin cancer got us, in the Western World Avg. life expectancy is in the mid-70s. 100 years is snapshot in evolutionary terms. This is especially the case of individuals who are of Northern Latitude descent with fair skin and eyes, darker pigment skin that arose as adaption to equatoral region confirms a 'natural spf of ~15.'
Stated by Wiki in simple terms:
"Dark skin protects against those skin cancers that are caused by mutations in skin cells induced by ultraviolet light. Light-skinned persons have about a tenfold greater risk of dying from skin cancer under equal sun conditions. Furthermore, dark skin prevents UV-A radiation from destroying the essential B vitamin folate. Folate is needed for the synthesis of DNA in dividing cells and too low levels of folate in pregnant women are associated with birth defects.
While dark skin protects vitamin B, it can lead to a vitamin D deficiency. The advantage of light skin is that it does not block sunlight as effectively, leading to increased production of vitamin D3, necessary for calcium absorption and bone growth.
The evolution of the different skin tones is thought to have occurred as follows:the haired ancestors of humans, like modern great apes, had light skin under their hair. Once the hair was lost, they evolved dark skin, needed to prevent low folate levels since they lived in sun-rich Africa. (The skin cancer connection is probably of secondary importance, since skin cancer usually kills only after the reproductive age and therefore does not exert much evolutionary pressure.) When humans migrated to less sun-intensive regions in the north, low vitamin D3 levels became a problem and light skin color re-emerged."
(source
http://en.wikipedia.org/wiki/Human_skin_color)
What is interesting the current social value of the 'TAN' suggests someone who is affluent and has the ability to fly to tropic locations. This is in contrast that at the turn of the century, those who were very Dark were field workers and other of lower social status. The concept of that the tan is healthy is social convention that arose in the Jet set age (say 1950's).
Clarification: most sun damage DOES NOT OCCUR a with single 10 hours exposure at the beach, but much more significant is the cumulative exposure we receive just doing daily activities...those 1-10 minute mini-exposures add up over days, weeks, months, years. If you commute by car side window auto glass does not protect against UVA rays. Think about long 1-3 hour commute many individuals do daily...so the UVA exposure is about 1-4 hours per day.
We (Master Bates and myself) were just suggesting that people use daily sun protection as part of their normal routine to retard aging and protect against skin cancers. Nothing more.
When I'm 50 I rather look 10 years younger than my chronological age, but that is just my opinion.
RD
