Humans have been exposed to sunlight for 10's of thousands of years.

Of course humans have come to depend on the Vitamin D synthesis with the Skin. With some 20 minutes per day exposure recommended on the face and arms as enough to fulfil this need.
We also know the Vitamin D is needed for cancer supression, bone-teeth-skin & hair growth, immune integrity, eye health, etc. All very important to human survival and hence Prana-positive.

So what's this thing about direct Solar radiation and Prana or life force depletion?

I dont know about you but I grew up in southern australia with long hot summers ans wet cold winters  and rarely suffered skin burns. HOWEVER the POWER of the SUN, on one's skin,  in these climes today IS VERY POWERFUL, HARSH; Some would say even opressive.
Also the incidence of Skin cancers in Australia of recent times is of epidemic proportions. Health Authorities exhort us to slip-slop-slap(Protect oneself with a hat & sunscreen) and in  general part we must agree. Further some would argue that the things such as Artificial lighting are the real blame for melanoma increase. In part we agree with this comment HOWEVER with changes so rampant in our atmospheric environment & 'holes-in-ozone-layers' we must now admit that sunshine 'these-days' aint-what-it-used-to-be.

One instance comes-to-mind lately of a young 18 yo woman who presented with a stubborn sexually transmitted illness. After our diagnostic session I commented that for one so young I had NEVER seen a life force so low (Even though her countenance was normal)… Around a minus 4 Prana points. I said that this is the area of life force where chronic disease begins to manifest. Further I pointed out that the ONLY THING I could find that  might explain her low level was a 'Natural radiation' buildup (Remember, the more you are exposed to radiation of ANY sort, the more the supression of your immune system, hence supression of Prana).
She just could not recount a reason as to why this would be the case until her mother commented that she had been badly sunburnt some 5 or 6 times in her early teens… Her cases of 'Sun burn' were not hospitalisation-stuff BUT enough to cause multiple blisters to occur on many areas of her body, each and every time of her exposure and each time needed up to 10 days to fully heal.

These days she definitely maintains just minor exposure to the sun. 

So, by all-means get your 20 minutes of sunshine per day but do think twice about too much more.