Should I be wearing sunblock? I spend the vast majority of my time inside, so I would like to start getting into cycling. I rode up to the beach a couple days ago and got some slight sunburn. I personally don't mind sunburn all too much, but the news has successfully instilled a fear of skin cancer into me. 

My initial reaction to articles like: http://shine.yahoo.com/healthy-living/the-new-rules-of-sun-safety-2477938.html that make claims such as:


  It's not smart to go out-of-doors unprotected. 


..was that the writers were absolutely nuts. We've spent our entire evolutionary history under the sun - to think that short excursions outdoors would be dangerous seems ludicrous. But then, people are living much longer than they ever did before and, if there are dangerous aspects of sun exposure, the increase in greenhouse gases might be adding to them.

So, does anyone know the reality behind all of this? Should I wear sunblock, or is skin cancer only a risk for people outside all day everyday?
We've spent our entire evolutionary history under the sun, but also aging quickly and dying at young ages. The evolutionary history argument just isn't very compelling.

The current consensus is that sunscreen helps prevent skin cancer, and skin cancer is indeed common. On the other hand, I have seen references to theories suggesting that sunscreen might increase a certain type of cancer or decrease vitamin D production, but these do not seem to be widely accepted. An in-depth discussion of this is probably more appropriate for Skeptics.SE than Bicycles.SE.

In the meantime, just use sunscreen.

EDIT: As heltonbiker pointed out, burning and cancer susceptibility depend on your skin, and most people develop some protection from tanning. I personally wear sunblock during mid-day rides (between about 11:00 and 3:00), when the sun is directly overhead, but I'll leave it off for evening and early morning rides.

If you're burning instead of tanning (even if you don't mind the burns), you're probably getting too much exposure and should use sunscreen more often.