I saw headlines for this several times on google, but for some reason was not motivated to read the article. Health headlines go back and forth so frequently, that its only in today's obsessive culture that they could even be considered "news." Still, on reading the ABC version of the story,[1] I decided it is of interest.
The key fact to remember here, is that whether you believe in design or evolution, the fact remains that man, throughout history until the modern time, has spent the majority of each day outside without sunscreen. Both the primitive cultures of the American Indians, Africans and some of the Asian cultures and islands, and the historical cultures of Europe, the rest of Asia, and indeed, the rest of the world, had either a nomadic life, a hunting/herding/farming life, or both. Either would entail spending massive amounts of time outside. While the African and Indian populations, and to varied extents the Asian populations, have the higher pigmentation levels to help cope with sun exposure, the European would be outdoors no less. The so-called "farmer's tan" would have been the fate of many if not most European men (I am not addressing other localities here from a lack of information beyond the stereotypical movies).
From a design perspective, it then makes sense that the benefits of sun exposure would outweigh the risks. While the fall introduced death so completely that creation itself is subject to "futility" and corruption,[2] yet we know that it was created good, and that God does not suffer evil but causes a greater good to come from it.[3] Thus the discoveries that vitamin D cannot be so easily or readily obtained except by sun exposure, and that vitamin D is significant in fighting cancer, even skin cancer, fit well into the Catholic understanding of a designed reality. Note, that understanding does not require that sun exposure be overall more beneficial than not, it simply allows for it, and explains the why of it, should research continue to trend that way. For this is the realm of philosophy and of theology, not science. Science tells us what happens, and answers "why?" only so far as simple causality can explain. Philosophy and theology answer the deeper "why?" questions, the ones the young children ask, the ones we all, at some point, or in some sense ask, "why should this be the way it is?", things that are reasons for living and caring, explanations for wonder and awe. Design also explains the underdeveloped nature of other vitamin D pathways. The Creator, designing us to come to know Him, may well have found it advisable to make it hard for us to isolate ourselves in our own creation, our own artificial worlds. Or perhaps He created us best fit to survive to create the technology we would have today and in the future. Either way, we would be no less the products of a rational plan that any of us ourselves might have envisioned. You can see the scientist compromising his designs to survive the liftoff to outer space, creating things far stronger than space travel requires, and trading off space and weight (harder to accelerate out of the Earth's gravity well), with durability and function. You see the animal breeders compromising "perfection" of the desired form with the ability of the animal to survive disease. These limited cases demonstrate the sort of compromise even an omnipotent Creator might have chosen to make, remember that He did not intend for us to last forever as we are.
From the evolutionary standpoint, this is also neither exceptional nor required. For evolution, it is Darwinist senses, is no less philosophy than the Catholic understanding, and no more scientific than it (why I assert this is a matter for separate debate). In evolutionary speak, the person who was able to use the energy of the sun to combat its harmful effects (by creating vitamin D), would have an advantage over the one who could not. This would be a slight advantage perhaps, coming only in the form of longer lifespans after children had already started to bless (reverting momentarily to my own Faith in calling children a "blessing") the couple. Still, the longer lifespan would be used to have more children, to raise those children the couple has, to give them more and better, and thus give them an advantage over the children with parents who had not that genetic advantage. Over sufficient generations, if evolutionary theory is accurate, this should have been sufficient to instill in humanity a built-in safe guard for sun exposure, and similarly, working in the sun as they did, no other method for vitamin D absorption would have been necessary (they would have had far more than 15 minutes a day each day), and so would be under-developed.
Both then can explain this; both then might even have expected it. Which is simpler? Length to explain each is no judge of that, for my own bias comes in there, my own ability to articulate as well. Further, it is easy to see how one might spend longer on a simple topic (say division) not because it is inherently complex, but because it is inherently foreign to the listener, and that is at least partially responsible for my own motivation. In the end, the question of which is simpler, like that if which is more true, is something each must decide for himself.
[1]
http://abcnews.go.com/Health/Sun/wireStory?id=781896
[2]
Romans 8:20-21 http://www.usccb.org/nab/bible/romans/romans8.htm
[3] St. Augustine somewhere or another.