PhotoperiodEffect.com

3. If all these many, many chronic illnesses are supposedly caused by light, why aren't there any immediately occurring, acute illnesses caused by using artificial lights as much as we do now? Just statistically, if there are so many consequences to extra light exposure, wouldn't you expect that more of the resulting illnesses would take hold quickly? Why the coincidence that all these illnesses are chronic illnesses which tend to show up after at least a decade, while none of them, along any causal pathways you speculate about, turn out to be immediate problems? How is this to be explained?

The answer may lie in our long experience of the seasons – something human beings have been exposed to for tens of thousands of years. We have evolved to cope well with a certain degree of change in the length of our days for months at a time because most human beings have had to deal with seasonal variation in the length of days. This experience of seasons began after we had discovered fire and begun to move into Europe, displacing Neanderthals from the more northerly regions of the earth which they were initially better adapted to and which were for hundreds of thousands of years had been their exclusive preserve. It may even be that, through interbreeding, we possess some Neanderthal DNA.

We have also doubtless adapted at least somewhat to the light from domestic fires themselves. The newly discovered sensors in our eyes that tell us when it is day or night, ipRGCs, do not react to longer frequencies such as the red or orange light from fires, or embers. Those of our ancestors who suffered most, and most immediately, from enduring longer days or nights died sooner and left fewer children. Else summer might make us all feel a little sickly. It necessarily follows that all the deleterious effects that follow from extending our days with artificial light will be chronic (even if of sudden onset when they eventually hit us, as with MS, or hay fever), and not acute illnesses that appear as soon as their cause. Creatures in northerly latitudes who couldn't take at least longer seasonal variations in stride, didn't tend to pass on their genes. Which is to say, very importantly, that logic tells us that we should reasonably expect the negative consequences from our modern extended days under artificial light to show up as chronic illnesses and not as acute illnesses.

The technology of candles and oil lamps has also undergone a gradual evolution and improvement over thousands of years, becoming more efficient, and therefore brighter, and therefore, giving off higher frequencies of light as more and more superior materials were burned, in more efficient ways. Argand lamps and whale oil were the pinnacle of oil lamp technology, providing brighter and whiter light than had ever been possible before. It has been possible to read for hours by the light of single candle, held close to a book, for a very long time – but to do so also disturbs the body-clock and melatonin rhythms, etc. This has been possible for a very small minority of human beings for some time now, and this too, may have helped adapt us, a little, to the erratic periods of light we now experience, through premature deaths among historical elites.

Of course, staying under constant light, day and night, including while we sleep suppresses melatonin so thoroughly that negative health consequences do show up fairly enough – but such conduct is very unusual and something doctors are willing to advise against. Behavior as extreme as never experiencing darkness seems sufficiently extreme and unnatural that we are willing to admit that it might have an effect on our health, yet somehow, even going so far as to halve the number of hours of darkness we experience (assuming we sleep an hour or two after the sun has risen) seems utterly benign to us – despite all the evidence piling up that it's not.

It should also be noted, that as our use of artificial light becomes ever more extensive, we are in fact seeing far more cases of very early onset diabetes, asthma, peanut allergies, obesity etc., etc. This alarming trend is much noted in current medical literature and newspaper reports as well. In other words, we are increasingly seeing diseases we once considered to be adult chronic illnesses occurring in children – including far more babies being born overweight with a high risk of being obese throughout their entire lives. Technically know as “anticipation of age of onset”, this increasingly early appearance of illness is a ubiquitous phenomenon across an astonishing range of diseases and disorders, including those we have assumed to be genetic illnesses, or partially genetic illnesses. It is very strong evidence for an environmental cause for these illnesses, and that that environmental cause is getting further out of control.

It might, according to this reasoning, be interesting to look for more acute or early onset illnesses (say more childhood diabetes or sooner onset) in the case of populations whose genes evolved closest to the equator. There are in fact such marked patterns and susceptibilities for African-Americans and others who encounter fully modern conditions for the whole span of their lives, but whose genes evolution might have shaped slightly differently, without having to worry about problems from seasonal variation in the length of daylight. Specifically, according to the New York Times, “African-Americans and Latinos, particularly Mexican-Americans and Puerto Ricans, incur diabetes at close to twice the rate of whites. .... Some Asian-Americans and Pacific Islanders also appear more prone, and they can develop the disease at much lower weights.” [http://nytimes.com/2006/01/09/nyregion/nyregionspecial5/09diabetes.html]

Hypertension is also higher in black (more equatorial) hispanics according to a study by Luisa N. Borrell, assistant professor of epidemiology at Columbia's School of Public Health in New York City in the February issue of Ethnicity & Disease. “"The idealized Hispanic health advantage disappears when race is accounted for. We are ignoring the real health profile of Hispanics," Borrell said in a prepared statement. Overall, blacks, regardless of their ethnicity, had the highest rates of high blood pressure, the study noted.” [“Study Looks at Hispanic Hypertension 'Race Gap'” Jan 29, 2006 [http://health.excite.com/article/id/530516.html]

The effect extends to lung cancer as well, according to a study “Among cigarette smokers, African Americans and Native Hawaiians are more susceptible to lung cancer than whites, Japanese Americans, and Latinos.” [16436765] (Note that nicotine simulates many of the effects of bright light after a period of darkness by increasing dopamine.)

Nor is it clear just how completely any human populations have adapted to greater seasonal variation or the more common presence of fire light in the last few tens of thousands, or hundreds of thousand years. By evolutionary standards one should most probably expect considerable, but perhaps imperfect adaptation to new conditions after such a relatively short period of Natural Selection. It would be interesting to know, for example, whether European populations have adapted to the far greater amount of seasonal cloud cover in Europe by shifting the frequency of light that the ipRGCs are most sensitive to toward less blueish or violet light (or more violet, to the extent that clouds preferentially allow the passage of ultraviolet light), or perhaps by limiting somewhat the degree of ”light competition”.