While ubiquitous in nature, melanin, which provides the coloring found in hair, skin, eyes, feathers, scales, etc., is an especially important substance as far as the human condition is concerned. Melanin’s role in determining skin color makes it the primary physiological basis for racial differentiation among humans; in fact, entire civilizations have arisen and fallen due to perceptions and misperceptions concerning its nature and signification.
It is for this reason that we have chosen to focus on melanin’s lesser known, biological role and how being more pigmented, i.e. darker skinned, or put oppositely, being less intensely de-pigmented, i.e. less light skinned, may have a unique set of health benefits which have been repressed or misrepresented over the course of history, in order to fuel race-based constructs.
Melanin, after all, has a diverse set of roles in various organisms. From the ink of the octopus, to the melanin-based protective colorings of bacteria and fungi, melanin offers protection against a variety of threats: from predators and similar biochemical threats (host defenses against invading organisms), UV light, and other chemical stresses (i.e. heavy metals and oxidizing agents). Commonly overlooked, however, is melanin’s ability to convert gamma and ultraviolet radiation into metabolic energy within living systems.
Single-celled fungi, for instance, have been observed thriving within the collapsed nuclear reactor at Chernobyl, Ukraine, using gamma radiation as a source of energy. Albino fungi, without melanin, were studied to be incapable of using gamma radiation in this way, proving that gamma rays initiate a yet-unknown process of energy production within exposed melanin.
Vertebrate animals, in fact, may convert light directly into metabolic energy through the help of melanin. In a review on the topic published in 2008 in the Journal of Alternative and Complementary Medicine, titled "Melanin directly converts light for vertebrate metabolic use: heuristic thoughts on birds, Icarus and dark human skin," Geoffrey Goodman and Dani Bercovich offer a thought-provoking reflection on the topic, the abstract of which is well worth reading in its entirety:
Pigments serve many visually obvious animal functions (e.g. hair, skin, eyes, feathers, scales). One is 'melanin', unusual in an absorption across the UV-visual spectrum which is controversial. Any polymer or macro-structure of melanin monomers is 'melanin'. Its roles derive from complex structural and physical-chemical properties e.g. semiconductor, stable radical, conductor, free radical scavenger, charge-transfer.
Clinicians and researchers are well acquainted with melanin in skin and ocular pathologies and now increasingly are with internal, melanized, pathology-associated sites not obviously subject to light radiation (e.g. brain, cochlea). At both types of sites some findings puzzle: positive and negative neuromelanin effects in Parkinsons; unexpected melanocyte action in the cochlea, in deafness; melanin reduces DNA damage, but can promote melanoma; in melanotic cells, mitochondrial number was 83% less, respiration down 30%, but development similar to normal amelanotic cells.
A little known, avian anatomical conundrum may help resolve melanin paradoxes. One of many unique adaptations to flight, the pecten, strange intra-ocular organ with unresolved function(s), is much enlarged and heavily melanized in birds fighting gravity, hypoxia, thirst and hunger during long-distance, frequently sub-zero, non-stop migration. The pecten may help cope with energy and nutrient needs under extreme conditions, by a marginal but critical, melanin-initiated conversion of light to metabolic energy, coupled to local metabolite recycling.
Similarly in Central Africa, reduction in body hair and melanin increase may also have lead to 'photomelanometabolism' which, though small scale/ unit body area, in total may have enabled a sharply increased development of the energy-hungry cortex and enhanced human survival generally. Animal inability to utilize light energy directly has been traditionally assumed. Melanin and the pecten may have unexpected lessons also for human physiology and medicine.
If the authors are correct, a longstanding assumption that animals are incapable of utilizing light energy directly is now called into question. In other words, our skin may contain the equivalent of melanin "solar-panels," and it may be possible to "ingest" energy, as plants do, directly from the Sun. We already know that sunlight exposure can reduce the risk of over 30 diseases, and that its primary metabolite in our skin, vitamin D, may reduce the risk of over 200.
Our biological connection and dependence to the sun, in fact, is so profound, that the very variation in human skin color from African, melanin-saturated dark skin, to the relatively melanin de-pigmented, Caucasian lighter-skin, is a byproduct of the offspring of our last common ancestor from Africa (as determined by mitochondrial DNA) migrating towards sunlight-impoverished higher latitudes, which began approximately 60,000 years ago. In order to compensate for the lower availability of sunlight, the body rapidly adjusted, essentially requiring the removal of the natural "sunscreen" melanin from the skin, which interferes with vitamin D production; vitamin D, of course, is involved in the regulation of over 2,000 genes, and therefore is more like a hormone, without which our entire genetic infrastructure becomes destabilized.
While a life-saving adaptation, the loss of melanin likely has adverse health effects, which include losing the ability to convert sunlight into metabolic energy, increased prevalence of Parkinson's disease (which involves de-melanization of the substantia nigra), and others effects which have yet been investigated in any detail. For now, it is important to point out that within the span of only 60,000 years (a nanosecond in biological time), many of the skin "color" differences among the world's human inhabitants reflect how heavily genetically-conserved was the ability of the human body to produce vitamin D. Furthermore, the trade-off involved in maintaining the ability create enough vitamin D within a sunlight-deprived clime by sacrificing melanin may have had adverse health effects that are only now being realized.