Viewing the Human Body as a Solar Power Device

In June 2006 I traveled from the campus of Arizona State University to the Institute of Noetic Sciences in Petaluma, California for a conference on Integral Life Practice through Ken Wilber's Integral Institute. I wrote an essay and got a partial scholarship to attend, which made me very excited.

One of the women I met there named Sofia Diaz really shocked me with some amazing information. I haven't been able to investigate what she told me because I can't find any information online about it -- I'm wondering if the Evoke Agents can help! Sofia Diaz said that there are photo receptor cells, just like the photo receptors that funnel photons in our visual system, IN OUR SOLAR PLEXUS!!!

Sofia Diaz is an internationally-acclaimed instructor who spent 20 years in India learning a particular form of sacred dance. Somehow I think what she said is important and relevant to my Imagine1 blog, which envisions a world in which latent capacities of human physiology catalyze the future of global social innovation.

Does anyone know anything about how this actually works?

I recently listened to a lecture from the Arizona State University Darwinfest by Nina Jablonski regarding the evolution of skin color. http://darwin.asu.edu/podcasts.php#jablonski Basically the human body is genius. We modulate the amount of vitamin D we get from sunlight, and we also modulate the amount of folic acid we produce, through skin coloration. Folic acid is crucial in embryonic development, and this is the true history of the importance of skin coloration. For me, Jablonski underscores the trend I am seeing that leads to what I call the transition from the Lesser to the Greater Anthropocene epoch: uncovering the hidden secrets of human physiology. Jablonski's work is a complete antidote serum for any form of racial prejudice. Since the transcript is in the public domain, I'll attach it here, so you don't have to download the podcast -- you can just read it.

Nina Jablonski: [0:53] Thank you, Mark, for that very nice introduction, and thank you also, and thank you, Peggy Coulombe, and the other organizers of the ASU Darwin Fest for inviting me here.

[1:04] It’s a delight to be here. I was on this campus talking to a group of graduate students and faculty three years ago and I found the campus a vibrant and wonderful place to be. I think you’re very lucky all to be here. I know that you’re suffering some financial difficulties right now, but I think if any university can get through it, ASU can. So, thank you for your invitation.

[1:28] Today, you know, we are getting really close to Darwin’s birthday. I study the evolution of human skin and skin color, so, what better thing to talk about than Darwin’s birthday suit. Something that certainly wasn’t talked about in his time, it was far too sensitive a topic, to talk about someone’s birthday suit, they probably didn’t even use that set of terms. But I think it’s a fun title for an important subject.

[1:57] Today I’m going to talk mostly about the evolution of skin pigmentation, although I’m interested in all aspects of the evolution of skin. It’s an important topic because skin pigmentation is one of the most conspicuous ways in which people vary, and in which groups of humans have been classified over the years, and so our understanding of it is so fundamental to our understanding of why we look different, and why people may have been treated differently on the basis of skin color. So, I hope today that we can begin to unfold together a very interesting and important evolutionary story that affects all of us fundamentally, in our health and in our social interactions.

[2:44] As Mark mentioned, Darwin was born nearly 200 years ago to the day. He was born a lightly pigmented baby in southern England, in Shrewsbury, in the south of England, and what he didn’t realize at the time and perhaps even his parents didn’t, is that he was born a very lightly pigmented baby in a mostly moderate to darkly pigmented world of people.

[3:15] Now Darwin lived a privileged life. As a young man he had a very good upbringing, very healthy, a very good education, and in his twenties he had the extraordinary opportunity to take a voyage from 1831 to 1836, nearly five years duration, on the ship, the Beagle.

[3:38] This epic journey took him to many, many places. This map shows you the long, circuitous, global journey that he took over nearly five years. During which he acc**ulated tremendous numbers of observations of variation in plants, animals and humans. We think about Darwin writing, especially in his early days, on variation in plants and animals, but he also made some observations of humans during the course of his travels.

[4:14] In his notebooks that he made during the voyage of the Beagle, he talks about how people in different places are built, what the color of their skin is, what the overall impression of their cultures is. By the time he actually sat down to begin writing his thoughts that would ultimately result in the omni "Origin of Species," he had a very good idea of what humans looked like.

[4:44] When he put his own observations together with observations gleaned from many other explorers before his time, he recognized that people existed throughout the world in a variety of different hues of skin color. And there were many people who were similarly pigmented to himself, fair or moderately pigmented, and that there were many other peoples who were very darkly pigmented.

[5:16] What is so interesting about Darwin’s writings is that he actually fails to make a connection between skin pigmentation and climate. And he fails to make a connection between skin color actually being an adaptation forged by the mechanism of natural selection that he brought to light in the world.

[5:44] So, it is a very interesting part of Darwiniana that actually Darwin observed variations of skin color. He actually observed that there was a difference between people at different latitude. Darker people were concentrated more close to the equator, lightly pigmented people closer to the poles, but he still did not bring the story of evolution to skin color. He knew from records of explorers and maps similar to this that there existed this distribution of skin pigmentations; darker near the equator, lighter near the poles.

[6:23] And so, it’s most curious. It’s famous that in his "Origin of Species" of 1859 Darwin devoted but one line to human evolution: light will be thrown on the origin of man and his history. All of his observations that he had about human variation, most of them fairly casual but still extensive, went unrecorded in his 1859 work.

[6:53] It wasn’t until much later in "The Descent of Man" in 1871 that he begins to tackle the wh*** topic of human variation, including variation in skin color. But, as I said, he does not, even though he says of all the differences between the races of man the color of the skin is the most conspicuous and one of the most marked. He goes on to say: these differences do not coincide with corresponding differences of climate.

[7:25] That’s very curious. He cites some anthropologists who had made observations that, basically, indicated that skin color was not related to levels of sunshine or humidity and he simply ceded to authority.

[7:42] He decided that his own observations for whatever reason perhaps weren’t good enough to warrant the assumption of evolution in the human condition. Or, perhaps, he backed away for some other social reason. We really don’t know why he backed away from making this correlation which he himself could observe.

[8:08] Today, I want to start out with this and show you how, at least, in this particular regard Darwin’s conclusion was in error and that we know now as a result of a variety of simple studies correlating human skin color with levels of ultraviolet radiation and other physical parameters as well as genetic studies on skin pigmentation genes that skin pigmentation represents one of the best examples of evolution working on the human body.

[8:47] Had only Darwin had NASA. In its many exploratory satellite missions, NASA has launched a series of total ozone mapping satellites that have allowed the ozone layer to be monitored. And also ultraviolet radiation levels at the earth’s surface to be monitored. What we did was take data from the TOMS seven satellite series, a collection of eight years of data points from the late 80s and early 90s, and we translated this into a single summary map.

[9:32] This is a map of annual average ultraviolet radiation at the earth’s surface that was taken from this large assembly of data points. What’s interesting here, you can pretty much figure out what this is all about by looking at the shades of violet. The most intense pinks and reds and deepest violets are the highest levels of ultraviolet radiation, mostly concentrated right around the equator. The incrementally cooler shades are the lower levels of ultraviolet radiation near the poles.

[10:09] There are a few significant things to look at here. Firstly that there’s a greater heterogeneity. Basically, ultraviolet radiation is related to latitude, but that there are areas outside of the equator that still have very high UV levels, such as parts of the Horn of Africa, here, fairly high in latitude, have very high UV levels because the air is so dry.

[10:37] Very high elevation areas, such as the Tibetan Plateaus have very high UV levels.

[10:44] The other thing to notice is that there’s a great bias in the distribution of land ma**** relative to ultraviolet radiation. So that we have a lot of the northern hemisphere that’s in very cool, low UV zones, and a lot of the southern hemisphere that receive a high amount of UV. And look. There’s no really corresponding area in the southern hemisphere to the far northern hemisphere.

[11:15] In other words, there’s no area equivalent to Northern Eurasia, Greenland and Northern Canada in the southern hemisphere. This bias in the distribution of land ma**** and ultraviolet radiation has had a fundamental effect on the evolution of skin pigmentation in humans.

[11:37] Now let’s look at what actually happens when ultraviolet radiation comes to the earth’s surface, because it’s quite interesting. Ultraviolet radiation, of course, isn’t all created equal. There’s some very energetic wavelengths, the shortest wavelengths of UVC, that are intercepted completely by the ozone layer and atmospheric oxidants. So under normal circ**stances they never penetrate down to the earth’s surface at all.

[12:06] UVB is also very energetic, but some of it penetrates down through the atmosphere. And if we simulate the situation at the equator, at either the vernal or autumnal equinox, which is depicted here, we can see this UVB passing, some of it being intercepted at the ozone layer, but some of it still passing through and having a profound biological effect.

[12:36] UVA, the least energetic but most plentiful species of UV, pa**** through the atmosphere pretty much unimpeded. And at the equator you get a tremendously high load of UVA. And just a smaller amount, but biologically significant amount, of UVB.

[12:55] This is very important, because these two types of UV have specific harmful and one specific positive effect on the physiology of animals, including ourselves. UV is pretty much a universally maligned influence in that it damages DNA, it creates other molecules that damage DNA, and it disrupts cell membranes. It disrupts lots of cellular processes.

[13:30] It is basically one of the most destructive, and yet ultimately creative forces in evolution because so much of biotic life over the last two billion years has evolved to basically tolerate high levels of ultraviolet radiation falling on the earth’s surface. So we think of it as a very negative force, but it’s actually been an incredibly important creative force in evolution.

[13:55] The one good thing that ultraviolet radiation does, as far as we’re concerned, is ultraviolet B, this relatively small fraction that gets through the atmosphere, fairly energetic, although it does do harm to DNA, it has the benefit of being able to bring about the initiation of vitamin D production in skin.

[14:20] And it does this in the skin of all terrestrial vertebrates, whether you’re a lizard, whether you’re a chicken, whether you are a human being, you are going to be making vitamin D in your skin when UVB impacts the surface of the skin and interacts with ch***sterol-like precursors in the skin. Vitamin D turns out to be phenomenally important to your normal physiology; yours and every other vertebrate animal’s physiology, for reasons that I’ll get into shortly.

[14:55] So we have this really mixed relationship, this schizoid relationship with UV. It’s basically a horrible entity, against which the biotic world has evolved many, many structures and physiological mechanisms to combat it. And then the one benign influence, in fact, extremely beneficial influence, making of vitamin D is something that we actually require and count on.

[15:23] UV falls on the earth in different percentages and it penetrates the skin to different depths. UVC, again, doesn’t really make it, under most conditions, through the atmosphere. UVB, that potentiates or catalyzes production of vitamin D penetrates just a tiny bit through the superficial layer of the epidermis of the skin into the upper part of the dermas, and there catalyzes the production of vitamin D. So it penetrates a little bit and does quite a bit of good.

[16:03] UVA is a pretty universally malign type of UV. It’s plentiful in the sunshine. In Arizona you get heaps of UVA throughout the year. And it penetrates the atmosphere and it penetrates the skin very deeply, causing a variety of different problems to DNA and also causing damage to connective tissues, ultimately leading to wrinkling and skin cancer. So it’s not a very good entity.

[16:36] What we realize in our studies of human skin pigmentation is that when humans evolved naked skin, and this we estimated to be around one and a half to two million years ago, that at the same time they would have had to evolve a mechanism to protect that mostly-naked skin from damage from ultraviolet radiation. And recall that the human ancestors that we’re talking about are living in equatorial Africa, in very, very high UV environments.

[17:19] Primates, all primates, have the ability to make melanin, the pigment melanin in their skin. Melanin is a really beautiful, interesting biological molecule. It’s one of these things that we love to talk about in evolution, because it’s been used over and over and over and over and over again. When you study evolutionary biology, you realize how little is new. When evolution comes upon something that works, a molecule like melanin that serves as a superior sunscreen, it’s used over and over and over again. There aren’t new ones that are invented. The old ones are simply brought out.

[18:00] What we see in the evolution of primates, in many lineages, is that when primates are subjected to equatorial high UV conditions, they evolve highly melanized, melanin enriched skin. When we evolved mostly naked body skin, our melano sites, our melanin producing cells developed mutations that led to a permanent high level of melanin pigmentation. And geneticists have actually been able to estimate that this happened probably no later than about 1.2 million years ago, and probably before.

[18:48] So when we think about the earliest members of our own lineage, the genus h***, we can think about people looking not too differently from these folks on the screen, having mostly naked bodies with some tufts of hair in a few strategic and important places, and the rest of the body being bereft of hair, but protected from the exigencies of ultraviolet radiation by melanin.

[19:25] This is a remarkable, but unremarkable phenomenon at the same time. It’s remarkable in that the genetic variant to produce permanently melanized skin occurred and was adopted in the human lineage, this was remarkable and important. It’s unremarkable in that it happened in many lineages under the same conditions. And we had, in vertebrate biology, this wonder melanin compound, this complex polymer that is so good at doing the sunscreen job.

[19:59] Melanin chemistry is fascinating, and I won’t go into details. But suffice it to say it’s a good molecule for sunscreen because it absorbs and scatters ultraviolet radiation as well as visible light, and it has the ability to chemically neutralize some of the free radicals that are produced when ultraviolet radiation and ionizing radiation impinge on the skin. So it’s like this incredible sort of physical absorber and scatter and chemical sponge at the same time. It’s really cool.

[20:32] And if you look at all the organisms around you in this room and organisms around you in nature, you’ll see melanin everywhere. Nearly ubiquitous.

[20:42] So darkly pigmented skin evolved under high-UV regimes and it evolved for two major reasons, as far as we can tell. I think one reason is probably more important than the other. The first reason is that melanin physically protects DNA from being broken down. We know that the rate of DNA destruction by ultraviolet radiation is greatly slowed by the presence of melanin, especially near the surface of the skin.

[21:17] The second reason that melanin is so marvelously protective and important is that it prevents the breakdown of a very important molecule that circulates in our bloodstream, and that is the B vitamin folate. Folate is an entity that we derive when we eat leafy vegetables and citrus fruits and wh*** grains. It’s a very important nutrient that is critical in the biosynthesis of DNA. And what do you need DNA for? You need DNA to make new cells.

[21:49] If you don’t have folate in your body, you can’t make DNA, you can’t make new cells. When do you need to make new cells in your body? All the time. You’re making new cells right now. But if you’re pregnant, you’re making a lot of new cells, in your embryo or fetus. If you’re a male, you’re making a lot of DNA in the young sperm in your testicles. So you need folate to fuel this wh*** process.

[22:18] Interesting about folate that it breaks down in the presence of ultraviolet A and long-wavelength ultraviolet B. So the presence of melanin in the skin protects against damage to DNA, and it protects against the breakdown of folate in circulating capillaries of the bloodstream. Two extremely important functions, the latter being far more important for reproductive success.

[22:51] And just to show you here, visually, this is you, in your very early days of an embryo, 21 to 25 days, during which your neural tube, the primordium of your brain and spinal cord is forming. You’re just a tiny, weenie little thing here, less than a centimeter in diameter at the beginning of this process. And what is very important in the early formation of the neural tube, is that cell division and fusion of the neural folds must occur very quickly, and under precise timing.

[23:31] Any problem in cell division causes this process to go either slightly or more severely awry, resulting in a neural tube defect of some level of severity. Some of these can be very minor, others of them can be fatal, and lead to immediate terminations of a pregnancy. If folate levels are altered or if there is a marked folate deficiency, this process of neural tube fusion is interrupted, sometimes seriously.

[24:04] And the key insight that allowed us to make this inference about the importance of UV on folate on reproductive success, had to do with the discovery in the late 1980s and early 90s, that folate deficiencies contribute to 70 percent of known neural tube defects at the time.

[24:27] So when we recognized that we had an agent, a physical agent, sunlight, UV, that damage something that was critical for reproduction, boing, here was the probable reason. The dark skin pigmentation had evolved. This was the direct connection between an environmental agent and reproductive success.

[24:51] Now humans, the earliest members of our lineage, evolved in equatorial Africa, but they didn’t stay there. We know that in the history of the genus h***, we have two major dispersal events. The first occurring probably nearly two million years ago, 1.8 to 1.9 million years ago, leading from equatorial Africa into what is generally known as the Middle East; India possibly via a coastal route into Southeast Asia and so forth.

[25:23] In other words, humans took it on their toes 1.8 or 1.9 million years ago, and dispersed out of the tropics, out of this intense ultraviolet regime, into areas that had a much different solar and climatic regime entirely. So what happened?

[25:42] Let’s look at what is happening, first, to the ultraviolet radiation. If we’re standing somewhere in the northern hemisphere, the UVC, again, is going to be interrupted completely by the atmosphere. The UVB, especially at the height of the winter and, for the most part, except for the height of the summer, the UVB is going to go as a cord through the atmosphere, and be completely dissipated without impacting the surface of the earth.

[26:18] This means that the potential for making vitamin D during most of the year in the far northern hemisphere is minimal or nonexistent. So even though sunlight may be plentiful, and even though UVA, the long-wavelength species may make it to the earth surface very well, there’s virtually no UVB getting to the earth’s surfaces. So humans moving out of the tropics are experiencing much lower levels of UVB; wonderful, great for our health. We get less damaging effects of UV.

[26:55] But what if you are dispersing out of Africa with darkly pigmented skin? Great built-in sunscreen is wonderful under intense regimes of solar radiation. It’s not a good idea if you’re living in a far northerly area with very attenuated levels of UVB. What we find is that melanin is such a good natural sunscreen, that it greatly slows the production of vitamin D.

[27:23] If two people are standing at any particular place where there’s a lot of UVB in the atmosphere; let’s say at the height of summer right here in Tempe. We have one person who’s darkly pigmented, one person who’s very lightly pigmented, it will take six times as long for the person with darkly pigmented skin to make vitamin D in their skin as the lightly pigmented person.

[27:48] So the natural sunscreen is great. It allows some vitamin D to be made, but the problem is made at more northerly latitudes and everything except the summer, vitamin D production is greatly attenuated, and almost impossible. This is a real problem. Having built-in sunscreen is great, but outside of the tropics, it’s all of a sudden not great.

[28:16] Let’s look at these UV levels again. They drop off dramatically. When we see these areas where we find some of the earliest dispersing human fossils, they’re up here in the sort of yellow, bordering on grey, zones. Some of them are in eastern Asia, in the sort of yellowish UV zones, moderate to low UV. And some of them are in high UV areas. So we know that early humans were dispersing into very low UV environments.

[28:45] We reasoned, even before there was genetic evidence, that there must have been evolution of de-pigmentation, of loss of pigmentation, in order for people to be able to live and reproduce in these biomes successfully. And since our first work on this subject, there have been myriad genetic studies that have demonstrated that, in fact, de-pigmented skin evolved multiple times as humans dispersed into high latitude and low UVB regimes.

[29:24] If you have darkly pigmented skin, these are the truly safe areas in which you can live year-round, where you don’t have to worry about making vitamin D in your skin. There will be enough UVB in the atmosphere that you can make vitamin D if you stand in these areas, very successfully. If you’re outside of these areas, or if you spend a lot of time indoors, you have greater difficulty. And you have to worry about where your vitamin D is going to come from. This is a long way of saying there was intense evolutionary pressure for loss of pigmentation.

[30:14] Now vitamin D, you’d think your mother told you all about vitamin D. If you’re of a certain age, she might have even made you take cod liver oil. Because she said vitamin D is really important to keep your bones strong. And, indeed, that is the most important, the best-known function, is that vitamin D permits absorption of calcium from the gut, and therefore allows you to build and maintain a strong skeleton. So that’s an extremely important function.

[30:48] But in the last 15 years, physiologists and biochemists have discovered that vitamin D is important for a cascade of other functions in the body, most notably for the maintenance of cell-mediated immunity for the maintenance of normal neuron health, there are vitamin D receptors all over the brain and spinal cord. And there are vitamin D receptors peppered through almost every organ of the body.

[31:15] In other words, vitamin D is necessary for the maintenance of normal homeostasis. And perhaps one of the most important functions is in the maintenance of a strong immune system, because we are beginning to recognize the correlation between long-term vitamin D deficiencies and chronic infectious diseases such as tuberculosis and even certain cancers: breast, colon, prostate and ovarian cancer have all been related to vitamin D deficiencies in every large epidemiological studies.

[31:51] So vitamin D is not just a simple, sort of one-note Samba. It’s a very complex vitamin, truly a hormone that has a cascade of important physiological effects. As I said, its role in the maintenance of skeletal health is probably its best known role. And serious vitamin D deficiencies result in this malady called nutritional rickets, which we thought was eradicated decades or, perhaps, even a hundred years ago.

[32:26] Sadly, it has not been eradicated, because there are many children throughout the world who do not get enough vitamin D because they are maintained inside or they don’t have enough vitamin D and calcium, so they never have a chance to make proper bones, and they suffer from nutritional rickets.

[32:46] This is a growing health problem among many communities in the world, especially darkly pigmented peoples living in low UV areas and working or living in regular houses, working in desk jobs, or wearing a lot of protective clothing. What was considered to be sort of an old-fashioned disease is very much with us in a matter of public concern.

[33:17] If you have very severe nutritional rickets as a female, you have a real problem with the deformation of your pelvis, so that you can’t give birth normally. A female with severe nutritional rickets has a very compressed pelvis, like this, and can’t give birth normally. It’s well-known that in the 19th century in the United States some of the first well-doc**ented caesarian section procedures were done on African American slave women who had no choice but to give birth via caesarian section. Their pelvis’ were so constricted by rickets that they couldn’t have a normal vaginal birth.

[34:02] So this is a severe problem, vitamin D deficiency can be a severe problem limiting reproductive success in the case of nutritional rickets and in a more sinister way in the long-term depression of immune system function.

[34:17] So de-pigmented skin evolved, and we see now wonderful genetic evidence, some of which uncovered by my colleagues at Penn State University in the last few years, indicating that genes mutations leading to de-pigmented skin in modern humans occurred twice, so that the ancestors of modern northern and northwestern Europeans had a particular mutation leading to de-pigmentation, and people then living in eastern Asia had another set of genes still to be completely determined, leading to their less-than-dark pigmentation.

[35:04] So this is really, really interesting, this work, because it shows that the selective pressure was really, really high. The variations existed, and these populations could then continue to disburse into ever more northern latitudes, armed with de-pigmented skin that would allow people to make vitamin D fairly easily.

[35:27] Not only in these ancestors of modern humans, but we also know via some absolutely superb genetic work done by a team in Leipzig, Germany, that Neanderthals also, at least some Neanderthals had the genetic for light pigmentation of their skins, as well as probably some of them having red hair. So this is fascinating. De-pigmented skin evolved at least three times independently in human history. This is a really, really interesting finding; something that we predicted just from the distribution of fossils, but that has now been reinforced by genetic data.

[36:15] We now are not, I’m saying the royal we, colleagues, I’m not a geneticist. I study the adaptations of humans to their environment. I’m really interested in the evolution of appearance and the external parts of our body. I wish I had to tools to actually do the genetic work, but I count on colleagues to do that.

[36:37] Now colleagues in India and in the United States and elsewhere, are looking at the possibility that deeply pigmented skin evolved more than once. And especially we’re looking at it in connection with the dispersal of people from northern into southern India. The population of India is very complex and heterogeneous and interesting. Some of the most ancient populations originated along the coast and are very darkly pigmented. But then there are many peoples who have northern Indian origins that migrated over the last several thousand years into southernmost India.

[37:21] They have reacquired dark pigmentation. So we’re trying to discover the genetic basis of this re-pigmentation phenomenon. It’s just as significant as the de-pigmentation. That depending on the environmental circ**stances, there are biological adaptations of the skin that are made, provided that the mutations, the genetic variance are present in the population to begin with.

[37:52] The grist of Darwin’s mill has to be there. You have to have a variation that can then be propelled forward by natural selection. This is so cool. Think about it. Light skin evolving more than once, dark skin evolving more than once. What does it mean?

[38:09] What does it mean for us putting people into different groups according to skin color? It doesn’t mean very much, does it? It has a great evolutionary significance in that it means that we adapted, that our ancestors were adapted to particular environments. But in terms of being a unique genetic trait that is present in only one group? Meaningless.

[38:33] What is beautiful about skin pigmentation, and I think Darwin would truly appreciate this, is that it is a great evolutionary compromise between the demands of protecting the skin against egregious damage from ultraviolet radiation in areas of high UV at the equator, and the need for making vitamin D in the areas of attenuated UVB closer to the poles; a wonderful double cline, or double gradient that exists.

[39:05] And so in a sense I’ve already addressed this by addressing my question to you about skin color and race, when we know that similar skin colors have evolved repeatedly in human history under similar environmental conditions, then skin color tells us a lot about the history of adaptation. It is not a unique signature of a particular genetic identity. So it’s a wonderful product of evolution. It is not a unique signature of race.

[39:39] Now humans have been on the move a lot, and I want to deal with a few interesting extreme cases that people often ask me about. One of the most interesting groups of people living in northern latitudes are the Sami people, the Laplanders, who, some of them live on the coast, some of them live in the hinterland, how do they make do? They’re living near the Arctic Circle. How do they get their vitamin D? They eat a lot of reindeer, and what do the reindeer eat, but a lot of vitamin D rich lichen.

[40:19] So the Sami people, themselves, eat the fat and the skeletal muscle that is rich in vitamin D that the reindeer have concentrated from the lichen. So the Sami are able to live quite happily and healthily, provided that they eat a lot of reindeer meat and fat.

[40:41] Why, many people ask me, do Inuit peoples, living in Alaska, the Aleutian Islands -- and the Chukchi peoples in northeastern Asia -- why do they have moderately or darkly pigmented skin? By right, they’re right at the Arctic Circle. No UVB. What’s going on here? Why is their skin moderately pigmented? Well you might get a good idea just from looking at the nature of their environment, and all of the reflected light and the reflected UVA coming off the surface of the snow and ice.

[41:21] Inuit and other people living in these, especially coastal environments, have to deal with extremely high levels of reflected UV coming up at them from below. And so we surmise that they have, in a sense, been able to maintain or even build up levels of tanning potential in pigment in part because they have a vitamin D rich diet. So they’re able to protect themselves from the reflected UV with moderately pigmented skins, as long as they get their vitamin D from their indigenous diets.

[42:04] What happens when Inuit abandon their aboriginal diets? They have vitamin D deficiencies in great numbers, and it’s one of the major public health problems in Alaska and Northern Canada. When they’re eating their aboriginal diets of marine mammal, especially marine mammal blubber, that is rich in vitamin D, as well as oily fish, they’re in great shape. When these traditional diets are abandoned, they have far more difficulties.

[42:37] Now humans have been on the move. We’re talking about Inuits who perhaps have been in their native environments for the last 10,000 or 12,000 years. But just in the last 5,000 and especially the last 500 years, humans have been moving at extraordinary rates, and over great distances. Within Africa we see a great dispersal of Bantu language speakers from high UV areas to low UV areas. Just since the era of exploration, in about the last 500 to 600 years, tremendous movements of people, all over the world.

[43:17] The ones that I’ve depicted here are voluntary movements that have involved large transgressions of latitudinal zones and UV regimes. But there have also been many involuntary movements.

[43:32] First, let’s think about the ramifications of these voluntary movements. Many lightly pigmented people now living in very sunny places, but I don’t have to tell you. I would guess lots of you visit the dermatologist.

[43:47] Especially those of you who are beyond the age of 30 make repeated visits to the dermatologist because even if you haven’t had bad sunburns you’ve had a lot of UV exposure, unprotected UV exposure resulting ultimately in many skin cancers.

[44:06] What we don’t know and what epidemiologists are just beginning to try to figure out is how much of this excess UV exposure actually resulted in folate deficiencies leading to birth defects. This is much more difficult to look at retrospectively, but it is possible to look at prospectively.

[44:32] What about the opposite -- darkly pigmented people living in low UV environments or darkly pigmented people being inside all the time and working desk jobs? Many people, from the Indian subcontinent and from Africa living in high latitude places with low UV, suffer increased incidences of nutritional rickets and other vitamin D deficiency diseases.

[45:00] In northern Europe and the UK public health attention has been focused on this now for a few decades. We’ve been much slower about it in the United States and Canada, but we’re beginning to realize this. The problem is exacerbated by cultural practices, such as widespread concealing clothing that prevent people from making vitamin D in the small areas of exposed skin. So, we see headlines like this: rickets on the rise, when one would think or one would hope that the disease had been eradicated.

[45:39] As I mentioned, people moved voluntarily but then there were huge movements of people involuntary associated with the trans-Atlantic slave trade resulting in over 12 and a half million people being trans-located from equatorial Africa often long distances into areas with very different UV regimes. This had enormous consequences for life in the Americas and life, actually, throughout the world. It had enormous social consequences that we deal with all the time in our social interactions.

[46:21] What we think less about are the health interactions, the health problems that have derived from this that I have indicated previously, that as soon as you take someone with a lot of natural built-in sunscreen and put them into a low UV environment they have chronic problems with vitamin D deficiencies.

[46:43] These now are being addressed in a variety of public health initiatives in this country. Even though we are slower than Europe, we are beginning to grasp the mettle and deal with this difficult biological issue.

[46:58] What does this mean in terms of our social interactions with one another? It means that we have to look at the history of interaction between people. The voluntary movement of people was one thing. The involuntary transportation of people was a wh***, different thing because people met are on very unequal social footings. And this lead to tremendously iniquitous meetings in which people were valued very differently, depending on whether they were seen as predators or prey.

[47:38] A very, very, very sinister history that we have to deal with in the last 500 years of human history since the trans-Atlantic slave trade began, and roughly 250 years since it ended. We’re still living with this legacy, but we can begin to deal with it by understanding the history of how these transportations occurred, and also by understanding the basic biology behind why we look different. These are small things, understanding deep evolutionary history and human history, but they do allow us to begin to propel human relations forward in a constructive way.

[48:31] And nothing more important has propelled us forward than the election and inauguration of a moderately pigmented African-American person with mixed ancestry. Now this is a very interesting example of someone who is a classic American hybrid, his parents, from different parts of the world, meeting in an American context and reproducing. He shares with other moderately pigmented people the fact that he’s able to produce a lot of melanin in his skin when he’s exposed to the sun, but when he’s out of the sun he has to worry about vitamin D deficiency. As I understand it, I think he’s going to spend a lot of time at his desk, and so he really should have some vitamin D supplement at his side, among many other things.

[49:33] All kidding aside, he does represent an important emblem of American society, a product of genetic mixture, and at one level everyone in this room is a genetic mixture. We just have to go far back enough in our tree to find out where our parents and grandparents, or great, great, great grandparents are from.

[49:57] So, I think Darwin would be very happy today to know about NASA data, to know all the things we know about the genetics of human skin pigmentation, because he would be able to rewrite those lines in "The Descent of Man" about the lack of relationship between skin color and climate. He would see that skin color is the product of evolution by natural selection, and I think he would find that profoundly satisfying. He would use, I think, this knowledge to help us deal with the problems of racism still abound in the world.

[50:34] I am a perpetual, perennial optimist that we can take our knowledge of human evolution, take our knowledge of human history, and just say isn’t this important for us to understand, let’s get on with it. Let’s get on with understanding each other as brothers and sisters, and understanding the history of social interaction that we have had to deal with as a species, especially for the last 500 years.

[51:06] To conclude, you have, right on your bodies, the best evidence for teaching about the theory of evolution by natural selection. Use this to great advantage, especially in this Darwin bicentennial year when people are talking about evolution and the evidence for evolution. You have the best evidence right on your bodies, especially if you have somebody next to you who has got a slightly different skin color, you can talk about the differences and how they evolved. You don’t have to look for fossil evidence and get a picture from the web or look for a bone or something, you’ve got it right there.

[51:46] Teach it, celebrate it, love it, and just relish that you are the products of evolution.

[51:53] [applause]

Announcer: This lecture is part of the Arizona State University Darwin Distinguished Lecture Series. It is sponsored by the ASU Office of the President, the College of Liberal Arts and Sciences, The School of Life Sciences, the Center for Biology and Society and is a production of Grassroots Studio