Can People Without Eumelanin Survive Climate Change?
Melanin may be a major component involved in adaptation to climate warming!
Why do people from different parts of the world have different colored skin? Why do people from the tropics generally have darker skin color than those who live in colder climates? Variations in human skin color are adaptive traits that correlate closely with geography and the sun's ultraviolet (UV) radiation. Climate change has a significant effect on skin color, as well as the overall temperature of our bodies. The higher the temperature, the more drastic changes occur to the skin's natural color. As the planet continues to warm, evolutionary changes are expected in most species — including Homo sapiens. Climate change will alter the internal workings of our bodies in subtle but significant ways and will cause a noticeable shift in our appearance.
As Earth gets hotter due to climate change, lighter-skinned people will not produce more melanin over time and become darker skinned. Instead through the mechanisms of natural selection those species including humans without the traits necessary for prolonged life will die out over time and see a reduction in birth rates. Heat is not the issue—it’s ability of the skin to absorb sunlight and vitamin D while blocking out solar radiation more likely to lead to cancer and other issues. And the operative event is natural selection—people whose skin color is more amenable to local climate will produce more offspring that survive. The evidence is that all homo sapiens were dark skinned initially, and that lighter skin provided advantages as human populations moved North into climates where sunlight was not a constant.
The ‘San people’ (called the ‘Kalahari Bushmen’ until recently, when the term was rightly thought of as perjorative). are in many ways a product of natural selection. They’ve lived in parts of Africa where being taller or heavier would be disadvantages relative to local climate. The ancestry didn’t ‘evolve’ darker skin—darker skinned people did better in a hot, humid and sunny African environment and thus left more offspring. Lighter-skinned people who moved into the San homeland would have significant challenges there from the heat and sunlight. And eventually after a few dozen generations, their descendants would be shorter and have darker skin because shorter, darker skinned humans would survive better in that environment. If biological protection from the increasing amounts of UV rays in a hotter world (assuming a hotter Earth receives larger amounts of UV radiation from the sun) is crucial for human survival, then yes people could become darker-skinned over time.
But that would only be because the lighter-skinned people died off and couldn’t reproduce, and so only the darker-skinned people were left. Not because an individual’s skin evolved to produce more melanin within their lifetime. Melanin on skin blocks near UV, affecting the nutritional balance. Near UV on skin produces vitamin D. The same UV on skin destroys folate, one of the vitamin Bs. Nutrition can provide both vitamin D and folate, but depends critically on diet. The deficiencies in the two vitamins can be lethal. Deficiency of vitamin D causes rickets. Rickets is a bone disease that kills. It especially kills young women in childbirth. Folate deficiency causes neural tube defects in newborns as well causing miscarriages.
There are several alleles on different loci that influence the amount of melanin in skin. The equilibrium mixture of alleles is set by the balance between rickets and folate deficiency. So artificial global warming will not have an easily predicted affect on skin color. Cold water dissolves less oxygen that warm water. Animals in the ocean require dissolved oxygen. So the quantity of fish and other organisms will decrease around the world. This not only includes cold water fish. This includes other animals with vitamin D, including shrimp. So again we are looking at a vitamin D shortage. If governments simultaneously decide to try to artificially block the sun that reaches the planet we would see a mass extinction that could encompass large human populations.
A lot depends on what the food available to people all over the world. Foods that have excess amount of vitamin D will make natural selection favor darker skin tone. Food that have an excess amount of folic acid with make natural selection favor lighter skin tone. Vitamin D is produced by the skin in response to exposure to the ultraviolet rays in sunlight; too little of the vitamin causes bone weakening and rickets and possibly contributes to many other chronic diseases including cancer. Small amounts of vitamin D can also be acquired by drinking fortified milk, eating fortified breakfast cereals or eating fatty fish such as salmon, tuna and mackerel, as well as from over-the-counter dietary supplements. It’s not clear exactly how many people may be deficient in the vitamin, experts believe about 30 to 40 percent of the United States population may be affected.
Homo Sapiens originated in Africa. They migrated north, and east and eventually spread out all over the globe. They were all black to start with. It was mutation that created white skin, the process of natural selection kicked in. So it happens that the darker hues are better at radiating heat. So in the hotter climes, losing heat faster can make a difference to survivability. More people with dark skin survived and procreated than those with lighter skin.
In colder climes, losing heat faster can kill you. So those archaic humans like the Neanderthal and Denisovan with lighter skin survived better during the ice age. When modern man the Sub-Saharan African came into Eurasia he impregnated archaic Neanderthal and Denisovan. Modern Europeans, Asians and Americans – but not Africans – inherited about 2%-10% of their genes from Neanderthals, with modern man the Africans apparently hooking up with their stocky cousins only after they moved out of Africa. Data indicates that a wave of modern humans left Africa approximately 200,000 years ago and this group interbred with Neanderthals. This ancient group of Europeans then migrated back into Africa multiple times over a millennia , introducing Neanderthal ancestry to North African, Arab and Asian populations.
Previous estimates suggesting that East Asians might have have approximately 20% more Neanderthal ancestry compared to Europeans, were wrong and humans on different continents had Neanderthal ancestry “surprisingly similar to each other.” Climate change is considered the greatest health threat of the 21st century. People living with disability, poverty, and unemployment are further structurally and disproportionately impacted by the projected devastating effects of climate change the most vulnerable populations include Persons with Albinism (PWA) whose health and well-being are impacted by the rising temperatures and increasing concentrations of greenhouse gases in the atmosphere!
Over several years, greenhouse gases that occur naturally in the atmosphere alongside the generation of greenhouse gas emissions by humans has led to increased warming of the planet. This human-induced climate change has led to greater temperature fluctuations and unpredictable and extreme weather events globally that ultimately impact the health and well-being of the world's population. For example, more recently in the United Kingdom, an extreme heat warning was issued because of a high temperature surge, unheard of in the past . With the average temperature of the world estimated to increase by as much as 2 °C , even people without eumelanin living in the Northern Hemisphere will be increasingly affected.
People without eumelanin living in the Southern Hemisphere will also experience even higher temperatures, which will make them even more affected by these temperature extremes. Furthermore, the planet is facing negative consequences from human-made deforestations and degradations . Many trees and other plant species, sustaining lives and livelihoods, are threatened to be extinct which decreases not only the resources for food and oxygen, but also shade from the sun, which is vital when outdoors. Earth is likely to cross a critical threshold for global warming within the next few years, and nations currently need to make an immediate and drastic shift away from fossil fuels to prevent the planet from overheating dangerously beyond that level, according to a major new report released on Monday.