Sunburn (or erythema) is redness of the skin, which is due to increased blood flow in the skin caused by dilatation of the superficial blood vessels in the dermis as a result of exposure to UV radiation. 

High UV doses may also results in edema, pain, blistering, and peeling of the skin a few days following exposure. 

UV-B radiation is believed to be mainly responsible for sunburn as it is more erythmogenic by a factor of 1,000, however since there is more UV-A radiation reaching the earth’s surface, UV-A contributes 15-20% to the sunburn reaction in the summer months. 

Risk factors for sunburn include fair skin, red or blond hair, blue eyes, and freckles!

One of the chronic effects resulting from fair skin (light or white) repeated exposure to UV radiation is premature aging of the skin, which encompasses a number of clinical signs that reflect structural changes in the dermis. 

These clinical signs include dryness, wrinkles, accentuated skin furrows, sagging, loss of elasticity, and mottled pigmentation, and are the result of degenerative changes in elastin and collagen. 

The degenerative changes accumulate over time and are largely irreversible.

It is believed that as much as 80% of premature aging of the skin may occur within the first 20 years of life!

Suppression of the immune system resulting from exposure to UV radiation is believed to be an important contributor to the development of nonmelanoma skin cancers. Put simply, UV radiation induces a state of relative immunosuppression that prevents tumor rejection!

In comparison with white skin, the black skin stratum corneum is equal in thickness but more compact: about twenty cell layers are observed in blacks versus sixteen layers in whites; this makes the skin more durable!

The lipid content of black epidermis is also somewhat higher, and this perhaps explains the greater cellular cohesion, hence the difficulty in stripping off the black horny layer, but it also contributes to why black skin looks much younger than white skin the same age!

These findings could also explain a slightly inferior permeability of black skin to certain chemicals, which means darker skin is more resistant to external chemical exposure!

The primary factor contributing to the evolution of dark skin pigmentation was the breakdown of folate in reaction to ultraviolet radiation; the relationship between folate breakdown induced by ultraviolet radiation and reduced fitness as a failure of normal embryogenesis and spermatogenesis led to the selection of dark skin pigmentation. 

By the time modern Homo sapiens evolved, all humans were dark-skinned!!

There was a reason the first humans were dark skinned people... We were originally designed for this planet!

All that came after the original are mutations and the result of interbreeding with Neanderthal!

Humans with dark skin pigmentation have skin naturally rich in melanin (especially eumelanin), and have more melanosomes which provide a superior protection against the deleterious effects of ultraviolet radiation. 

This helps the body to retain its folate reserves and protects against damage to the DNA!

The global distribution of generally dark-skinned populations is strongly correlated with the high ultraviolet radiation levels of the regions inhabited by them. 

These populations almost exclusively live near the equator, in tropical areas with intense sunlight: Australia, Melanesia, New Guinea, South Asia and Sub-Saharan Africa. 

Studies into these populations indicates that dark skin is a retention of the pre-existing high UV adapted state of modern humans before the Out of Africa migration and not a later evolutionary adaptation.

Due to mass migration and increased mobility of people between geographical regions in the recent past, dark-skinned populations today are found all over the world and are the majority on the planet!

Dark-skinned humans have high amount of melanin found in their skin. 

Melanin is derivative of the amino acid tyrosine. 

Eumelanin is the dominant form of melanin found in human skin. 

Eumelanin protects tissues and DNA from radiation damage of UV light. 

Both UV-A & B!

Melanin is produced in specialized cells called melanocytes, which are found at the lowest level of the epidermis.

Melanin is produced inside small membrane-bound packages called melanosomes. 

People with naturally occurring dark skin have melanosomes which are clumped, large, and full of eumelanin.

A four-fold difference in naturally occurring dark skin gives seven to eightfold protection against DNA damage, but even the darkest skin color cannot protect against all damage to DNA!

But you have that advantage of protection if you do have darker skin!

Dark skin offers great protection against UV-R because of its eumelanin contect, its superb UV-R absorbing capabilites of large melanosomes, and because eumelanin can be mobilized faster and brought to the surface of the skin from the deeps of the epidermis.

For the same body region, light- and dark-skinned individuals have similar numbers of melanocytes (there is considerable variation between different body regions), but pigment-containing organelles, called melanosomes, are larger and more numerous in dark-skinned individuals.

Due to the heavily melanised melanosomes in darkly pigmented skin, it can absorb more energy from UV-R and thus offers better protection against sunburns and by absorption and dispersion UV rays. This is energy we naturally absorb!

Darkly pigmented skin protects against direct and indirect DNA damage!

Photodegration occurs when melanin absorbs photons. 

Recent research suggest that the photoprotective effect of dark skin is increased by the fact that melanin can capture free radicals, such as hydrogen peroxide, which are created by the interaction of UV-R and layers of the skin.

Heavily pigmented melanocytes have greater capacity to divide after UV-R irradiation, which suggests that they receive less damage to their DNA!

Although darkly pigmented skin absorbs about 30 to 40% more sunlight than lightly pigmented skin, dark skin does not increase the body's internal heat intake in conditions of intense solar radiation.... Like a high performance engine that just runs cooler!

Solar radiation heats up rather the body's surface and not the interior. 

Skin color is a polygenic trait, which means that several different genes are involved in determining a specific phenotype. 

Many genes work together in complex, additive, and non-additive combinations to determine the skin color of an individual. 

Skin color seems to vary mostly due to variations in a number of genes of large effect as well as several other genes of small effect (TYR, TYRP1, OCA2, SLC45A2, SLC24A5, MC1R, KITLG and SLC24A4). 

Dark pigmented people living in high sunlight environments are at an advantage due to the high amounts of melanin produced in their skin. 

The dark pigmentation protects from DNA damage and absorbs the right amounts of UV radiation needed by the body, as well as protects against folate depletion. 

Folate is water soluble vitamin B complex which naturally occurs in green, leafy vegetables, whole grains, and citrus fruits. 

Women need folate to maintain healthy eggs, for proper implantation of eggs, and for the normal development of placenta after fertilization. 

Folate is needed for normal sperm production in men. 

Furthermore, folate is essential for fetal growth, organ development, and neural tube development. 

Folate breaks down in high intense UV-R.

Dark-skinned women suffer the lowest level of neural tube defects.

Folate plays an important role in DNA production and gene expression. It is essential for maintaining proper levels of amino acids which make up proteins. 

Folate is used in the formation of myelin, the sheath the covers nerve cells and makes it possible to send electrical signals quickly. 

Folate is also plays an important role in the development of many neurotransmitters, e.g. serotonin which regulates appetite, sleep, and mood. Serum folate is broken down by UV radiation or alcohol consumption.

Because the skin is protected by the melanin, dark pigmented people have a lower chance of developing skin cancer and conditions related to folate deficiency, such as neural tube defects.

Dark skinned people must be aware without proper diet vitamin D deficiency can be a concern!

BUT FOR THE MOST PART YOU NEED TO UNDERSTAND... DARK SKIN IS NOT A CURSE!

DARK SKIN IS A GIFT!!!!!