Colour Variation In HumansAnd what lead to it

Origin of HumansThe first people of the genus Homo (that we belong to) originated in Africa.

They had quite dark skin colour, as it is known from scientific studies and examination of fossil remainds.

But what lead to other skin colours developing?

Different parts of the world receive different amounts of UV radiation, which is both beneficent and harmful for humans.

UV rays trigger off the production of vitamin D, but reduce amounts of folate (which is important for cell production and DNA synthesis, and particularly embryo development).

Melanin is a pigment that occurs in people, and it acts as a natural biological shield against excess UV rays.

As humans have originated from areas with high UV radiation, it was important to develop a melanin-rich pigmentation which would help them to survive.

People with darker skin colours have higher melanin pigmentation, and are better protected from UV radiation.

However, humans quickly began to spread across the world, moving to regions with lower levels of UV radiation.

The high melanin pigmentation resulted in smaller amounts of vitamin D received, which could lead to health issues.

…such as rickets and other bone diseases.

Lighter skin with less melanin pigmentation allows more UV rays through, and receives more vitamin D than darker skin would in the same conditions.

Melanin-related mutations occurred, resulting in various skin colours linked to melanin levels. Depending on amount of UV radiation received population groups gained different skin colours in different parts of the world.

The skin colours distribution map corresponds to the UV radiation map.

Light-skinned people are at a higher risk of folate deficiency and cancer than dark-skinned people when they are at regions with high UV radiation.

Dark-skinned people can suffer from vitamin D deficiency when they move to regions with smaller UV radiation.

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People in the highlighted region have developed an ability to tan easily, which keeps their vitamin D and folate balanced during

different seasons.

Melanin related mutations still occur today, an example of which is the Albino mutation.

An albino can either lack pigmentation in the eyes, hair and skin or have normal skin and hair colours which is lighter than their parents’.

If lacking pigmentation in the eyes, an albino’s eyes appear red or purple.

About 1 in 17,000 human beings has some type of albinism, although up to 1 in 70 is a carrier of albinism genes.

Hair colour also depends on amounts of melanin pigmentation. Generally, the more melanin there is, the darker the hair is.

However, this can change over time leading to a change in colour (such as grey hair as a person ages)

Hair colour can be generally associated with a person’s skin or eye colour, but due to globalisation and interaction between ethic groups there is more variation.

The graph shows that there are more light-haired people (with less hair pigmentation) in northern parts of Europe than in southern.Northern parts of Europe receive less UV radiation.

Eye colour too depends on melanin levels. An eye can have a solid or partial colouring. A person can also have two different coloured eyes.

Blue eye mutation is newer than brown eyes, and mostly occurs in Europe, but can be found in Asia. This suggests that blue eyed people are more closely related than people with dark eyes.

In the world, the most common eye colour is brown and the rarest is green.

Again, due to lower levels of melanin pigmentation northern Europe has higher light eye distribution than the south.

Light eye colours include grey, blue and green.

By using the melanin pigmentation information you can judge about how well you are adapted to a particular climate.

The End