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Colour Variation In Humans,[object Object],And what lead to it,[object Object]
Origin of Humans,[object Object],The first people of the genus Homo (that we belong to) originated in Africa.,[object Object],They had quite dark skin colour, as it is known from scientific studies and examination of fossil remainds.,[object Object],But what lead to other skin colours developing? ,[object Object]
Different parts of the world receive different amounts of UV radiation, which is both beneficent and harmful for humans. ,[object Object],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).,[object Object]
Melanin is a pigment that occurs in people, and it acts as a natural biological shield against excess UV rays.,[object Object],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.,[object Object]
People with darker skin colours have higher melanin pigmentation, and are better protected from UV radiation.,[object Object]
However, humans quickly began to spread across the world, moving to regions with lower levels of UV radiation.,[object Object],The high melanin pigmentation resulted in smaller amounts of vitamin D received, which could lead to health issues.   ,[object Object]
…such as rickets and other bone diseases. ,[object Object]
Lighter skin with less melanin pigmentation allows more UV rays through, and receives more vitamin D than darker skin would in the same conditions.,[object Object]
Melanin-related mutations occurred, resulting in variousskin colours linked to melanin levels. ,[object Object],Depending on amount of UV radiation received population groups gained different skin colours in different parts of the world.,[object Object],The skin colours distribution map corresponds to the UV radiation map.,[object Object]
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.,[object Object],!,[object Object],Dark-skinned people can suffer from vitamin D deficiency when they move to regions with smaller UV radiation.,[object Object],People in the highlighted region have developed an ability to tan easily, which keeps their vitamin D and folate balanced during    	different seasons.,[object Object]
Melanin related mutations still occur today, an example of which is the Albino mutation.,[object Object],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’.,[object Object],If lacking pigmentation in the eyes, an albino’s  eyes appear red or purple.,[object Object],About 1 in 17,000 human beings has some type of albinism, although up to 1 in 70 is a carrier of albinism genes.,[object Object]
Hair colour also depends on amounts of melanin pigmentation. Generally, the more melanin there is, the darker the hair is.,[object Object],However, this can change over time leading to a change in colour (such as grey hair as a person ages),[object Object],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.,[object Object]
The graph shows that there are more light-haired people (with less hair pigmentation) in northern parts of Europe than in southern.,[object Object],Northern parts of Europe receive less UV radiation.,[object Object]
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.,[object Object],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.,[object Object]
Again, due to lower levels of melanin pigmentation northern Europe has higher light eye distribution than the south.,[object Object],Light eye colours include grey, blue and green.,[object Object],In the world, the most common eye colour is brown and the rarest is green.,[object Object]
By using the melanin pigmentation information you can judge about how well you are adapted to a particular climate.,[object Object],The End,[object Object]

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