Changes

== Contemporary theories ==

== Contemporary theories ==

=== Melanin vis-a-vis varna ===

=== Melanin vis-a-vis varna ===

<p style="text-align:justify;">Melanin is produced by melanocytes in a process called melanogenesis. Melanin is made within small membrane–bound packages called melanosomes. As they become full of melanin, they move into the slender arms of melanocytes, from where they are transferred to the keratinocytes. Under normal conditions, melanosomes cover the upper part of the keratinocytes and protect them from genetic damage. One melanocyte supplies melanin to thirty-six keratinocytes according to signals from the keratinocytes. They also regulate melanin production and replication of melanocytes.<ref name="ref8">Jablonski, Nina (2012). Living Color. Berkeley, Los Angeles, London: University of California Press. ISBN 978-0-520-25153-3.</ref>Individuals have different skin colours mainly because their melanocytes produce different amount and kinds of melanin. The genetic mechanism behind human skin colour is mainly regulated by the enzyme tyrosinase, which creates the colour of the skin, eyes, and hair shades.<ref name="ref9">Sturm, R. A. (2006). "A golden age of human pigmentation genetics". Trends in Genetics. 22 (9): 464–469. doi:10.1016/j.tig.2006.06.010. PMID 16857289</ref>^{<ref name="ref10">Sturm, R. A.; Teasdale, R. D.; Box, N. F. (2001). "Human pigmentation genes: Identification, structure and consequences of polymorphic variation". Gene. 277 (1–2): 49–62. doi:10.1016/s0378-1119(01)00694-1. PMID 11602344</ref>}Differences in skin colour are also attributed to differences in size and distribution of melanosomes in the skin.<ref name="ref11">Jablonski, Nina (2012). Living Color. Berkeley, Los Angeles, London: University of California Press. ISBN 978-0-520-25153-3.</ref>Both the amount and type of melanin produced is controlled by a number of genes that operate under incomplete dominance.<ref name="ref12">Schneider, Patricia (2003). "The Genetics and Evolution of Skin Color: The Case of Desiree's Baby". RACE—The Power of an Illusion. Public Broadcasting Service. Archived from the original on 6 May 2015. Retrieved 14 April 2015.</ref> One copy of each of the various genes is inherited from each parent. Each gene can come in several alleles, resulting in the great variety of human skin tones.</p>

<p style="text-align:justify;">Melanin is produced by melanocytes in a process called melanogenesis. Melanin is made within small membrane–bound packages called melanosomes. As they become full of melanin, they move into the slender arms of melanocytes, from where they are transferred to the keratinocytes. Under normal conditions, melanosomes cover the upper part of the keratinocytes and protect them from genetic damage. One melanocyte supplies melanin to thirty-six keratinocytes according to signals from the keratinocytes. They also regulate melanin production and replication of melanocytes.<ref name="ref8">Jablonski, Nina (2012). Living Color. Berkeley, Los Angeles, London: University of California Press. ISBN 978-0-520-25153-3.</ref>Individuals have different skin colours mainly because their melanocytes produce different amount and kinds of melanin. The genetic mechanism behind human skin colour is mainly regulated by the enzyme tyrosinase, which creates the colour of the skin, eyes, and hair shades.<ref name="ref9">Sturm, R. A. (2006). "A golden age of human pigmentation genetics". Trends in Genetics. 22 (9): 464–469. doi:10.1016/j.tig.2006.06.010. PMID 16857289</ref>^,<ref name="ref10">Sturm, R. A.; Teasdale, R. D.; Box, N. F. (2001). "Human pigmentation genes: Identification, structure and consequences of polymorphic variation". Gene. 277 (1–2): 49–62. doi:10.1016/s0378-1119(01)00694-1. PMID 11602344</ref> Differences in skin colour are also attributed to differences in size and distribution of melanosomes in the skin.<ref name="ref11">Jablonski, Nina (2012). Living Color. Berkeley, Los Angeles, London: University of California Press. ISBN 978-0-520-25153-3.</ref>Both the amount and type of melanin produced is controlled by a number of genes that operate under incomplete dominance.<ref name="ref12">Schneider, Patricia (2003). "The Genetics and Evolution of Skin Color: The Case of Desiree's Baby". RACE—The Power of an Illusion. Public Broadcasting Service. Archived from the original on 6 May 2015. Retrieved 14 April 2015.</ref> One copy of each of the various genes is inherited from each parent. Each gene can come in several alleles, resulting in the great variety of human skin tones.</p>