Editing Human variability (section)

====Climate and disease====
Other important factors of environmental factors include climate and disease. Climate has effects on determining what kinds of human variation are more adaptable to survive without much restrictions and hardships. For example, people who live in a climate where there is a lot of exposure to sunlight have a darker color of skin tone. Evolution has caused production of folate ([[folic acid]]) from [[Ultraviolet|UV]] radiation, thus giving them darker skin tone with more melanin to make sure child development is smooth and successful. Conversely, people who live farther away from the equator have a lighter skin tone. This is due to a need for an increased exposure and absorbance of sunlight to make sure the body can produce enough [[vitamin D]] for survival.<ref>{{Cite web|url=http://humanorigins.si.edu/evidence/genetics/human-skin-color-variation/modern-human-diversity-skin-color|title=Human Skin Color Variation {{!}} The Smithsonian Institution's Human Origins Program|website=humanorigins.si.edu|access-date=2016-11-16|date=2012-06-20|archive-date=21 November 2016|archive-url=https://web.archive.org/web/20161121012901/http://humanorigins.si.edu/evidence/genetics/human-skin-color-variation/modern-human-diversity-skin-color|url-status=dead}}</ref>

Blackfoot disease is a disease caused by environmental pollution and causes people to have black, charcoal-like skin in the lower limbs. This is caused by [[arsenic]] pollution in water and food source.<ref>{{Cite journal|last=Tseng|first=Chin-Hsiao|date=2005-01-01|title=Blackfoot disease and arsenic: a never-ending story|journal=Journal of Environmental Science and Health, Part C|volume=23|issue=1|pages=55–74|doi=10.1081/GNC-200051860|issn=1059-0501|pmid=16291522|s2cid=24276539}}</ref> This is an example of how disease can affect human variation. Another disease that can affect human variation is syphilis, a sexual transmitted disease. [[Syphilis]] does not affect human variation until the middle stage of the disease. It then starts to grow rashes all over the body, affecting people's human variation.<ref>{{Cite web|url=https://www.cdc.gov/std/syphilis/stdfact-syphilis.htm|title=STD Facts - Syphilis|website=www.cdc.gov|access-date=2016-11-16}}</ref>