Thanks for the great question!
The human body absorbs ultraviolet (UV) rays
from the sun through the skin to create Vitamin
D, which is crucial for preventing diseases.
However, too much absorption of UV results in
damage to the skin (sunburns and even skin
cancer). Variations in human skin color evolved to
optimize absorption of UV rays while
preventing damage to the skin. Skin is made darker
through the presence of a pigment called
melanin, which acts as a natural sunscreen.
The first human ancestors evolved in Africa
near the equator where sunlight is most direct
and so they had darker skin to protect against
overexposure. As humans migrated to more northern
latitudes, where sunlight is less direct,
lighter skin evolved to allow more absorption
of sunlight. So why, as your question
rightly points out, do the Inuit people of the
Arctic Circle, where the sunlight is the least
direct, retain skin darker than other ethnic
groups that live in the north?
The Inuit people are masters of their harsh
Arctic environment, creating technologies like
canoes and harpoons to hunt marine animals for
food. It turns out that the Inuit were very
successful at hunting animals like fatty fish that
were rich in Vitamin D. Thus, the Inuit were
less reliant on sunlight to produce this
vitamin as they could get it from their diet.
For this reason, natural selection did not favor
those individuals that happened to have lighter
skin tones among the Inuit, and darker skin tones
were able to persist among these populations.
Thanks again for the great question,
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