There is good evidence that human skin color is an adaptation to
the amount of sun exposure regularly experienced by populations in
different environments. UV radiation from the sun has both negative
and positive effects. UV radiation breaks down
(1) in the body, which is detrimental
to (2) in
men because it can negatively impact (3)
production and is detrimental to
(4) in women because it can
cause (5)
defects in developing fetuses. But UV radiation
is also crucial for (6)
synthesis, which is beneficial for
(7) in both men and women
because (8)
prevents metabolic diseases such as
(9) .
Dark skin has more (10)
than light skin, which causes the skin to be more
resistant to UV radiation. In (11)
environments, no one has trouble getting
enough (12) to
synthesize (13) , but
people with darker skin are more resistant to
(14) degradation (breakdown), so
they have more (15)
than people with light skin. They pass the trait of
dark skin on to their offspring, resulting in populations
characterized by dark skin. In (16)
environments, no one has trouble with
(17) breakdown because
there is not much (18)
, but people with light skin better able to
synthesize (19)
than people with dark skin, and therefore have fewer
metabolic diseases and more (20)
. They pass the trait of light skin on to their
offspring, resulting in populations characterized by light
skin.
choose from the following: reproductive success,
melanin, sunny, Vitamin D, less sunny, UV radiation, sperm, neural
tube, rickets, folate