Humans produce melanin in 3 forms: neuromelanin (B), eumelanin (both brown-black) (C), and pheomelanin
(golden yellow -red) (D).
That analysis not only reported one of the first demonstrations of pheomelanin
(the brown version of melanin) in non-vertebrates, but it also found that the grasshoppers kept on brown soil were rich in pheomelanin
, while the grasshoppers kept on gray stones were rich in eumelanin (the black version of melanin) (see Galvan et al.
In an attempt to unearth the factors favouring the evolution of pheomelanin
in spite of its costs, Ismael Galvan and Anders P.
They specifically excluded women with chemical hair treatment and utilised spectrophotometric hair analysis to confirm the pheomelanin
An easy-to-run method for routine analysis of eumelanin and pheomelanin
in pigmented tissues.
Skin contains two kinds of pigments, or melanins: pheomelanin
, which is reddish or yellow, and eumelanin, which is dark and brownish.
In a large number of mammalian species, the coat color diversity is mainly determined by the relative amount of the two basic melanins, eumelanin (black/ brown) and pheomelanin
(yellow/red), which are genetically controlled by the extension (E) and agouti (A) loci, respectively .
Certain defective MC1R variants are associated with a phenotype that shows red hair, fair skin, and predominance of nonphotoprotective pheomelanin
That tiny difference prevents the tiger from making the reddish and yellow pheomelanin
pigments, but does not affect the production of the black pigment eumelanin.
Light-skinned redheads with freckles and an inability to tan have trouble producing the black-grown pigment eumelanin, which absorbs harmful UV rays - instead producing the red-yellow pigment pheomelanin
which provides a weak UV shield.
Eumelanin is brown to black while pheomelanin
is yellow to red.
Individuals with red hair have a predominance of pheomelanin
in hair and skin and/or a reduced ability to produce eumelanin, which may explain why they fail to tan and suffer from increased cutaneous UV sensitivity and why UV irradiation is more dangerous for them.