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The genetic modifications 'instructed' the same microbes that were growing the material to also produce the dark black pigment, eumelanin.

In work published in 2016, he and his colleagues looked carefully at the different trace metals in pigments from modern feathers and found that whereas eumelanin contains copper, pheomelanin contains sulfur and zinc.

A decade ago, scientists used high-energy synchrotron x-rays to identify the key chemical signatures of a pigment called eumelanin, which colors skin, hair, and other tissues black, brown, and gray.

Mantled howler monkeys typically have a type of melanin—the pigment that colors hair and skin cells—called eumelanin that is black, gray, or dark brown.

The cells produced more eumelanin, the pigment responsible for black and brown skin, hair, and eyes.