WaPo on the exhibit "Revealing the African Presence in Renaissance Europe":

The exhibition of painting, sculpture, maps and prints is focused on 73 potent rather than visually sumptuous objects. If not always a feast for the eyes, the show is a compact and dense lesson in how race was conceived between the late 1400s and the early 1600s. It was a complicated period. In the 15th century, slaves were overwhelmingly “white,” brought from lands to the East, including Central Asia and Russia. Africans circulated and lived in Europe as emissaries and ambassadors, came for educational opportunities, participated in the dissemination of Catholicism, and occasionally rose to high rank in European courts. One of the Medici dukes of Florence was probably the son of a slave or servant of African descent, and former slaves achieved renown as playwrights, scholars and artists. But the same period also brought the codification of racism in the New World, the rigid association of dark skin with newer, crueler forms of slavery, and the invention and spread of vicious religious justifications for racism and enslavement. Shakespeare’s “Othello,” written near the end of the period covered by this exhibition, gives one a good sense of the contradictions and complexities of African life in a Renaissance context.
Why is this exhibit important? The core reason:
[T]he process is worth the effort, as the fascinating story of a painting by Jacopo da Pontormo demonstrates. The image includes a dignified woman of indeterminate age directly facing the viewer, and a small girl with tightly curled hair staring out of the painting to the right. In 1902, when the painting was acquired by Henry Walters, there was no little girl, just the woman, who was identified as a poet. Subsequent X-ray analysis revealed the girl, who had probably been painted out to make the image more attractive to collectors. Conservation returned her to view, and scholarship in the 1990s identified the girl as the daughter of the presumably mixed-race Alessandro de’ Medici, whose dark skin and tightly curled hair can be seen nearby in a small painting by Bronzino.
Much of the history we have today about early black African/white European encounters is a lot like this painting at the beginning of the previous century. A good part of what actually happened has been "painted out."