Limit Break Dancing
Anyone who's taken an illustration class knows that skin tone is one of the last things the artist considers when drawing people. Eyes, nose, and mouth features are far more important for conveying race, sex and gender, age, and attitude. Next is hair, followed by clothing and personal effects. Whether or not to add shading or tone to the skin (and how much of it to add) are usually the last things the artist will consider. And depending on the media being used (especially pen and ink), it is often omitted altogether. See the line art drawings that @Sacrosanct posted.More the point, it's not about literally capturing bronze skin in a b/w line art per se. "Tanned white person" isn't much more diverse than just "white person in general" if the physical features are the same (Caucasian). So it's less about capturing actual skin tone, and more about capturing defining and diverse physical features, which absolutely can be done in b/w line art (see my post above).
Shading in the skin is usually only necessary when the artist wishes to emphasize the skin tone, or to contrast it with other people in the frame. This was most notably done in a lot of the older woodcarving and ink illustrations that European explorers made of the indigenous people they met in Cuba, Hawaii, and the Americas. There were very specific (and sinister) reasons for wanting to emphasize the complexion of the peoples they met and the images they brought back to Europe.