Black Africans only have curly hair, but it's not long. African curly hair is about 256 microns long on average every day, while straight hair is about 396 microns long every day, which is really faster than curly hair.

However, when Africans have long hair, it is easy to turn into fluffy explosive heads, so many people don't like to have long hair, while those Africans who have long hair like oiling, knitting, twisting and various accessories to make their hair less "explosive".

Therefore, those black people with pigtails should have solid hair, not wigs. Besides, not all people with dark skin have curly hair. In fact, curly hair is a rare hairstyle in the world, and the skin of Native Americans is also very dark, but it is basically straight hair.

Cause analysis:

Africa is the continent with the richest skin color in the world, and the skin color of many people is similar to that of the indigenous people in America, which leads to a problem. After several generations, it is difficult to tell whether people with dark skin are of American or African descent.

So there is a very racist practice here, that is, American anthropologists at that time would insert a pencil into dark-skinned people's hair and then let dark-skinned people shake their hair a few times.

If the pencil does not fall, it will be judged as African-American, thus being discriminated at the highest level. If the pencil is dropped, it will be judged as an Indian and discriminated against in general.

Curly hair, like dark skin, is a "dominant" genetic feature, while straight hair is a "recessive", which was used by American anthropologists at that time to judge that the hair of African descendants would only become less and less curly and would not disappear completely.