Many varieties of orange exist today. However, every variety
traces its roots to the man-made hybrid created by crossing the
pomelo with the mandarin. The pomelo is almost as bitter as the
grapefruit, while the mandarin is sweet. The mandarin has an
orange color, and some people misidentify it as a variety of the
orange, but the mandarin is an ancestor of the orange.
The history of the orange is unclear, but it is believed to have
first appeared in southern China. Humans have selectively bred
oranges to create many varieties, making it easy to confuse the
orange with other citrus fruits. A fruit needs to have evolved
from the pomelo and mandarin to be considered an orange.
A tangerine is not
considered an orange, because it evolved from the mandarin, but
not the pomelo.