Skin color is the principle trait used, although hair, shape of head, eye fold, body build, etc are also used.
(Skin color; is; the principle trait used) (the principle trait; used; ) (hair, shape of head, eye fold, body build, etc; are also used; )
Skin color the principle trait hair, shape of head, eye fold, body build, etc
is used are also used
the principle trait used