Yes, curly hair is considered a dominant trait.
The curly hair of a person is determined by the gene of his/her parents instead of the external environment.
The curly hair gene is dominant while the straight hair gene is recessive. Therefore, if one of the parents has a curly hair gene, then it is more likely that the child will also have curly hair.
It is found that external factors such as climate conditions and geographical locations are responsible for the evolution of human hair and straight hair is its new trait.