I've researched my family history, in some cases back to the 1500s and earlier, and am more than reasonably certain not a single person on my family tree was confused as to his or her sex. Otherwise, of course, they wouldn't have been on my family tree.
The men impregnated the women, the women bore children, both male and female. Their children grew up, married people of the opposite sex, and continued the process until - voilà! - little mountaineer came along, mewling and puking in the nurse's arms.