The advent of colonialism and world travel presented new obstacles for women. Travel on horseback (or on donkeys, or even camels) was often impossible to do sidesaddle because the animal had not been "broken" (trained) for sidesaddle riding. Riding costumes for women were introduced that used breeches or zouave trousers beneath long coats in some countries, while jodhpurs breeches used by men in India were adopted by women. These concessions were made so that women could ride astride a horse when necessary, but they were still exceptions to the rule of riding sidesaddle until after World War I. Travel writer Isabella Bird (1831–1904) was instrumental in challenging this taboo. At age 42, she travelled abroad on a doctor's recommendation. In Hawaii, she determined that seeing the islands riding sidesaddle was impractical, and switched to riding astride. She was an ambitious traveller, going to the American West, the Rocky Mountains, Japan, China, Baghdad, Tehran, and the Black Sea. Her written accounts sold briskly.