Theodosia Ann Barker was born on 29 March 1819, at
Thetford, England. She was the daughter of Edmund H. Barker, a scholar, and the editor and author of several literary works. She had an older sister. Discovering in early life a love for books and a capacity for acquiring knowledge, the parents of Dean afforded her every opportunity for study, under their tutelage. From the age of thirteen to sixteen, she attended the boarding school in Bracondale,
Norwich, kept by the nieces of
Henry Kirke White. At the age of seventeen, after completing her studies, including learning several European languages, she started studying the Chinese language under the instruction of the Chinese professor in the
University of London. The following year, she was appointed to sail for China, under the patronage of the
Society for Promotion of Female Education in the East. For a few months before her departure, Dean prepared for her voyage and spent time with home friends. On 9 August 1837, Dean left
Hackney and proceeded via steamer to
Gravesend, from where she immediately embarked on board the ship
Hashemy. She enjoyed the companionship of fellow-voyagers from England to Batavia, but on to China, she was a lone passenger. On reaching Macau, she became a member in the family of Rev.
Karl Gützlaff, and continued her study of the Chinese language. In March 1838, at Macau, she married Rev. William Dean of the
American Baptist Foreign Mission Society. Together, they proceeded to
Bangkok,
Siam, where she soon established a Chinese school and provided instruction for the next five years. Through her teaching and study, Dean became well-versed in speaking and reading the Chinese language. The health of her husband failing at Bangkok, she sailed with him for China in 1841, where they arrived in May 1842 at Macao, at which place their daughter was born. In the latter part of October 1842, she took up her residence at
British Hong Kong. Here, she and her husband, who was affiliated with the American Baptist Mission, organized a new Chinese church, and planted a new station for the class of Chinese speaking the
Tie Chiú dialect. ==Death and legacy==