French naturalist, explorer, and physician. Joseph de Jussieu was born in Lyons in 1704, the younger brother of the botanists Antoine and Bernard de Jussieu. During his education in Paris he was undecided whether to become a physician or an engineer, but on the advice of his brothers he eventually completed his medical studies and qualified in 1734. The following year he accepted a position as naturalist and physician on a scientific expedition sent by the French Academy of Sciences to equatorial Peru to measure an arc of meridian. The mission, which included the astronomers Godin, Bougher, and La Condamine, left La Rochelle in May 1735 and arrived in Peru in April 1736, after stopovers in Martinique, Saint-Domingue (Haiti), and Panama during which Jussieu commenced his collections and observations. In 1739 Jussieu made a visit to Loja in the Andes to study stands of cinchona discovered by La Condamine on his way from Quito to Lima.

When the expedition disbanded after completing its geodesic work in 1743, Jussieu remained in Peru, penniless and ill, forced to earn a living and save for his return passage to France. He would live in the region for another 27 years, supporting himself mainly by the practice of medicine, and between 1747 and 1750, carry out further extended explorations. By 1745, despite repeated bouts of fever, he had saved enough money to return home. In the meantime, however, his skills and devotion as a physician had become so well known that when a smallpox epidemic broke out in Quito he was forbidden to leave the city by formal order of the royal court. As time passed, he found himself increasingly torn between wanting to return home and the desire to explore unknown regions.

When he was finally able to leave the province of Quito in 1747, he went to Lima, where Godin had been living as first cosmographer of his Catholic majesty, and travelled with him to La Paz, at the request of the French Minister of the Navy and of the Colonies, Count Maurepas. After crossing the Great Cordillera, the two explorers navigated the Rio Urubamba as far Lake Titicaca, where Jussieu assembled a collection of aquatic birds. At the end of their journey, Jussieu continued alone to Yungas to study the cultivation of coca, and from there travelled northeast to the Majos region. He then recrossed the Andes and visited Santa Cruz de la Sierra, Oruro, and Chuquisaca before arriving in Potosí in July 1749 and settling there for four years.

He returned to Lima in 1755, exhausted and despondent. His family pleaded with him to return to France, but for many years he lacked the means or the will to leave. He finally returned to Paris in July 1771, after an absence of 36 years, his health broken and his mind beginning to cloud. His brother Bernard and nephew Antoine-Laurent cared for him in the family residence on rue des Bernardins. The botanical results of his explorations were large but he published nothing. Most of his collections were lost in transit and his manuscripts were destroyed in Lima after the death of the person to whom they were entrusted. Jussieu survived in a state of despondency for another eight years, never leaving the house. Although elected to the Academy in 1742, he attended not a single session.

Sources:
G. Dilleman, 1994, "Jussieu, Joseph de", in M. Prevost, R. d'Amat, H. Thibout de Morembert, and J.P. Lobies, Dictionnaire de Biographie Françe, 18: 1049-1050
Y. Laissieu, 1973, "Jussieu, Joseph de (1704-1779)", in C.C. Gillispie (ed), Dictionary of Scientific Biography, VII: 200-201.