[2][3][4][5][6][7] Born in Marseille on 24 June 1767, the son of Jacques-Joseph Eyriès, a "lieutenant de frégates du roi" ('lieutenant of the king's frigates'), and Jeanne-Françoise Deluy (1748–1826).
Returning to Le Havre, he began working in the armaments trade, including commercial expeditions to various parts of the world, while taking care of a natural history museum there.
In 1794 he went to Paris to free his father, who had been detained as a suspect in the new Republic, moving there the following year to devote himself to his studies, where he attended lectures by Antoine Laurent de Jussieu and Georges Cuvier, and started collecting old travel books.
[2][4] He was given a mission in 1804–1805 by Charles Maurice de Talleyrand-Périgord and Napoleon to travel to Germany and rally the French emigrants there, chosen for his knowledge of the country and language and his discretion.
He used the opportunity to continue his collection, but turned down the title "conseiller d’État" ('councillor of the State') to keep his independence, allowing him to devote himself entirely to geography and botany, and return to Paris to settle.