Spanish physician. Born in la Puebla de Montalbán, near Toledo, Hernandez studied at the School of Medicine in the University Alcalá de Henares between 1530 and 1536. After graduating he began to practice medicine whilst undertaking post graduate studies in Torrijos and Seville. In 1555 he began his botanical fieldwork and at this time married Juana Díaz de Paniagua. From the late 1550s until the 1560s he studied and worked in the hospitals and monastery of Guadalupe (which was a hub for anatomical studies).
Due to his extremely good education in medicine, the classical languages and philosophy, he was appointed personal physician to King Philip II. He worked in this role for three years. However, at this time of inquisition from the Catholic Church, Hernandez's Jewish routes and philosophical views put the King in an awkward position. Wishing to utilise Hernandez's medicinal expertise without being directly coupled with him, Philip II ordered Hernandez to undertake the first official systematic scientific exploration of the Viceroyalty of New Spain. Hernandez was to study all aspects of the natural and cultural history of New Spain (which included present day Mexico, some of the Southern United States, Central America, the Caribbean and the Philippians) and to travel down to Peru.
In 1570 he left with his son Juan and together they collected on the Canary Islands, Haiti, Hispaniola and Cuba on their way to Veracruz. It was also requested by the King that Hernandez should assess the state of the local physicians of the Viceroyalty, but the inquisition made this very difficult for him so he focused all his attention on collecting plants and learning about their uses in the indigenous cultures. He travelled almost immediately to Mexico City, where he would remain based for the entirety of his seven years in the New World, but it is unclear exactly where he travelled. He certainly made excursions throughout the Valley of Mexico, collecting and observing the climates in which certain species were able to grow, but he never even reached Guatemala, let alone Peru as the original expedition was intended.
He learnt to speak Nahuatl and a great deal of his knowledge came from questioning the native people on their uses of plants. Unlike other settlers who only saw the local people as a threat to their health, Hernandez used them to increase western knowledge of medicinal substances. In a Yellow Fever epidemic in 1576 he performed many autopsies in the Hospital Real de San José de los Naturales. When he returned in 1577 Hernandez had identified and described over 3000 plant species entirely unknown to western science. So baffling were his findings that it would be years before European taxonomists could integrate them into their knowledge of plant relationships. Hernandez spent the last 10 years of his life as physician to the Kings son (later to be Philip III). His findings were written up in 6 folio volumes, in Latin, entitled The Natural History of New Spain but he died before they were published. They were housed in El Escorial where generations of scientist consulted them, until they were unfortunately destroyed in a fire in 1671. Luckily they had been copied and cited so frequently by this time that his work remains popular and informative to this day.