Lamarck built the first full theory of evolution and died in poverty
Jean-Baptiste Lamarck coined the word invertebrate, helped give biology its modern name, and in 1800 laid out one of the earliest coherent accounts of species changing over time. When he died blind in 1829, his family had to ask the Academy for money, and his remains ended up lost from a temporary lime pit.
Before any of that he was a soldier. The eleventh child of a poor aristocratic family in Picardy, he rode off to join the army in Germany after his father died in 1760. During the Seven Years' War his company was shelled down to 14 men with no officers left. Asked to take charge and pull back, the 17-year-old volunteer insisted they hold their post until relieved, and the colonel promoted him on the spot. His military career ended after a comrade playfully lifted him by the head, leaving him with inflamed neck glands.
Botany came next. Stationed in Monaco, he picked up a book on useful plants, and after leaving the army he studied French flora for a decade under Bernard de Jussieu. His three-volume Flore française of 1778 made his reputation, and Buffon helped him into the Academy of Sciences a year later. During the Revolution, in 1790, he renamed the Jardin du Roi the Jardin des Plantes to drop the link to the king. In 1793 the new natural history museum made him professor of insects and worms.
Studying fossil molluscs from the Paris Basin changed his mind about fixed species. The shells shifted over geological time in step with the environment, and he rejected extinction or migration as explanations. In an 1801 book he split spiders from insects and crustaceans into a class of their own. His 1809 Philosophie zoologique set out a ladder of rising complexity, plus a second force that fitted creatures to local conditions through use and disuse. The inheritance of acquired traits now called Lamarckism was actually an older idea and a small part of his scheme.
Not all his ideas held up. He attacked Lavoisier's chemistry, and argued that continents crept steadily westward as ocean currents eroded their eastern coasts. Georges Cuvier mocked his transformation theory and, after Lamarck's death, used a eulogy to belittle him. Scientists still debate whether modern epigenetics vindicates Lamarck in part.
Source: Jean-Baptiste Lamarck
