His father, Édouard Lartet was a prominent geologist and prehistorian who played a key role in the 1860s and 1870s in finding evidence that humans had lived during the Quaternary period and Louis continued his father's researches into human prehistory.
In 1868, Lartet was asked to conduct excavations in a rock shelter near the French village of Les Eyzies after workmen stumbled upon extinct animal bones, flint tools, and human skulls.
Lartet discovered the partial skeletons of four prehistoric adults and one infant along with perforated shells used as ornaments, an object made from ivory, and worked reindeer antler.
These Cro-magnon humans were soon identified as a new prehistoric human race distinct from the Neanderthal man fossils discovered in Germany in 1856.
Lartet began teaching geology at the University of Toulouse in 1873 and in 1879 he became a tenured professor of geology at the university.