The term Neanderthalensis refers to the species HOMO neanderthalensis, which is an extinct species of human that lived in Eurasia during the Middle Paleolithic period. It is believed that they were the first humans to use tools and fire, and they are closely related to modern humans. Neanderthals were also known for their large brains and robust bodies. They became extinct around 40, 000 years ago, likely due to competition with modern humans.