Neanderthal
Neanderthals are an extinct species or subspecies of archaic humans who lived in Eurasia until about 40,000 years ago. While the "causes of Neanderthal disappearance about 40,000 years ago remain highly contested," demographic factors such as small population size, inbreeding, and random fluctuations are considered probable factors. Other scholars have proposed competitive replacement, assimilation into the modern human genome, great climatic change, disease, or a combination of these factors.