Neanderthals first appeared in Europe and Western Asia about 350,000 years ago. They knew how to use fire, could make rudimentary tools and hunting weapons, and possessed a limited form of vocal communication. Shortly after the arrival of the ancestor of modern humans, CRO Magnons, the Neanderthals disappeared. The possible reasons for the demise of the Neanderthals have been the subject of intense scientific and anthropological debate ever since the skull of a Neanderthal child was discovered in Belgium in 1829.

One theory suggests that the new arrivals exterminated the previous occupants through violent confrontation. To back up this claim, exponents point to archaeological evidence showing that the weapons of CRO Magnons were more advanced than those of their adversaries. Critics, while accepting that this was the case and admitting some bones show injuries consistent with spear attacks, believe that the evidence is too scant to confirm such violent conflict was widespread.
Another possibility is that the Neanderthals died of diseases they contracted from being in close proximity to the newcomers. Their immune system would have put up little resistance to the pathogens and bacteria carried by CRO Magnons. Whilst this is a plausible explanation, most agree that with the disintegration over time of all available physical evidence, it remains a very speculative guess.

Perhaps the most convincing argument is based on the anatomical differences between the two species. CRO Magnons were much lighter and could run much faster and cover greater distances than the Neanderthals. Anatomical differences in the thorax and position of the vocal chords meant CRO Magnons were capable of quite complex verbal communication too. And finally, whilst the Neanderthals lived in small, isolated communities, CRO Magnons made contact and even traded with distant settlements thus establishing a support system between communities.