It is commonly known that, around 30,000 to 25,000 years ago, Neanderthals disappeared from the face of the Earth. It is thought that this event has something to do with humans arriving in Europe. However the precise causes are unknown. One theory is that humans hunted them to extinction. The fact that Neanderthals were bigger, stronger, more resistant to injury, had better stone tools and had grown accustomed to the ice age make this unlikely.
A more plausible theory is that humans just formed such large colonies, that Neanderthals just could not find enough living space and resources to maintain their species. This effect combined with a possibility of a lack of social cohesion in Neanderthal family groups could have led to their eventual demise. A team of archaeologists from Cambridge University made a series of studies of archaeological artifacts from various sites around the Dordogne region of France dating to three different archaeological time periods: Mousterian, Chatelperronian and Aurignacian.
These are all sequential and cover a period of 45,000 to 35,000 years ago. In this time we see that that the ratio of human to Neanderthal populations rose to heights of 9:1. We also see that population densities more than doubled and that humans had family group territories of up to 600 square metres while those of Neanderthals dwindled to less than 200. The maps below show the area of study and the size of the dots the population size.
We can see here that the size and number of human populations in the Dordogne show that in less than 7000 years, Neanderthals in Europe were reduced to stunted and isolated family groups, while humans would have been a common sight in prehistoric Europe. While these results do not explain the disappearance of Neanderthals, they do provide strong evidence for the population and social growth theory