Neanderthals inhabited Europe and the Near East until about 30,000 years ago. They disappeared after their successor, Cro-Magnon man, who was anatomically modern man migrated to Europe. Many theories have been put forth to explain what happened to the Neanderthals. One of these theories suggest that Neanderthals were a separate species apart from Cro-Magnon man and their birth rate was slower than that of Homo Sapiens; they were out competed and simply replaced within generations, by the more flexible and technologically more advanced Homo sapiens. Homo sapiens had a more complex and specialized tools made out of bone, ivory, and antler. With these innovations, Cro-Magnon did not have to work as hard as Neanderthals did in order to survive.
With a much more sophisticated technology, Neanderthals would have had to compete with modern humans for their meats. This led to starvation and a decrease in the overall Neanderthal population, which could have been the cause of extinction. In contrast with Cro-Magnon man who lived into their fifties, Neanderthals had a much shorter life span, barely surviving until the age of forty.
Another theory states that Neanderthals were not in fact a separate species, but interbred with Homo sapiens whose genes eventually became dominant at the eventual expense of the genes delivering into Neanderthal characteristics. This theory came from the fact that Cro-Magnon and Neanderthals inhabited the same regions of Europe for thousands for years.
The fate of the Neanderthals is never-ending until archaeologist finds evidence of their fate. However, they did have human characteristics. Neanderthals were compassionate enough to bury their dead, care for their injured and ill, develop complex tools, create some form of ritual behavior, and communicate in some ways. It is this aspect of humanity that was improved and carried on by their successors, Cro-Magnon man, who later dominated the world