Coming as a big surprise to many, evidence has been uncovered that shows that humans and neandertals interbred. This evidence shows that "about 1 percent to 4 percent of DNA in modern people from Europe and Asia was inherited from Neandertals." However, it is unsure how long this interbreeding may have lasted. A comparison of the genomes of neandertals to those of chimpanzees and humans showed that our species are not that far apart. Researcher could only find "78 proteins in which humans carry a different amino acid than is found in Neandertals and chimpanzees." The fact that humans and Neandertals could interbreed has raised the question "whether the two groups are different hominid species."
This discovery does not surprise me very much. New species often evolve as result of inter species breeding. It is a basic evolutionary process. However, this could make some people rather uncomfortable. We as humans tend to like to think of ourselves an elite somewhat "pure" species. Any thing that provides evidence to the contrary is kind of unnerving.