Jake - I am not a scientist and the subject about Neaderthaals and others have been discussed by many before and have been rejected as well. For me the only one thing is enough that all those pictures you see of cavemen are the creation of people depending upon assumptions. Then even if they were living in caves then no one can say that they were not human but apes as in few parts of the worlds people might still be living in caves or cave like places.
Islam believes that God created human and he gave them different shapes during all of the process. And same way God created other creatures including apes and certain people were changed into apes as punishment too.
But nowhere Islam believes that Apes were changed into human.
Any way to answer your question I will post a link where someone else has taken the pain and gathered some information.
http://answers.yahoo....20101218122651AAGOZNn