It isn't, there are plenty of journal articles about human evolution.
I thought humans were the top of the evolutionary chain and therefore that is where evolution should be taking place.
There's no such thing as "the top of the evolutionary chain" (this is based on an extremely distorted misconception of evolutionary biology), and thus such a non-existent place is hardly "where evolution should be taking place". As others have pointed out, for a variety of reasons human evolution would actually be slower than that of many other animals.
Mainly because evolutionary scientists don't have an explanation as to why the human race doesn't appear to be evolving.