Unit studies and humanities courses can be the same thing. Unit studies is often associated with subjects not defined as humanities, but a teacher can use a unit study approach to any humanities class. First we have to get a general definition of humanities courses and unit studies.
Unit studies refers to a method in teaching which incorporates every aspect of a subject. For example, if you were to teach a class about volcanoes, you would teach where they are, how they form, their effects on people, etc in such a way that you are teaching geography, geology, spelling, social studies and many other subjects simply through volcanoes. Once the volcano topic has been fully covered the teacher will move on to another topic related to volcanoes, and repeat the process to cover whatever topis they need to. This is in contrast to the more common method of simply teaching the basic parts of a volcano and moving on to another, unrelated topic. It is thought that unit studies give a student more understanding of the subject and helps them to retain the knowledge longer. So as you can see a unit study is simply a way to teach a subject.
Humanities courses can be taught unit studies methods. A humanities course is any course that examines how humans interact with each other. Civics, political science, history, psychology and many others are often classified as humanities classes. Humanities and unit studies seem to be natural fits. It would be very easy to look at an area of the world (geography), discover how they structure their country and cities (urban development), and see if there are any ties to what the country is like politically (political science). With a class structure like this it seems much easier to teach an entire history of a particular country and have the students remember the course material. Most humanities classes incorporate many different topics, so why not go with a unit study approach?
So now you know that unit studies and humanities courses do not have to be different things. In fact, they can go very well together in helping students learn. For some reason many humanities courses are not taught as unit studies despite the fact that they are great fits. So if you are a teacher, perhaps you should consider teaching your humanities course as a unit study.