I have a question about the use of the definite article in English. Below are two sentences from a google search result:

"My work draws on concepts and methods from a range of approaches in the human sciences, including anthropology, actor-network theory, psychoanalysis, narratology and cultural geography."

"These papers were written by researchers from around the world; the topics covered a variety of disciplines and theoretical approaches in human sciences: psychology, anthropology, sociology, information and media sciences; computer sciences and engineering"

Now, what is the reason that "the" is used before "human sciences"in the first sentence but not in the second? Does it create a difference, even if subtle, in meaning?

Also, even regarding the phrase "the use of the definite article" I have some problems. I have encountered cases where the phrase appears without the definite article: "the use of definite article". So, is it optional in this case to use the definite article "the"?
Thank you very much,