It is the same in Humanities (History, Theology, Byzantine Studies).

Well, as others have stated before, the authors would traditionally appear in alphabetical order, however, in some cases, you may want to start with the one who is the most prominent one, or, in different words, if someone writes 5 out of 7 chapters in such manuscript, and, for example, others have contributed "only" with 2 remaining chapters, you could, technically, call them co-authors, and, therefore, you can put the author of predominant 5 chapters on the first place.

Not in my field (social work, psychiatry) --the senior author is the last author is usually the most recognized in the field.