I had some doubt about the usage of Human beings, Mankind, people, Humans, Humankind & Human being. I noticed that there are some questions about those words in 'ELL' community, but none of them brings all words on to the same page.
I went through a lot of articles and made the following short note for my self. I believe that I have manipulated above-mentioned words correctly. Please advise me if I have made any mistakes.
Human beings(/ Mankind/ People/ Humans) have always believed in god.
Humankind/ (Human being) has always believed in god.