man

I was asked what the difference between human, human being, person, human race, mankind, and man was by my Swiss friend. And being such a loaded question, I had to mull over it for about a day. The following morning, I had my morning coffee and built up the boldness to piece together my scattered thoughts. The following is not meant to be a complete analysis; I did not look into the history and etymology of each word. It is just a primer to a possible research project at a later date.

1) Human(s) was originally a French word which I suppose came into the English Language after a word had already existed for the concept of man and human. French words supplied English with sophisticated nuances and abstract ideas, e.g. beef vs.cow meat, mansion vs. house. Thus, the word human most likely took on this subtly intricate gradient of meaning. Today, the word is used when talking about it as a physical body sans the spirit and emotions, i.e. in the sciences. We do not say the person body or man body but the human body. We are not the person or man race but the human race. It is often used in conjunction with words such as evolution, species and cloning. 

2) Although the word 'human being' and 'human' do share several gradients of meaning, there also seems to be a stark difference in the emotional response of the speaker/listener. Many times, when the question of life and spirituality arises, human being is the favored word.

    What are human beings that you are mindful of them, mortals that you care for them? 
     - Psalms 8:4

     You wonder why your life is screaming, Wonder why we're human beings. 
     - Van Halen

It also seems to be used when contrasting man with a god or an idea of some sort. We step away from being a human for a second and critique the race and find meaning in it.

3) The word person is most often used in daily speech. It is who we see and interact with everyday. "I like that person" or "I saw that person yesterday" are common things we say. This word is from a latin cognate and took on this stoic meaning. (In italian person is 'la persona.') The plural form of person, people, can interestingly be used as a verb as in "the island of Australia was peopled by deported criminals." The word likely started as a noun and was verbified and verbification regularly happens with words that are commonly used. What would be interesting to see is how people came to mean many persons.

4) The human race is normally used to contrast it with other races other than humans. It is frequently used in movies and video games with aliens or monsters. In mythology, there is the elven race, the dwarven race, and the orc race. The human race also refers to all of man as a whole. Statements must be satirical, a general truth, or a critique. Mark Twain says, "The human race is a race of cowards; and I am not only marching in that procession but carrying a banner."

5) Mankind seems to be used a lot in the telling of stories and histories. It is a word of extremes: triumph, valor, and courage, failure, danger, and weakness. The famous quote "That's one small step for a man, one giant leap for mankind" succinctly demonstrates that. In contrast, Albert Einstein once said, "We shall require a substantially new manner of thinking if mankind is to survive." 

6) In its simplest form, man is the male species. It is also the idea that encompasses man and woman. In its more complex form, it includes not all but many of the meanings of the words above. This makes it a very elaborate word and tricky for learners of English. It is most likely the oldest of all the words discussed to have come into the English Language. We see cognates in other Germanic Languages that point to this antiquity. (e.g. der Mann in modern German) 

My speculation is that all the previous words came into the language at different points in time and assimilated certain meanings of the word man. Sometimes the dual usage was unnecessary and one was made obsolete. Other times, the two coexisted peacefully. This process is the reason why it is difficult to concretely narrow down the meaning of each word. I have tried to draw attention to distinct meanings each word contains but am not proposing that they cannot intermingle. Many in fact can be interchanged without significant loss in meaning and nuance.