How did the concepts of left and right direction develop in the human mind? I hope this is the correct forum to ask; if not, please migrate to a better place.

How did humans came to agree on a distinction between the directions "right" and "left"? I could think of two alternative ways:


Biology: the right hand is usually stronger, so humans can agree that the direction of the stronger hand is "right" and the other direction is "left".
Astronomy: in the northern hemisphere, when people look to the direction of the rising sun (= east), they see it turning slightly to the right of them (= south). So they could agree that the direction the sun turns to is "right" and the other direction is "left".


Is there any evidence to one or the other or to another explanation?
There is a perspective called the "sociological imagination" that can be used to "frame," or interpret, perceptions. In part, this perspective involves an awareness toward the linkages between history and biography, between social structure and consciousness, and between "knowledge" and its socio-cultural contexts.

The words you question are simply tools or descriptive labels applied to some "sense" and useful for both individual and communal understanding of space-time.  There is a class of words (called "closed" class words) -- called so because, unlike nouns and verbs, it is tremendously difficult to invent new words (icons or symbols) for the associated concepts.  These words fall into a class of words that have their foundation in protolanguage -- with associated, generally-accepted, emerging concepts from early hunting and gathering societies 100,000BC-80,000BC.  At this early stage, knowledge transfer (education) was through socialization of the young (largely an informal process where children learned both through their play and through observing and imitating their elders).

Specifically to your question, some close class words indicate relative direction (to, from, through, left, right, up, down) in the manner of vectors.  Other words such as above, below, in, on, at, next to, and by serve to orient relative to other objects.

Suppose one had to explain the meaning of the words “left” and “right” to someone who had never heard those words before. Further suppose, that you had to explain such in a purely verbal manner -- without drawing pictures or pointing at things or otherwise making gestures.  One would perhaps start by appealing to a shared experience, communal concept, or draw upon mathematics (geometry).  But what if one were constrained to make no assumptions about where the person is coming from or how much geography he or she knows? You then might hope that they knew something about the stars or the sky.  One could begin with up and down and move on to the motions of objects in the sky.

Another way the concept of "left" and "right" could have emerged to common understanding is through anatomy (human or otherwise).  Socializing methods of butchering flesh, combat training, and burial rites all would include relative orientation, placement, and direction.

The cognitive origin of the notions of "left" and "right" emerge from common experience and/or how experience relates to tangible objects or phenomenon.

This rabbit hole goes a lot deeper; however, for the sake of being cogent and succinct, I am observing some self-imposed boundaries.  There are egocentric coordinate acculturation conventions and spatiality (geo-centric, stellar-centric, (sub)atomic-centric) traditions that can shake things up a bit but I believe such begin to tangent off point.



References:

Calvin, W. (2004). A brief history of the mind: From apes to intellect and beyond. New York: Oxford University Press.
The New Ambidextrous Universe: Symmetry and Asymmetry from Mirror Reflections to Superstrings: Third Revised Edition. By Martin Gardner​. 2005.
The Handedness of the Universe. Roger A. Hegstrom and Dilip K. Kondepudi in Scientific American, Vol. 262, pages 108-115; January 1990.
Alien Pizza, Anyone? On other worlds, biochemistry could have taken a different turn. Davide Castelvecchi in Science News, Vol. 172, No. 7, pages 107-; August 18, 2007
THEORIES. (n.d.). Retrieved March 3, 2015, from  http://www.trinity.edu/mkearl/theory.html#imag