<p style="font-weight:400;">Here's a theory I came up with. It's kinda contrived lol but I was thinking it's possible.</p>
<p style="font-weight:400;">Moon.....................................Ocean</p>
<p style="font-weight:400;">Tui = Push..............................La = Pull</p>
<p style="font-weight:400;">Female...................................Male</p>
<p style="font-weight:400;">Good......................................Evil</p>
<p style="font-weight:400;">Life.........................................Death</p>
<p style="font-weight:400;">Yin.........................................Yang</p>
<p style="font-weight:400;">So my theory for bending is that the Lion Turtles granted the powers to the humans venturing into the Spirit Wilds but they were not the original benders (think the actual ART form) themselves. Once the people were granted the power to waterbend, then they actually learned from Koi fish to waterbend that were plentiful at that time. So learning bending is the art of which the animals/spirits are based on, not the actual bestowers of the powers. Over time, waterbending Koi had died out save for Tui & La who have actually given up living in the Spirit World and switched their identities when they moved to our world (which is why Yin is white, female and reps the moon when Yang is black, male and reps the ocean) so as to make it difficult to tell which is which. So actually it is: Moon = La = pull = Male = Life = Good = Yang AND Ocean = Tui = push = Female = Evil = Death = Yin originally in the Spirit World. Over the years, the water tribe hunted the waterbending Koi to extinction and through oral tradition, they came to believe they learned how to waterbend from the moon (and not the moon AND ocean spirits which were waterbending Koi; also explains why waterbenders traditionally didn't move their feet much when waterbending, they were mimicking a fish :D). </p>
<p style="font-weight:400;">Fire (Sun/Light)........................................Heat (Magma/Inner Core of Earth i.e. the "heart")</p>
<p style="font-weight:400;">Ran = Ignite/Light/Spark........Shaw/Shao = burn/warm/fuel</p>
<p style="font-weight:400;">Out..........................................In</p>
<p style="font-weight:400;">Male........................................Female</p>
<p style="font-weight:400;">Expression.............................Restraint</p>
<p style="font-weight:400;">Yang...........................................Yin</p>
<p style="font-weight:400;">Ran and Shaw signify the fire/light of the world and the heat/warmth of life respectively. Together they create combustion i.e. a flame. They, unlike the Koi, did not switch their identities when migrating into our world, hence their correct genders and yin/yang representations. I personally believe firebenders learned how to firebend from dragons, however, if the same phenomenon happened in the Fire Nation (i.e. oral tradition being passed down and the last dragons dying out much earlier), they would have said that the original firebender was the Sun and that the first firebenders watched how it rose and set bringing light and warmth to the world.</p>
<p style="font-weight:400;">Ran and La together keep balance between the sun and the moon and by extension between light and dark. Without Ran, La's darkness will overrun the world causing sorrow and apathy; without La, Ran's ambition and desire will cause pride and imperialism in the world (as what happened with the Fire Nation).</p>
<p style="font-weight:400;">Shaw and Tui together keep balance between the heat and the cold and by extension, between life and death. Together, they keep life in balance, without Tui, Shaw's fuel will overpopulate and explode; without Shaw, Tui's tranquility will stagnate and cause life to die off. This is also why Tui needs the pull of La to pull her tides and keep her moving.</p>
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<p style="font-weight:400;">All four spirits are cross-interconnected quadrilaterally. :)))</p>