Ying and Yang.
Adam and Eve
"A Glyph , generally a circle but sometimes oblong with two parallel lines drawn through its center dividing it into three parts , is a common universal symbol." This glyph refers to the Creation of man.
A circle with one line, means "two in one"
In "Sacred Symbols of Mu" Chapter IV. The Creation. Col.J.Churchward.
Out of several Creation stories, that all tell of one that became two;
"Lao Tzu in "Tao te King", a Chinese book written about 600 B.C. just before the time of Confusius, we read; "Reason Tao made one. One became two. Two produced three. From these three all of mankind descended"