‘Family tree’ is a good analogy.  As a tree grows, limbs divide and sprout off one another, as progeny sprout from their parents.  The newest, most immature, green branches sit always at the highest or furthest point from the trunk.  They are the most delicate and most flexible.  They soak sun and wave and sway and dance and shake and shiver in high winds.  Their parent limbs are dry, hard, wooden and do not sway so easily.  As the tree grows outward and upward, the immature limbs become stiff and thick, and eventually become covered by their children, who block the sun and breeze.  Every branch, at some point in the tree’s life was limber and bendable, and fluttered in the sun and warm breeze until the twigs sprouting from them radiated in all directions and left them fixed in the leafy shadows of the blotted sun.