Thomas Brodie (Genesis As Dialogue) argues that "Genesis consists of twenty-six diptychs. Building on older insights that several Genesis texts occur in pairs and that Genesis is somehow binary or dialogical, this study makes a basic observation: The entire book is composed of diptychs—accounts which, like some paintings, consist of two parts or panels." He gives several examples: "There are . . . two panels of creation (1:1–2:24), two of primordial sin (2:25–4:16), two genealogies (4:17–chap. 5), two parts to the flood story (6:1–9:1:17), two complementary histories about Noah's sons (9: 18–chap. 10), and so on—to a total of twenty-six diptychs (six in chaps. 1–11, seven in the Abraham story, six in the initial Jacob story, and seven in the Joseph story). Genesis then falls into fifty-two panels—a refinement of the medieval division into fifty chapters" (xi-xii). Twenty-six, you say? As in the gematria of YHWH? After the double creation account, Brodie finds a double account of the fall - the forbidden fruit in the garden (2:25-3) and Cain's murder of Abel (4:1-16). The two accounts are linked in multiple ways. They tell similar stories, but along a different axis: "Rather as the creation diptych (Gen. 1: 1–2:24) was representative of the two basic types of creation narratives, so the crime-and-punishment diptych also is broadly representative. The first crime is primarily vertical, against God; the second is more horizontal, against another human being. Furthermore, these two crimes involve two of the most basic pairings in life: man-woman; and brother-brother. By portraying two basic couples and two basic kinds of crime or sin, the diptych as a whole is typical or representative" (143). Here is a modified version of Brodie's chart of the parallels between the episodes (144):

The setting
They. . .the man and his wife. . .	The man knew. . .his wife
The serpent. . .of the field. . .	Sin crouching. . . into the field.
Fruit forbidden by God.	Fruit not regarded by God.
Problem: relation to God.	Problem: relation, through God, to Abel.
The drama on the face: the eyes' delight, desire.	The drama on the face: distress, face fallen.
Crime and punishment
After eating: they knew. . .	After killing: Where is Abel. . . ?
They heard the voice. . .	The voice. . .is crying to me
I hid.	I must hide/be concealed.
Avoiding responsibility: : It was the woman. . .the serpent.	Avoiding responsibility Am I my brother's keeper?
Because you have done this, cursed are you. . . cursed is the ground because of you.	What have you done? Now you are cursed from the ground.
The aftermath
God's protective action: Clothes them.	God's protective action: Puts a sign on Cain.
God cast them out of Eden.	Cain went out from God.
Cherubim placed east of. . . Eden.	Cain dwelt east of Eden.

Beyond this, the double fall is echoed again later on in the post-diluvian account of Noah's sons: "The two sin accounts (2:25–4:16, including Cain) are mirrored obscurely in the stories of Noah's sons (including Canaan, 9:18–chap. 10). In particular, the drama of the tree, nakedness, and the eyes (2:24–chap. 3), is partly reversed in the drama involving another strange tree (the vine) and the turning away of the eyes from nakedness (9:18–29)" (17).