At least sometimes parts aren't prior to wholes

1. Efficient causes are explanatorily prior to their effects.

2. Circularity of explanatory priority is impossible.

3. I am the efficient cause of my teeth—I grew them!

4. Therefore, my teeth are not explanatorily prior to me. (1–3)

5. My teeth are parts of me.

6. Therefore, at least some parts are not explanatorily prior to the wholes. (4, 5)