The line that is traced

Every human being has the same tree. Which line you trace through it is a choice, and cultures made different ones — most of the world followed the father's name, land and lineage; a few followed the mother's.

Jewish law took the second road: the child's status follows the mother (Mishnah Kiddushin 3:12; Talmud Kiddushin 68b). The reasons debated by historians are unglamorous and mostly legal. What is remarkable is only this: of all the possible threads through the tree, the matrilineal one turns out to be the thread that a piece of the body actually takes. The law and the mitochondria draw the same line — for entirely unrelated reasons, seventeen centuries apart. The room lets you flip between the two authorities and watch the drawing not change. Turn on the other line and the tree changes shape completely: a different set of ancestors lights up, equally real, equally yours.