Hand waving: the adult brain is the output of running a program stored in DNA for twenty years on a runtime (the physical universe) we can barley understand. To produce a brain from the data stored in DNA, we would need to simulate the runtime environment. To do that without simulating the whole universe, we would need to work out which subset of the universe to simulate. We are far away from knowing what shape that subset takes, let alone what the minimal number of bytes required to simulate it is.
