In what sense is the new resurrected body like the old, and in what sense is the new different from the old? Fr. Ronald Knox, a convert from Anglicanism and a translator of Sacred Scripture, offers this insight:
“Surely the fact that my body differs in respect of every grain of matter in it from the body I had seven years ago makes it easier, not harder, to understand the resurrection of the body? Because if my body is made up of different material particles and is nevertheless continuous with the seven-years-ago model, that means that continuity even of the body is something independent of mere matter. And if so, I do not see why God should not give me a Resurrection Body which is continuous with the body in which I write now, without having to search round for bits and pieces of the multitudinous matter which has, in my time, gone to the making of me.” — Fr. Ronald Knox, Off The Record, (London: Sheed & Ward, 1953), p. 171.
We might say the same about the Body of Christ in the Eucharist. Does the dogma of the Real Presence require us to believe that the molecules of the hosts are the same as the molecules of the body of Christ when He walked this earth? Certainly not. There are more molecules in all the hosts of the world, than would be included in one man’s body. So it is similar with our resurrected bodies. The molecules need not be the same. God does not gather together, at the Resurrection, all the molecules that were once of your body, and make a new body out of them. The new body is pattered after the old, just as the body of an adult is patterned after his body as a youth, and as a child. As a child, they say, ‘He has his mother’s eyes.’ And as an adult, they might say the same.