For most people in the past, we have no footprints, bits of writing, etc. A crude back-of-envelope calculation suggests that maybe it takes ~ 10^15 bits to describe one person’s brain; I wouldn’t be surprised to find that wrong by a couple of orders of magnitude, but in any case it’s rather a lot. Anyone who’s (1) in the not-very-recent past and (2) not exceptional in the traces they leave behind has left only very subtle such traces—which will be tied up in computationally intractable ways with everyone else’s very subtle traces, and with all kinds of extraneous cruft. I’ve no idea what might turn out to be possible in principle, and saying “we’ll never have the technology to do X” doesn’t have a great track record of success … but I wouldn’t hold out much hope of being able to retrieve enough information to reconstruct past people even with future-lightcone-scanning technologies, never mind without.
For most people in the past, we have no footprints, bits of writing, etc. A crude back-of-envelope calculation suggests that maybe it takes ~ 10^15 bits to describe one person’s brain; I wouldn’t be surprised to find that wrong by a couple of orders of magnitude, but in any case it’s rather a lot. Anyone who’s (1) in the not-very-recent past and (2) not exceptional in the traces they leave behind has left only very subtle such traces—which will be tied up in computationally intractable ways with everyone else’s very subtle traces, and with all kinds of extraneous cruft. I’ve no idea what might turn out to be possible in principle, and saying “we’ll never have the technology to do X” doesn’t have a great track record of success … but I wouldn’t hold out much hope of being able to retrieve enough information to reconstruct past people even with future-lightcone-scanning technologies, never mind without.