>Now, in practical terms, this means that, given a MZ twin who died recently of natural causes, we could obtain an estimate for ourselves,
Uh... am I misreading your comment, or are you suggesting that when your identical twin dies of non-accidental death, you can be pretty sure you're about to croak in the next wee days or weeks yourself? Very difficult to engineer that alarm bell (you either have a twin, or not), and too damned late to matter.
With a correlation of ~0.5 the window will be much wider than weeks or months, and it's more like, "If your MZ twin died of completely natural causes at 70, it is unlikely that you will live to 120."
Uh... am I misreading your comment, or are you suggesting that when your identical twin dies of non-accidental death, you can be pretty sure you're about to croak in the next wee days or weeks yourself? Very difficult to engineer that alarm bell (you either have a twin, or not), and too damned late to matter.