On 2011-05-20, Joe Makowiec <[email protected]> wrote: > On 20 May 2011 in soc.genealogy.computing, Peter J. Seymour wrote: > >> This amused me. Toying with providing better resilience in report >> annotation at high generation numbers, I encountered this unhelpful >> piece of numerology: >> >> Generation 149: G146 Grand Parents List size 16 individuals (out >> of 356811923176489970264571492362373784095686656 possible) > > I didn't do the calculation out to check the low digits, but the order > of magnitude is correct. > >> As far as I know the number is correct. I would not be surprised if >> it is more than the total number of atoms in the universe. > > Actually, it's about the square root of the total number of atoms in > the universe, which is estimated at about 10^80. (The number above is > 3 * 10^44.) > > http://en.wikipedia.org/wiki/Observable_universe#Matter_content > >> Obviously, as you go back through a binary ancestral tree, the span >> doubles at each generation. At the same time, on travelling back in >> time the total world population size dimishes. The bottom line is a family tree is _not_ a tree; it's a directed acyclic graph. (Some have called it a forest, but I don't remember the precise definition of a forest.) Some time between the present and 1500AD (about 15 generations back), you will most likely find that you are your own distant cousin--that the same person appears in multiple places in your tree. By about 1000AD (about 30 generations back), you'll have _MANY_ such duplications. If the tree/graph were printed on paper, it would resemble more of a kite or diamon with you at left end and Adam and Eve at the right end. In many cases, there will be multiple points in time where the number of unique ancestors hits a local maximum. > Brian Pears has written some interesting articles on the subject: > > http://www.bpears.org.uk/Misc/AncestorParadox/ Yes, that's kind-of what he says, too. -- Robert Riches [email protected] (Yes, that is one of my email addresses.)