Tuesday, March 20, 2012

On Cousinhood

               On Cousinhood

               Assured of your supremacy?
               Oh silly sibling, don't be smug!
               For great and wide's our family tree;
               Dear sister seaweed, brother bug!

            First cousins are those who share a grandparent; second cousins share a great-grandparent; in general Nth cousins share an great^(N-1)-grandparent; or in other words share a parent N+1 generations back.  Therefore siblings are zeroth cousins, and one is one’s own negative first cousin!
            For what value of N are all human beings Nth cousins? This is a matter of evolutionary history. The present human species is about 200,000 years old, and at about 20 years per generation, that comes to 10,000 generations; so I would guess that we are at most 10,000ths cousins of each other; and probably much less.  There is some genetic evidence of genetic bottlenecks in human prehistory; so I would guess that we are at most 7000th cousins of each other, probably much less.
            And what of other species? I found the following figures at the site   www.evogeneao.com

            chimp        =  240,000th cousin
            gorilla        = 310,000th cousin
            cat            =  27,000,000th cousin
            cow          =  28,000,000th cousin
            robin         = 170,000,000th cousin
            frog          =  175,000,000th cousin
            fish           =  195,000,000th cousin
            snail         = 300,000,000th cousin
            dragonfly  = 300,000,000th cousin
            octopus    = 300,000,000th cousin

            According to that website, one can’t properly define cousinhood for bacteria. If we did, then I suppose that we’d be zillionth cousins to redwood and mildew, for some absurdly high value of zillion.
            In any case, it’s nice to have such a big and talented family.  Blessings, cousins!

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