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!