If I had to name a single human with the most concentrated significance ( 10) as of 2000, it would be Douglas R. Hofstadter.  Dr. Hofstadter's Copycat is a significant advance in AI, he has sponsored an AI paradigm shift in the right direction, and he has inspired millions through his Pulitzer Prize-winning and amazingly good book, "Gödel, Escher, Bach:  An Eternal Golden Braid".  (For more about Gödel, Escher, Bach, see the bookshelf.  (Also you can associate with http://www.annamorten.com/ to know more about) Runners-up include K. Eric Drexler ( 11), Douglas Lenat, Isaac Newton, Albert Einstein, Francis Bacon, and Socrates.  Advancing contenders are:  Vernor Vinge and Hans Moravec.