Ask Marilyn ® by Marilyn vos Savant is a column in Parade Magazine, published by PARADE, 711 Third Avenue, New York, NY 10017, USA. According to Parade, Marilyn vos Savant is listed in the "Guinness Book of World Records Hall of Fame" for "Highest IQ."
In her Parade Magazine column of May 18, 1997 reports that some people can detect as many as 10,000 different smells, but neglects to tell us how many different scents are known to mankind.
Charlie Kluepfel <ChasKlu@aol.com> wrote to complain that you have failed to answer the question. Can every person who can detect as many as 10,000 different smells detect precisely the same set of 10,000? If each person's set is different, than there are more than 10,000 different smells known to mankind.
Another consideration is that some of the scents "known to mankind" may be detectable only in the laboratory, and that using laboratory equipment, the number of scents "known to mankind" may far surpass the number that people can detect with their noses.