Almost 90% of the scientists who ever lived are now alive.
Since about Issac Newton's time (1642 - 1727), knowledge has doubled almost every 17 years. The growth of the number of scientists generally has similarly been exponential, and it is said that currently, almost ninety percent of the scientist who ever lived are now alive.
In the book, Richard Hamming had a detailed demonstration on how he proved the statement to be true by solving the Exponential Growth Model equation y(t) = ae^(bt) where y(t) is the number of scientists at any time t and assuming the average scientist can live up to 55 years old.