In the northern hemisphere, evidence of the ice age lie all
about us, but it took someone with curiosity and imagination to
see this because so much has changed since then, and because human
hearts and minds are not sympathetic to that larger and more
dangerous world. In addition to curiosity and imagination, Louis
Agassiz also had the intelligence, passion, and persistence to
document the effects sufficiently to convince others.
But there are limits. Agassiz resisted Darwin’s
theories of evolution all his life.
See also in The book of science:
Readings on wikipedia: