I scanned through Wiki.
Summers got his PhD at age 27 (not the youngest).
He became a tenured full professor of economics at Harvard at age 28 - which was the youngest STEM professor in modern times.
Remarkably, Summers is now back at Harvard, as a full professor and the Director of an endowed “Center” at the Kennedy School of Government.
Thanks,my source was wrong!
“He became a tenured full professor of economics at Harvard at age 28 - which was the youngest STEM professor in modern times.”
Economics is not STEM.