Complex sentence: After completing secondary school at the Liceo Aleman de Santiago (1951--1963), like his mentor Humberto Maturana, Varela studied first medicine then biology at the University of Chile, then did a Ph.D. in biology at Harvard University.
Split into simpler sentences: After completing secondary school at the Liceo Aleman de Santiago (1951--1963). Like his mentor Humberto Maturana, Varela first studied medicine then biology at the University of Chile, then did a Ph.D. in biology at Harvard University.