Complex sentence: Between 1957 and 1967, he first was a research social scientist in the Mental Health Research Institute at the University of Michigan, focusing on systems theory, and then a professor in Michigan's department of natural resources, School of Conservation.
Split into simpler sentences: Between 1957 and 1967, he first was a research social scientist in the Mental Health Research Institute at the University of Michigan, focusing on systems theory. Later he became professor in Michigan's department of natural resources, School of Conservation.