Louis Bolk (1866-1930) was a professor of anatomy and embryology at the University of Amsterdam. He developed and employed comparative scientific methods of investigation that conveyed new insights into his subjects such as the principle of neoteny.
Neoteny describes how certain characteristics in the human organism rather stay underdeveloped compared to for instance the apes, remaining true to their embryological shape. Good examples are the relative embryologic shape of the head and the relative position of the foramen magnum in humans compared to the apes. With the insights he gained, he could put his subjects into a meaningful context.
To employ his method, he instructed his students to use the macroscope rather than the microscope!
Young and adult ape skull
Adult human and ape skull and skeleton.
Position of the foramen magnum of the skull.