Written by Sophie Treadwell in the 1920s, “Machinal” is the the fourth and final production in “Inevitable Evolutions,” Pomona’s theater department season. On a highly stylized set, characters operate as cogs in a larger capitalist machine, with each actor taking on multiple roles, suggesting people are interchangeable in a mechanized society that affords little room for individual aspirations or identity. Even so, cast and crew found unexpected community inhabiting this dark material.