The Universal Constructors are descendants of machines created by humans of an alternate timeline of the Time Ships Universe. In this timeline, humans from an alternate 1944 were stranded in the Palaeocene era, and thus had far more time to evolve than humans of our time period. These humans built machines with artificial intelligence to explore the stars. This exploration continued long after the extinction of humanity, with the machines continuing on in their search for knowledge. This eventually culminated in the creation of the Time Ships, largely made of Constructors themselves, with a goal of exploring back to the beginnings of our universe. They eventually colonized their whole multiverse.