During which geological epoch did the first monkeys reach South America?

The correct response is based on the timing of when the first monkeys are believed to have migrated to South America, which is attributed to the Oligocene epoch, approximately 35 to 23 million years ago. This period is significant for the evolution and dispersal of primates, as it marks the appearance of the first true monkeys in the fossil record.

Evidence suggests that these early New World monkeys likely arrived from Africa, possibly by way of land bridges or floating vegetation, as the Atlantic Ocean was narrower during the Oligocene than it is today. This epoch saw an increase in biodiversity and the establishment of various ecological niches, facilitating the adaptation and evolution of these primates in the new environment.

The other geological epochs mentioned do not align with this event. The Eocene, which predates the Oligocene, was characterized by early primate developments but not specifically by the emergence of monkeys in South America. The Miocene is important for later primate evolution, including the diversification of species, but occurs after the initial arrival of monkeys. The Pleistocene, known for its glacial periods, is too recent for the initial colonization of monkeys in South America, as they had already established themselves by that time.