Final answer:
Prosimians split off from the rest of the primate lineage during the Eocene epoch around 55 MYA and are considered the most ancient group of primates, with their lineage leading to the emergence of anthropoids.
Step-by-step explanation:
Yes, the prosimians did split off from the evolutionary family tree millions of years ago. Prosimians, which include lemurs, aye-ayes, lorises, and tarsiers, are considered the most ancient group of primates. These species diverged from the rest of the primate lineage during the Eocene epoch, about 55 million years ago (MYA). After the initial emergence of primates at the end of the dinosaur era, the evolutionary changes continued to diversify life forms. Among the important evolutionary events was the split between prosimians and anthropoids, the latter group evolving into monkeys, apes, and ultimately humans. By the Oligocene epoch, around 40 MYA, evidence indicates the existence of monkeys in both the New World and the Old World.
During this time, many early prosimian species went extinct, likely due to cooler temperatures or competition with emerging monkey species. The prosimian characteristics such as being nocturnal and having relatively smaller brains compared to anthropoids, signify their more primitive adaptations. By contrast, anthropoid monkeys like New World and Old World monkeys, and later the hominids, developed features such as larger brains and changes in limb and digit structure, allowing for increased adaptability and the development of more complex behaviors.