What group of primates is believed to include the first true anthropoids based on fossil evidence?

The group of primates believed to include the first true anthropoids, based on fossil evidence, is the basal anthropoids. This group is significant because it represents an early stage in primate evolution, particularly during the Eocene epoch when the ancestors of modern anthropoids began to appear.

Fossil findings indicate that these early anthropoids, which include species that are ancestral to both Old World monkeys and New World monkeys, displayed critical adaptations that distinguished them from earlier primate forms. These adaptations include traits such as increased brain size and changes in dental patterns that align with the characteristics of higher primates.

Understanding the role of basal anthropoids in the evolutionary tree is essential because it helps clarify the transition from earlier primate groups to the more derived forms that we see today. This knowledge not only sheds light on the evolution of primates but also on aspects of human evolutionary history as our lineage is closely related to anthropoids.

In contrast, Old World monkeys, large apes, and New World monkeys represent more derived groups that evolved later, building on the foundational characteristics established by basal anthropoids. Therefore, recognizing the importance of basal anthropoids is crucial in studying the evolutionary history of primates and understanding the lineage leading to modern humans.