Which event marks the late Miocene period in primate evolution?

The late Miocene period is characterized by significant changes in the environment and the primate population. The correct answer highlights that as habitats transformed, particularly due to climatic shifts and the expansion of grasslands over forests, apes became rarer. This period also saw the decline of many ape species that were well-adapted to the forest environment as their habitats diminished. This dramatic shift in ecosystems impacted the survival of certain primate lineages, leading to increased competition among species and paving the way for evolutionary changes that would eventually lead to the emergence of hominins.

In contrast, the other options do not accurately reflect this period’s impact on primate evolution. While the extinction of certain species can occur in response to environmental changes, it does not encapsulate the nuanced dynamics of the late Miocene. The expansion of forests does not align with evidence from this period, as the habitat transformation leaned more towards the development of open grassland ecosystems. Lastly, the emergence of bipedal humans is more accurately linked to later periods, particularly the Pliocene, rather than the late Miocene, where the adaptations for bipedalism had not yet fully developed in hominins.