Here's why:
* Ancient Lineage: Prosimians represent a very ancient lineage of primates, with their evolutionary history dating back millions of years.
* Simpler Features: They exhibit more "primitive" features compared to monkeys, apes, and humans, including:
* Smaller brain size
* Larger reliance on smell
* More primitive dentition
* Nocturnal habits (in many species)
* Grooming claws (in some species)
* Diverse Group: The prosimian group includes a variety of species, such as lemurs, lorises, and tarsiers.
It's important to note that:
* Primate evolution is complex: Determining the "most primitive" can be subjective, as evolution is a branching process.
* All primates are related: While prosimians are considered more primitive, they are still closely related to other primates, including humans.
Therefore, while prosimians are generally considered the most primitive primates, it's essential to understand the nuances of primate evolution and the interconnectedness of all primate species.