Monkeys, apes, and humans are collectively known as anthropoids or
“higher primates.” Compared to prosimians, living anthropoids possess

larger brains, eye sockets that are almost completely surrounded by bone,
a single lower jaw bone (or mandible) formed by the fusion of two separate
bones at the chin, and many other anatomically advanced features.
In terms of their behavior, anthropoids again differ from most prosimians,
although there is some overlap between species of each group. In
general, anthropoids tend to live in complex groups characterized by intricate
social interactions among individual members. Some prosimian
species, in contrast, live quite solitary lives. All anthropoids aside from
the South American owl monkey (Aotus) are diurnal—that is, they are
mainly active during daytime. Many prosimians, notably tarsiers, bushbabies,
lorises, and some lemurs, strongly prefer to move about and feed
at night. These profound differences between prosimians and anthropoids
extend to the molecular level. Analyses of long sequences of the DNA of
various species of monkeys, apes and humans show that all of these species
are far more similar to one another than any of them are to prosimians.
In an evolutionary context, this means that, whether we analyze anatomy,
behavior, or DNA, the conclusion remains inescapable. We humans are
much more closely related to monkeys and apes than we are to lemurs
or tarsiers. Put slightly differently, monkeys share a more recent common
ancestor with us than they do with prosimians.